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Euphausia pacifica and other euphausiids in the coastal waters of British Columbia: relationships to… Regan, Lance 1968

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EUPHAUSIA PACIFICA AND OTHER EUPHAUSIIDS IN THE COASTAL WATERS OF BRITISH COLUMBIA: RELATIONSHIPS TO TEMPERATURE, SALINITY AND OTHER PROPERTIES IN THE FIELD AND LABORATORY. by LANCE REGAN B. Sc., The University of B r i t i s h Columbia, 1960 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY In the Department of 'ZOOLOGY and INSTITUTE OF OCEANOGRAPHY We accept th i s thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA September, 1968 In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f t h e r e q u i r e m e n t s f o r a n a d v a n c e d d e g r e e a t t h e U n i v e r s i t y o f B r i t i s h C o l u m b i a , I a g r e e t h a t t h e L i b r a r y s h a l l m a k e i t f r e e l y a v a i l a b l e f o r r e f e r e n c e a n d S t u d y . I f u r t h e r a g r e e t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y p u r p o s e s may b e g r a n t e d b y t h e H e a d o f my D e p a r t m e n t o r b y h i s r e p r e s e n t a t i v e s . I t i s u n d e r s t o o d t h a t c o p y i n g o r p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l n o t b e a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . T h e U n i v e r s i t y o f B r i r i s h C o l u m b i a V a n c o u v e r 8, C a n a d a D e p a r t m e n t o f D a t e ( f c M ^ /£ Chairman: Professor Brian McK. Bary i ABSTRACT During 1960-61 the abundance and d i s t r i b u t i o n s of four species of euphausiids (Euphausia p a c i f i c a Hansen, Thysanoessa  s p i n i f e r a Holmes, Thysanoessa longipes Brandt and Thysanoessa  r a s c h i i M. Sars) and the developmental stages of one species, E. p a c i f i c a were studied each month i n r e l a t i o n to temperature and s a l i n i t y i n Indian Arm, Brit s h Columbia, using the method of T-S-P diagrams. Euphausia p a c i f i c a probably i s a resident species and as such was the most tolerant towards environmental conditions and t h e i r fluctuations i n Indian Arm, followed i n order of de-creasing tolerance by the expatriate species T. s p i n i f e r a , T. longipes and T. r a s c h i i . A l l species,(whether resident or expat-r i a t e s ) , were useful b i o l o g i c a l indicators of oceanographic changes i n Indian Arm, p a r t i c u l a r l y with reference to the detec-t i o n of outside waters entering the i n l e t . F i e l d data indicated that temperature and s a l i n i t y may have been contributory "regulatory factors" with regard to the v e r t i c a l d i s t r i b u t i o n of euphausiids i n Indian Arm, p a r t i c u l a r l y i n the region of maximum temperature and s a l i n i t y change i n the thermocline and halocline, between about 10 m and the surface. In contrast, the occurrences and d i s t r i b u t i o n of euphausiids i n intermediate-depth and deeper waters and the general absence of adult specimens of E. p a c i f i c a , T. s p i n i f e r a and T. longipes from the deep waters, below 120 m, and of T. r a s c h i i from waters below 60 m have suggested that regulatory factors other than temperature and s a l i n i t y were also operative. Nauplii and metanauplii of E. p a c i f i c a were markedly r e s t r i c t e d i n t h e i r i i d i s t r i b u t i o n to deeper water when compared with the broad v e r t i c a l d i s t r i b u t i o n of eggs, l a t e r developmental stages (cal y p t o p i i , f u r c i l i a ) and the adults of t h i s species, a feature which may be s i m i l a r l y caused. In the laboratory, experiments were conducted i n attempts to determine i f the variations i n euphausiid d i s t r i -butions found i n the f i e l d resulted from d i f f e r e n t reactions of species to temperature, s a l i n i t y and/or combinations of temperature-salinity, or to some other property or properties acting within p a r t i c u l a r temperature-salinity ranges. In the laboratory specimens were induced to migrate v e r t i c a l l y i n temperature which increased and s a l i n i t y which decreased towards the surface. The numbers migrating decreased progressively with increase i n the temperature and with decrease i n the s a l i n i t y . The strongest effects occurred when the rate of change of either property was the maximum obtainable and when temperature and s a l i n i t y gradients were combined. These experiments indicated, also, that specimens would migrate into higher temperatures and lower s a l i n i t i e s than usually obtained i n the f i e l d (and t h i s , despite the much steeper gradients employed i n the laboratory). In a second series of experiments temperature and s a l i n i t y conditions were kept constant, or nearly so, and specimens (of E. p a c i f i c a) were induced to migrate from water or i g i n a t i n g i n one area ("home') into water from another area ("foreign"). In general, specimens showed a preference towards the properties of "home" water and would "avoid" the "foreign" waters. In survival experiments specimens survived i n larger numbers and for longer periods i n "home" waters than i n "foreign" waters or i n mixtures of the two. There were indications of a seasonal f l u c t u a t i o n i n survival of specimens^' -On the basis of the findings from the f i e l d and labora-tory investigations, i t i s postulated that properties unique to di f f e r e n t waters, and the reaction of euphausiids towards these "unique properties", were important i n the occurrences and d i s -t r i b u t i o n of euphausiids i n Indian Arm and t h e i r migration and survival i n the laboratory. i v TABLE OF CONTENTS Page I. INTRODUCTION 1 PART A: FIELD PROGRAMME 6 I I . MATERIALS AND METHODS 7 COLLECTION OF DATA 7 I I I . OCEANOGRAPHIC CONDITIONS 12 DISTRIBUTION OF TEMPERATURE, SALINITY AND DENSITY (O t) 13 DISCUSSION OF TEMPERATURE, SALINITY AND DENSITY . . . 28 IV. TEMPERATURE, SALINITY AND THE OCCURRENCES OF EUPHAUSIIDS 35 Euphausia p a c i f i c a 37 Adults 37 Discussion of adults of Euphausia p a c i f i c a 43 Developmental stages of Euphausia pacif i c a 47 Eggs 47 Nauplius I 48 Nauplius II 49 Metanauplius 50 Calyptopis I, II and III .51 F u r c i l i a I, III and VI.... 53 Discussion of the developmental stages of Euphausia p a c i f i c a 55 Thysanoessa s p i n i f e r a 58 Discussion of Thysanoessa s p i n i f e r a . . . . . . . . 63 Thysanoessa longipes 67 Discussion of Thysanoessa longipes 71 Thysanoessa r a s c h i i 74 Discussion of Thysanoessa r a s c h i i . . . . 75 TABLE OF CONTENTS (continued) v Page V. VERTICAL MIGRATION OF EUPHAUSIA PACIFICA IN RELATION TO TEMPERATURE AND SALINITY; PRELIMINARY OBSERVATIONS IN INDIAN ARM 79 PART B : LABORATORY PROGRAMME 81 VI. MATERIALS AND METHODS 83 COLLECTIONS OF SPECIMENS AND WATER 83 TERMS USED IN DESCRIBING EXPERIMENTAL OBSERVATIONS. . 85 VERTICAL MIGRATION IN THE LABORATORY 87 Migration i n s a l i n i t y structures 88 Migration i n temperature structures 90 Migration i n combined temperature and s a l i n i t y structures 92 Migration i n "home" and "foreign" waters . . . . 93 SURVIVAL IN THE LABORATORY 94 Survival i n di l u t e d seawater 95 Survival i n "home" and "foreign" waters . . . . 96 VII. EXPERIMENTAL RESULTS 99 VERTICAL MIGRATION OF EUPHAUSIIDS IN RELATION TO SALINITY: EXPERIMENTAL OBSERVATIONS . 99 Behaviour during migrations: 99 a. i n constant temperature and s a l i n i t y (control) 99 b. i n a s a l i n i t y structure, at constant temperature 99 V e r t i c a l migration of„JBuphausia p a c i f i c a : . . . 101 a. i n a s a l i n i t y structure at constant temperature 101 b. Migrations i n r e l a t i o n to maximal and  minimal s a l i n i t i e s 103 V e r t i c a l migration of Euphausia p a c i f i c a , Thysanoessa s p i n i f e r a and Thysanoessa longipes i n a s a l i n i t y structure 104 VERTICAL MIGRATION OF EUPHAUSIIDS IN RELATION TO TEMPERATURE: EXPERIMENTAL OBSERVATIONS 105 TABLE OF CONTENTS (Continued) v i VII. EXPERIMENTAL RESULTS (Continued) page Behaviour during migrations: 106 a. i n constant temperature and s a l i n i t y  (control) 106 b. i n changing temperature and constant s a l i n i t y 106 V e r t i c a l migration of Euphausia p a c i f i c a and Thysanoessa s p i n i f e r a i n a temperature structure with constant s a l i n i t y 107 VERTICAL MIGRATION OF EUPHAUSIA PACIFICA IN RELATION TO COMBINED TEMPERATURE AND SALINITY: 108 a. Experimental 108 b. Comparison of laboratory results and f i e l d observations 110 VERTICAL MIGRATION OF EUPHAUSIA PACIFICA IN "HOME" AND "FOREIGN" WATERS: EXPERIMENTAL OBSERVATIONS 115 SURVIVAL OF EUPHAUSIA PACIFICA IN THE LABORATORY IN DILUTIONS OF INDIAN ARM WATER 119 SURVIVAL OF EUPHAUSIA PACIFICA IN THE LABORATORY IN "HOME" AND "FOREIGN" WATERS 120 a. Survival i n "home" water (Indian Arm) and  i n waters from S t r a i t of Georgia, Juan de Fuca S t r a i t and Malaspina S t r a i t 120 b. Survival i n "home" water (Juan de Fuca  S t r a i t ) and i n waters from S t r a i t of Georgia and Indian Arm. 123 c. Survival i n "home" water ( S t r a i t of Georgia) and i n water from Indian Arm 124 DISCUSSION- OF SURVIVAL IN THE LABORATORY 126 VIII. DISCUSSION^., 134 IX. SUMMARY AND CONCLUSIONS 154 X. "LITERATURE CITED" 159 v i i ' LIST OF TABLES Table Subject Page ll- The maximum and minimum temperature, s a l i n i t y and oxygen values recorded i n Indian Arm from January, 1960, through August, 1961 164 2. Euphausia pac i f i c a , no. / m 165 3. Thysanoessa s p i n i f e r a , Thysanoessa longipes,  Thysanoessa r a s c h i i , no. /10 cu. m 166 4. The maximum and minimum values of temperature and s a l i n i t y i n which the developmental stages of Euphausia p a c i f i c a were c o l l e c t e d i n Indian Arm, from September, 1960 to July-August, 1961 167 5. The maximum and minimum values of temperature and s a l i n i t y i n which adult specimens of Euphausia  p a c i f i c a , Thysanoessa s p i n i f e r a , Thysanoessa  longipes and Thysanoessa r a s c h i i were c o l l e c t e d i n Indian Arm. January, 1960 to July-August,1961 . . 168 6. The v e r t i c a l migration of Euphausia p a c i f i c a i n r e l a t i o n to s a l i n i t y when varying temperature structures are superimposed upon si m i l a r s a l i n i t y structures 169 7. The v e r t i c a l migration of Euphausia p a c i f i c a i n r e l a t i o n to temperature, when s a l i n i t y structures are superimposed upon temperature structures. . . . 170 8. Survival i n the laboratory of Euphausia p a c i f i c a i n "home" water (Indian Arm) and i n "foreign" waters ( S t r a i t of Georgia, Juan de Fuca S t r a i t and Malaspina S t r a i t ). Euphausiids c o l l e c t e d i n Indian Arm 171 9. Survival i n the laboratory of Euphausia p a c i f i c a i n "home" and "foreign" waters. Euphausiids  c o l l e c t e d i n Juan de Fuca S t r a i t 172 10. Survival i n the laboratory of Euphausia p a c i f i c a i n "home" and "foreign" waters. Euphausiids  c o l l e c t e d i n the S t r a i t of Georgia. 173 v i i i LIST OF FIGURES Figure Subject Page 1. Indian Arm, B r i t i s h Columbia, and adjacent regions. 174 2. Mean temperature-salinity (T-S) curves for the period from September, 1960, to July-August, 1961, for those standard depths applicable at stations 2, 6, 9, 12, 15 and 23 175 3-17. Temperature-salinity diagrams of Indian Arm for January, 1960, to July-August, 1961. Inserts show isotherms (a) and isohalines (b) i n longitudinal 176-sections of the i n l e t 183 18-20. Fluctuations i n the d i s t r i b u t i o n of density i n Indian Arm as shown by the three selected isopyc-nals of c?t 19.5, 20.75 and 21.0, between January, 184-1960, and July-August, 1961 186 21-27. Temperature-salinity-plankton (T-S-P) diagrams of Indian Arm i n which the occurrences of adults, eggs, n a u p l i i , metanauplii, c a l y p t o p i i and f u r c i l i a of Euphausia p a c i f i c a , and the adults of Thysanoessa  s p i n i f e r a , Thysanoessa longipes and Thysanoessa  r a s c h i i are shown i n r e l a t i o n to t o t a l ranges of temperature (°C) and s a l i n i t y (°/oo) for the period 187-from September, 1960, to July-August, 1961 193 28. The geographical occurrences of adults of Euphausia  p a c i f i c a (a), Thysanoessa s p i n i f e r a (b),Thysanoessa  longipes (c) and Thysanoessa r a s c h i i (d) i n longitud-i n a l sections of Indian Arm for the period from September, 1960, through July-August, 1961 194 29. The geographical occurrences of the developmental stages (eggs (a); f i r s t (b) and second (c) nauplius stages; metanauplius (d); f i r s t , second and t h i r d calyptopis stages (e); and f i r s t , t h i r d and s i x t h f u r c i l i a stages (f) of Euphausia p a c i f i c a i n l o n g i -tudinal sections of Indian Arm for the period from September, 1960, through July-August, 1961 195 30-44. Temperature-salinity-plankton (T-S-P) diagrams showing night (blocked-in c i r c l e s ) and day (open c i r c l e s ) occurrences of adults of Euphausia p a c i f i c a i n r e l a t i o n to temperature and s a l i n i t y for monthly 196-i n t e r v a l s , from January, 1960,to July-August,1961. . 203 ix LIST OF FIGURES (Continued) Figure Subject Page 45. (a-o) Longitudinal sections of Indian Arm showing occurrences during the night (blocked-in c i r c l e s ) and day (open c i r c l e s ) of adults of Euphausia '.gacifica, between January, 1960, and July-August, 19.61 .... '. 204 46-49. Temperature-salinity-plankton (T-S-P) diagrams of Indian Arm showing occurrences of eggs of 205-Euphausia p a c i f i c a from March to July-August,1961.. 206 50-52. Temperature-salinity-plankton (T-S-P) diagrams of Indian Arm showing the night (blocked-in c i r c l e s ) and day (open c i r c l e s ) occurrences of the f i r s t nauplius stage of Euphausia p a c i f i c a from A p r i l to 207-July-August, 1961 208 53-55. Temperature-salinity-plankton (T-S-P) diagrams of Indian Arm showing the night (blocked-in c i r c l e s ) and day (open c i r c l e s ) occurrences of the second nauplius stage of Euphausia p a c i f i c a 209-from A p r i l to July-August, 1961 210 56-58. Temperature-salinity-plankton (T-S-P) diagrams of Indian Arm showing the night (blocked-in c i r c l e s ) and day (open c i r c l e s ) occurrences of metanauplius of Euphausia p a c i f i c a from A p r i l 211-to July-August, 1961 212 59-62. Temperature-salinity-plankton (T-S-P) diagrams of Indian Arm showing the night (blocked-in c i r c l e s ) and day (open c i r c l e s ) occurrences of the f i r s t calyptopis stage of Euphausia p a c i f i c a 213-for September, 1960 and A p r i l to July-August,1961.. 214 63-66. Temperature-salinity-plankton (T-S-P) diagrams of Indian Arm showing the night (blocked-in c i r c l e s ) and day (open c i r c l e s ) occurrences of the second calyptopis stage of Euphausia p a c i f i c a 215-for September,I960, and A p r i l to July-August,1961.. 216 67-70. Temperature-salinity-plankton (T-S-P) diagrams of Indian Arm showing the night (blocked-in c i r c l e s ) and day (open c i r c l e s ) occurrences of the t h i r d calyptopis stage of Euphausia p a c i f i c a 217-for October,1960 and A p r i l to July-August,1961. . . 218 71-74. Temperature-salinity-plankton(T-S-P) diagrams of Indian Arm showing the night (blocked-in c i r c l e s ) and day (open c i r c l e s ) occurrences of the f i r s t f u r c i l i a stage of Euphausia p a c i f i c a for September, 219-'•••t 1960, and A p r i l to July-August, 1961 220 X LIST OF FIGURES (Continued) Figure Subject Page 75-78. Temperature-salinity-plankton (T-S-P) diagrams of Indian Arm showing the night (blocked-in c i r c l e s ) and day (open c i r c l e s ) occurrences of the t h i r d f u r c i l i a stage of Euphausia p a c i f i c a for September, 1960, and A p r i l to 221-July-August, 1961 222 79-82. Temperature-salinity-plankton (T-S-P) diagrams of Indian Arm showing the night (blocked-in c i r c l e s ) and day (open c i r c l e s ) occurrences of the si x t h f u r c i l i a stage of Euphausia p a c i f i c a for September and October,1960, and 223-June and July-August, 1961 224 83-97. Temperature-salinity-plankton (T-S-P) diagrams of Indian Arm showing night (blocked-in c i r c l e s ) and day (open c i r c l e s ) occurrences of adults of Thysanoessa s p i n i f e r a i n r e l a t i o n to temperature and s a l i n i t y fdn monthly i n t e r v a l s , from January, 225-j. •:, I960, t o July-Augus t , c 1961 232 98(a-o). Longitudinal sections of Indian Arm showing occurrences during the night (blocked-in c i r c l e s ) and day (open c i r c l e s ) of adults of Thysanoessa spinifera,between January, 1960, and July-August 1961 233 99-111. Temperature-salinity-plankton (T-S-P) diagrams showing night (blocked-in c i r c l e s ) and day (open c i r c l e s ) occurrences of adults of Thysanoessa longipes i n r e l a t i o n to temperature and s a l i n i t y for monthly i n t e r v a l s , from January, 1960 to 234-July-August, 1961 240 112(a-o). Longitudinal sections of Indian Arm showing occurrences during the night (blocked-in c i r c l e s ) and day (open c i r c l e s ) of adults of Thysanoessa longipes,between January, 1960, and July-August, 1961 241 113-117. Temperature-salinity-plankton (T-S-P) diagrams showing night (blocked-in c i r c l e s ) and day (open c i r c l e s ) occurrences of adults of Thysanoessa r a s c h i i i n r e l a t i o n to temperature and s a l i n i t y for July, September, October and December, i960, 242-and July-August, 1961 244 x i LIST OF FIGURES (Continued) Figure Subject Page 118-120. Temperature and s a l i n i t y structures i n Indian Arm with respect to the v e r t i c a l d i s t r i b u t i o n and abundance of Euphausia p a c i f i c a at Station 9, night and day c o l l e c t i o n s combined, for 245-February, March and June, 1961 247 121-123. Photographs of apparatus used i n observing the migration of euphausiids i n temperature and 248-s a l i n i t y structures i n the laboratory 250 124. V e r t i c a l migration i n the laboratory of Euphausia p a c i f i c a from Indian Arm, i n s a l i n i t y structures composed of "home" water (Indian Arm) and of <>." foreign" waters ( S t r a i t of Georgia, Juan de Fuca S t r a i t ) . Mean s a l i n i t y gradient of 0.4 °/oo/cm; temperature constant 251 125. V e r t i c a l migration i n the laboratory of Euphausia p a c i f i c a , adults and f u r c i l i a , from Indian Arm i n a s a l i n i t y structure composed of Indian Arm water 252 126. V e r t i c a l migration i n the laboratory of Euphausia p a c i f i c a from Indian Arm i n r e l a t i o n to rate of change i n s a l i n i t y structures . . . . 2533 127. A composite diagram showing the maximum and minimum s a l i n i t i e s i n r e l a t i o n to the v e r t i c a l migration of adult Euphausia pa c i f i c a . i n the laboratory 254 128. Comparison of the v e r t i c a l migration i n the laboratory of Euphausia p a c i f i c a and Thysanoessa  s p i n i f e r a from Indian Arm i n a s a l i n i t y struc-ture composed of Indian Arm water 255 129. V e r t i c a l migration i n the laboratory of Thysanoessa longipes from the S t r a i t of Georgia i n a s a l i n i t y structure composed of S t r a i t of Georgia water 256 130-131. V e r t i c a l migration i n the laboratory of Euphausia  p a c i f i c a from Indian Arm i n temperature structures257-composed of Indian Arm water. S a l i n i t y constant .258 x i i LIST OF FIGURES (Continued) Figure Subject Page 132. V e r t i c a l migration i n the laboratory of Thysanoessa s p i n i f e r a from Indian Arm i n a temperature structure composed of Indian Arm water. S a l i n i t y constant 259 133-135. V e r t i c a l migration i n the laboratory of Euphausia p a c i f i c a from Indian Arm i n combined temperature and s a l i n i t y structures composed 260-'.' of Indian Arm water 262 136. A summary diagram showing the e f f e c t on the v e r t i c a l migration of Euphausia pacifica,with respect to temperature, when s a l i n i t y structures are superimposed upon temperature structures . . . 263 137-138. Summary diagrams comparing the general occur-rences and the migrations of Euphausia p a c i f i c a with respect to temperature and s a l i n i t y i n 264-Indian Arm and i n the laboratory 265 139. V e r t i c a l migration i n the laboratory of Euphausia  p a c i f i c a i n "home" water (Indian Arm) and i n "foreign" water (Juan de Fuca S t r a i t ) , when neither temperature nor s a l i n i t y are l i m i t i n g . S a l i n i t i e s are indicated; temperature,10°C. . . . 266 140. V e r t i c a l migration i n the laboratory of Euphausia  p a c i f i c a i n "home" water (Juan de Fuca S t r a i t ) and i n "foreign" water (Indian Arm), when neither temperature nor s a l i n i t y are l i m i t i n g . S a l i n i t i e s are indicated; temperature, 10°C 267 141-142. Survival i n the laboratory of Euphausia p a c i f i c a 268-from Indian Arm i n d i l u t i o n s of Indian Arm water. 269 143-145. Survival i n the laboratory of Euphausia p a c i f i c a i n "home" water (Indian Arm) , "foreign" waters and i n mixtures of the two. Specimens i n Indian 270-Arm water act as a control 272 146. Survival i n the laboratory of Euphausia p a c i f i c a i n "home" water (Juan de Fuca S t r a i t ) and i n "foreign" waters. Specimens i n Juan de Fuca water (diluted and undiluted) act as controls. . 273 147. Survival i n the laboratory of Euphausia p a c i f i c a i n "home" water ( S t r a i t of Georgia) and i n "f o r -eign" water. Specimens i n S t r a i t of Georgia act as a control 274 ACKNOWLEDGEMENTS x i i i I would l i k e to express my most sincere thanks to my research advisor, Dr. B. McK. Bary foijhis c r i t i c i s m , patience, and i n p a r t i c u l a r , h i s encouragement offered i n the writing of th i s t h e s i s . I am also indebted to the members of my research committee, Dr. G. L. Pickard, Dr. W. S. Hoar and Dr. N. J . Wilimovsky, a l l of whom read and constructively c r i t i c i z e d the t h e s i s . J . Fulton of the P a c i f i c B i o l o g i c a l Station, Nanaimo, B.C., provided unpublished data of the c o l l e c t i o n of Thysan-oessa r a s c h i i i n the S t r a i t of Georgia, for which many thanks are due. The Ins t i t u t e of Oceanography, U. B. C. provided the material, f a c i l i t i e s and technical people for t h i s study. The Ins t i t u t e of Oceanography and the National Research Council of Canada provided f i n a n c i a l assistance for the study. I would l i k e to thank the masters, o f f i c e r s and men of C.S.S.EHKOLI, C.N.A.V. WHITETHROAT and C.N.A.V. OSHAWA for t h e i r capable assistance i n the c o l l e c t i o n of the data. A special thanks to Miss E. Player who, on very short notice, completed the typing of the th e s i s . To my wife, Bobbie, whose encouragement and determina-t i o n played a large r o l e i n the completion of the thesis, I am forever indebted. I. INTRODUCTION 1 A detailed study of the physical oceanography (Gilmartin, 1960, 1962) of Indian Arm, B r i t i s h Columbia, and investigations of d i s t r i b u t i o n s of selected species of zoo-plankton (McHardy, 1961; Shan, 1962) i n the i n l e t have been undertaken during the past several years by the Insti t u t e of Oceanography, University of B r i t i s h Columbia. The present study i s concerned with environmental factors involved i n the occurrences and d i s t r i b u t i o n of the euphausiids, Euphausia  p a c i f i c a Hansen, Thysanoessa s p i n i f e r a Holmes, Thysanoessa  longipes Brandt and Thysanoessa r a s c h i i M. Sars, i n Indian Arm and the migration and survival i n the laboratory of E_. p a c i f i c a from Indian Arm and adjacent areas i n waters of diverse o r i g i n . Taxonomic descriptions of the euphausiids investiga-ted i n the present study, along with general notes on t h e i r d i s t r i b u t i o n s i n the North P a c i f i c have been reported by Banner (1950) Boden, Johnson and Brinton (1955) and Brinton (1962); post-naupliar developmental stages of E_. p a c i f i c a have been described by Boden (1950). Euphausia p a c i f i c a and T. longipes appear to be primar-i l y oceanic species, widely d i s t r i b u t e d throughout the North P a c i f i c , but also occurring i n n e r i t i c waters; T. spinifera and r a s c h i i appear to be r e s t r i c t e d to waters along the coasts bordering the northeastern P a c i f i c . No information i s available i n the l i t e r a t u r e concerning detailed studies of either the d i s -t r i b u t i o n of euphausiids, or of factors involved i n t h i s , for 2 B r i t i s h Columbia. In B r i t i s h Columbia coastal waters E. p a c i f i c a , i s almost always the dominant species and can occur i n very large numbers. There i s a large body of l i t e r a t u r e a t t e s t i n g the importance of temperature and s a l i n i t y i n the physiological reactions of organisms towards marine and brackish-water environ-ments. Recent reviews of papers on or including the effects of temperature and s a l i n i t y on the metabolism, reproduction, develop-ment and a c t i v i t y of aquatic organisms have been provided by Prosser and Brown (1961) and Kinne (1963, 1964). These summarize the consensus of many workers that temperature and s a l i n i t y are probably two of the most important physical factors i n the l i f e of marine and brackish-water animals. Ekman (1953), Sverdrup, Johnson and Fleming (1942) and Hedgpeth (1957), among others,have divided the oceans and t h e i r faunas into horizontal (e.g.,boreal, temperate, A r c t i c ) and v e r t i c a l , (e.g.,epipelagic, bathypelagic, abyssal)zoogeographical zones dependent for t h e i r demarcation on temperature as shown by p a r t i c u l a r isotherms. Additional l i t e r a -ture concerns primarily the e f f e c t s of temperature on the v e r t i c a l d i s t r i b u t i o n of zooplankton (Moore, 1950, 1952; Moore, Owre, Jones and Dow, 1953; Moore and Corwin, 1956; Moore and Foyo, 1963). Several attempts have been made to c l a s s i f y marine and brackish waters and t h e i r faunas on differences i n average s a l i n i t y (Ekman, 1953; Hedgpeth, 1957). Lance (1962) demonstrated experimentally that s a l i n i t y per se ef f e c t s the v e r t i c a l migration and d i s t r i b u -t i o n of zooplankton and t h i s i s pertinent to the present study. It has been demonstrated i n recent studies dealing with 3 ef f e c t s of temperature and s a l i n i t y on reactions of organisms that both factors should be considered together, i n a b i f a c t o r -i a l approach (Kinne, 1964). Some of the data are derived from the su r v i v a l of marine and brackish-water animals i n the labora-tory (McLeese, 1956; and Costlow, Bookhout and Monroe, 1960, 1962). On the other hand Pickford (1946, 1952), Haffner (1952), David (1955, 1958), McGowan (1959) and Bary (1959, 1963 a, c and d, 1964) have developed and modified techniques of r e l a t i n g the d i s t r i b u t i o n of marine organisms i n the f i e l d to those bodies of water (water masses), characterized by t h e i r temperatures and s a l i n i t i e s by means of temperature-salinity (T-S) diagrams. B a s i c a l l y these techniques d i r e c t l y r e l a t e the occurrences of organisms to the temperature-salinity conditions i n which they are l i v i n g . There has been continuing speculation whether the tem-perature and/or s a l i n i t y (used to characterize the environmental water "bodies") i n fact "control" the occurrences and d i s t r i b u -t i o n of the organisms, or whether the "control" might be exercised by means of other factors i n c l u s i v e i n the "bodies" of water. Thus Bary (1963 a, 1964) has shown that d i s t r i b u t i o n s of pelagic organ-isms i n the northeastern A t l a n t i c were associated with i d e n t i f i -able bodies of water, but that neither the temperature nor the s a l i n i t y defining these waters appeared to be the factors respon-s i b l e for the p a r t i c u l a r species-water body associations. Other undetermined factors, the "unique properties" (Bary, 1963 a, p f64), were hypothesised as in t e g r a l to these water bodies, and that these combined with the differences i n "tolerance" among species, 4,. were responsible for the association between the species and the water-body. Wilson (1951) and Wilson and Armstrong (1952, 1954) were among the f i r s t investigators to demonstrate experimentally that " b i o l o g i c a l differences" existed between natural waters of diverse o r i g i n . In general these studies indicated that English Channel water (near Plymouth) either lacked some v i t a l substance, or contained i n minute amounts something harmful to the develop-ment and survival of c e r t a i n species of sea-urchins and polychaetes. In C e l t i c Sea and Clyde Sea water brought into the laboratory, development generally approached normal and the specimens survived considerably better than i n the water from the English Channel. More recently Johnston (1962, 1964) has demonstrated experiment-a l l y that the growth of phytoplankton can be affected favourably or adversely depending on the "quality" of seawaters from the North Sea and North A t l a n t i c . Seawater, as a natural medium for phyto-plankton, changed according to the location, depth and season at which the water was c o l l e c t e d . "Quality" might be traced to gross differences i n composition of the dissolved organic matter i n the respective waters (Johnston, 1962), and i n p a r t i c u l a r to the chelation of trace metals by dissolved organic substances (Johnston, 1964). It appears therefore that there i s a large body of f i e l d and experimental data concerned with the role of temperature and s a l i n i t y as the c o n t r o l l i n g processes of d i s t r i b u t i o n s of marine and brackish-water organisms. However, the importance of other undetermined factors (be they referred to as "unique properties" or " b i o l o g i c a l differences" or "qu a l i t i e s " ) i n seawater, and the 5 reactions of organisms to such factors, i s increasingly evident i n the more recent l i t e r a t u r e . The present study has consisted of two parts. F i r s t l y , an attempt has been made from f i e l d data to resolve whether, for the coastal waters of B r i t i s h Columbia, temperature and s a l i n i t y play a part i n the d i s t r i b u t i o n s of selected species and i f so to what extent t h i s applies. Secondly, from laboratory studies, i t has been desired to show whether other factors might be playing a primary or a secondary role and either control occurrences or modify the e f f e c t s of temperature and/or s a l i n i t y . On the basis of the evidence two general statements can be made. F i r s t l y , temperature and s a l i n i t y , p a r t i c u l a r l y when combined, can a f f e c t the v e r t i c a l d i s t r i b u t i o n and migration of specimens i n regions of extreme change (thermocline and halocline) both i n laboratory experiments and i n near-surface waters i n the f i e l d . Secondly, the e f f e c t s of temperature and s a l i n i t y (in intermediate-depth and deep waters of Indian Arm and i n seawaters of diverse origin) appeared to be secondary to other unidentified factors, p a r t i c u l a r l y when tests were c a r r i e d out between waters of diverse o r i g i n s . The evidence obtained tends to support Wilson et a l (1951, 1954) i n t h a t " b i o l o g i c a l differences" were demonstrated between waters from d i f f e r e n t , but on occasion adjacent areas i n B r i t i s h Columbia coastal waters. 6 PART A: FIELD PROGRAMME To determine the relationships between the d i s t r i b u t i o n of euphausiids and temperature and s a l i n i t y i n Indian Arm the following were studied: 1. the monthly d i s t r i b u t i o n a l patterns of four species, between January, 1960, and July-August,1961. 2. the monthly d i s t r i b u t i o n a l pattern of the develop-mental stages of Euphausia p a c i f i c a , between September, 1960, and July-August, 1961. 3. the monthly d i s t r i b u t i o n of temperature, s a l i n i t y and density (o't), and the movement of waters into and out of the i n l e t between January, 1960 and July-August, 1961. 4. the rel a t i o n s between the occurrences of euphausiids and the d i s t r i b u t i o n of temperature, s a l i n i t y and density (o't). 5. the relations between changes i n occurrences of euphausiids and concurrent changes i n oceanographic conditions indicated by temperature, s a l i n i t y and density (o't) • 7 I I . MATERIALS AND METHODS COLLECTION OF DATA Concurrent c o l l e c t i o n s of temperatures, s a l i n i t i e s and plankton were made i n Indian Arm at approximately monthly inter v a l s between June, I960, and July-August,1961 ( 1.0.U.B.C, 1960, 1961). To include periods i n which there were gross changes i n water conditions, as well as periods of r e l a t i v e s t a b i l i t y , i t was necessary to extend the investigation and to t h i s end data and samples c o l l e c -ted between January and A p r i l , 1960, were examined. During the monthly cruises, s i x selected stations were occupied during night and day. Four sampling runs of each were made i n which temperature, s a l i n i t y and plankton data were c o l l e c t e d ; during some additional runs, only plankton was c o l l e c t e d . Whenever possible, stations were sampled during both flood and ebb ti d e s . The s i x stations (Stations 2, 6, 9, 12, 15 and 23,Fig. la) were located along the mid-line of Indian Arm at the same positions as sampled by Gilmartin (I960), McHardy (1961) and Shan (1962). The positions, chosen with respect to the physio-graphy of and c i r c u l a t i o n i n the i n l e t , are believed to have provided representative data. They are situated(Fig.la) over the s i l l (Station 23) i n the deep basin (Stations 6 and 9),in shoaling waters (Stations 2 and 12), and i n a region of maximum mixing(Station 15). Exchanges of water between Indian Arm and Burrard Inlet occur through the positions of Stations 15 and 23. 8 During the present study, extensive fog i n December, 1960, and January, 1961, prevented ship manoeuvring i n the shallow and narrow regions of Station 23 and 1J5; p r i o r to the present study, Station 23 was not sampled i n January, February and March, 1960 (McHardy, 1961) . In A p r i l , 1961, no c o l l e c t i o n s were made during darkness. Standard oceanographic techniques were used. Water samples for s a l i n i t y and oxygen determinations were obtained using Atlas water bottles at the standard depths of 0, (5)^, 10, 2 0 , ( 3 0 ) 2 , 50, 75, 100, 150 and 200 m; i n s i t u temperatures were recorded using reversing thermometers. In addition, v e r t i c a l temperature-depth p r o f i l e s were obtained using the bathyther-mograph. S a l i n i t i e s were determined by the Mohr t i t r a t i o n method and oxygen content by the Winkler t i t r a t i o n method (for description of methods, see Strickland and Parsons, 1961) . Density was derived from temperature and s a l i n i t y by means of nomograph tables. The monthly presentations of temperature, s a l i n i t y and density (o't) (Figs. 3-20) for Indian Arm are the means of values from two sampling runs, one made during the flood and the other during the ebb of a t i d e . The plankton-sampling programme was designed to demon-strate the s p a t i a l , d i e l , and seasonal d i s t r i b u t i o n s of euphausiids i n Indian Arm. The plankton sampler was the Clarke-Bumpus Sampler (Clarke and Bumpus, 1950) , modified according to Paquette and Frolander (1956) and f i t t e d with 1. Depth of 5 m not sampled between January and A p r i l , 1960 2. Depth of 30 m not sampled between January and October, 1960. 9 nylon nets with mesh apertures of either 0.40 mm (No.2 mesh) or 0.12 mm (No. 10 mesh). During each cruise, nets of No. 2 mesh were used for the f i r s t 24-hour period and No.10 for the second. The No.2 mesh was used for c o l l e c t i n g adults euphausiids and No. 10 primarily for eggs and developmental stages. The plankton samplers were lowered closed to a series of selected depths, opened with a messenger, towed ho r i z o n t a l l y over a radar-measured distance of f i v e cables ( about 0.93 km), and f i n a l l y closed with a second messenger and retrieved. Duration of the tows was between 10 and 15 minutes at a speed of two to three knots. A Tsurumi-Seiki-Kosakusjo (T-S-K) maximum depth recorder was used on several occasions to check the depth of tow as calculated from the angle of the towing cable (Regan, 1963). A flow-meter present i n each plankton sampler enabled estimations to be made of the volume of water f i l t e r e d during a l l plankton tows. It was possible, therefore, to treat the plankton samples q u a n t i t a t i v e l y . Plankton was c o l l e c t e d from the estimated depths of 0, 30, 60, 90, 120, 150 and 180 m at Stations 2, 6, 9 and 12, when depth permitted. At Station 15, c o l l e c t i o n s were from 0, 30 and 50 m and, at Station 23, from 0 and 20 m. Additional samples were c o l l e c t e d from depths of 15 m (beginning i n February,1961), 45 m (beginning i n March, 1961), and 8 and 75 m (beginning i n June, 1961); t h i s extra sampling was introduced to provide more detailed information on the v e r t i c a l d i s t r i b u t i o n of the euphau-s i i d s i n the upper waters and was continued u n t i l July-August,1961. Information on whether euphausiids occurred near the bottom of Indian Arm. was based on c o l l e c t i o n s made from approximately one 10 metre above the bottom, October, 1960, *>bd July-August, 1961; a Clarke-Bumpus sampler was attached to a large, f l a t weight which was towed along the bottom. A secondary project, pertaining to the te s t i n g and evaluation of the Clarke-Bumpus Plankton Sampler i n the c o l l e c t i o n of euphausiids, was undertaken i n 1961. A f u l l report of t h i s study has been presented i n a manuscript report (Regan, 1963). A large number of plankton samples accumulated from the intensive sampling programme. It was necessary, therefore, to select samples for subsequent analysis. In general, the selected samples were those c o l l e c t e d concurrently with oceanographic data. To obtain more specimens of the less abundant species(Thysanoessa  longipes and T. r a s c h i i ) additional samples, from the runs i n which only plankton was c o l l e c t e d , were examined. Counts of the adults were r e s t r i c t e d to samples c o l l e c t e d with the 0.40 mm mesh and the developmental stages to c o l l e c t i o n s made with the 0.12 mm mesh. Plankton samples were fixed and preserved i n a 1:10 solution of 40 % neutralized formalin and seawater. A l l adult euphausiids were removed from the sample, sorted for species and counted. A vacuum-assisted subsampler (McHardy, 1964) was used to obtain a 10 % subsample, from which the developmental stages were sorted to species and growth stages and counted. Results of analyses are reported as numbers c o l l e c t e d per cubic metre of water f i l t e r e d for Euphausia p a c i f i c a , but because of the small numbers present, analyses for Thysanoessa  s p i n i f e r a , T. longipes and T. r a s c h i i are reported as numbers 11 3 per 10 m of water f i l t e r e d . In three instances (Figs.118 -120 ) an exception to the above was made and E. p a c i f i c a was also reported i n numbers per 10 m^ . Examinations and measurements of the unmounted specimens were made using a L e i t z binocular microscope f i t t e d with an ocular scale c a l i b r a t e d against a stage micrometer. Specimens for morphological examination were dissected and mounted i n polyvinyl-lactophenol medium (Salmon, 1949) i n which a few drops of one per cent chlorasol black or l i g n i n pink had been previously mixed. These specimens were checked for the detailed, diagnostic characters appropriate to pa r t i c u -l a r developmental stages and species. 6 I I I . OCEANOGRAPHIC CONDITIONS 12 Indian Arm i s approximately 22 km long and 1 km wide. It extends due north from 48° 18' 10" N and 122° 56* 20" W, and i s one of the southern,mainland i n l e t s of B r i t i s h Columbia ( F i g . l ) . It i s bounded by precipitous mountains, and at i t s southern end opens into Burrard Inlet which in/turn connects with the S t r a i t of Georgia. A basin, with an average depth of 200 m, occupies the major part of the i n l e t . It shoals at the head of the i n l e t towards the delta of the Indian River, northwards from Station 2 (Fig. l a ) . A s i l l across the i n l e t ' s mouth i s about 26 m deep (Fig. l a , Station 23). This i s considerably shallower than the average s i l l - d e p t h of 106 m determined for other mainland i n l e t s of B r i t i s h Columbia (Pickard, 1961). Indian Arm i s included i n the group of i n l e t s with med-ium volumes of freshwater runoff (Pickard,1961). Freshwater enters from p r e c i p i t a t i o n , the Indian River, peripheral streams and from the discharge at the Buntzen power plant, situated mid-way along the i n l e t . Because i t s density i s lower than the saline waters, the freshwater forms a surface layer which flows southward towards the mouth. The volume of t h i s surface layer varies seasonally (Gilmartin, 1960,1962). The periods of freshwater runoff consist of a maximum i n the spring (approximately A p r i l to June), followed by minimum i n the mid-summer (approximately July to September), a secondary maximum i n the early winter (approximately October to December) and a secondary minimum i n the l a t e r winter (approximately January to March). During the seaward movement of the surface water, mixing occurs between i t and the more saline waters immediately be-low; the r e s u l t i s that the surface water becomes increasingly brack-is h (saline) from the head towards the mouth of the i n l e t , which i s 13 t y p i c a l of B r i t i s h Columbia i n l e t s (Pickard, 1955). The seaward movement of t h i s surface, brackish layer entrains more saline water from the underlying water of the i n l e t (Gilmartin, 1960). Considerations of continuity require that the saline water removed from the i n l e t i n the r e s u l t i n g outflow i s replaced by a compen-sating inflow at some subsurface depth of saline water from Burrard I n l e t . This inflow may be expected to be greater during the spring and early winter maxima of surface runoff than during the mid-summer and l a t e winter minima. Water from Burrard i n l e t also enters during the t i d a l c ycle. In addition occasional intrusions of larger amounts of water have been detected (Gilmartin, 1960, 1962; and McHardy, 1961). The surface, brackish water and the sub-surface water of higher s a l i n i t y i s e s s e n t i a l l y the two-layered system described for Indian Arm by Gilmartin (1960, 1962). DISTRIBUTION OF TEMPERATURE, SALINITY AND DENSITY (d"t) The maximum and minimum values of temperature, s a l i n i t y and oxygen recorded i n Indian Arm between January, 1960 and July-August, 1961, are summarized i n Table 1. The extremes of tempera-ture were observed i n surface waters and were 3.08 and 20.21°C. The lowest s a l i n i t y was 2.42°/ooat the surface, and the highest, 27.32°/coin deep water; oxygen ranged between 1.31 and 9.53 ml/1. Figure 2 i s a series of monthly, temperature-salinity (T-S) curves based on the mean values from the standard depths at the s i x stations, for the period from September, 1960, to J u l y -August, 1961. In general, temperature decreased and s a l i n i t y increased with increasing depth i n Indian Arm, excepting between December and March when temperatures were very low at the surface. This general s i t u a t i o n i s t y p i c a l of B r i t i s h Columbia i n l e t s 14 (Pickard, 1961). The temperature and s a l i n i t y values located towards the l e f t of the various curves (Fig. 2) include waters from the surface to approximately 5 m depth and as indicated by the broadness of the pattern, they varied appreciably i n tempera-ture and s a l i n i t y from month to month. These waters include the regions of maximum temperature and s a l i n i t y change ( i . e . , thermo-c l i n e and h a l o c l i n e ) , the nature of which i s c l o s e l y related to seasonal runoff and heat input i n the surface waters. The water from the intermediate depths, approximately 5 to 75 m, i s located i n the central part (dotted line s ) of the temperature-salinity diagram (Fig. 2). This has been named t r a n s i t i o n water and i s considered to r e s u l t from v e r t i c a l mixing of surface and deeper h i g h - s a l i n i t y waters. The depth range over which the t r a n s i t i o n water occurs has been somewhat a r b i t r a r i l y determined because of the d i f f i c u l t y of p r e c i s e l y demarcating i t s properties from those of surface and deep waters. For any given month, however, temperatures and s a l i n i t i e s f a l l between the values for surface and deep waters, but the chief distinguishing c h a r a c t e r i s t i c i s that the t o t a l range of temperature and s a l i n -i t y i n the t r a n s i t i o n water for the year i s subs t a n t i a l l y less than for surface waters, and greater than for deep water. The assigned range of temperature l i e s between approximately 7.5 and 13.5°C, and of s a l i n i t y between approximately 23.0 and 27.0 o/ Qo (Fig. 2). The compact group of temperature and s a l i n i t y values for the deep water (from about 7 5 to 200 m) suggests that t h i s water was r e l a t i v e l y stable i n i t s properties from September, 1960, to July-August, 1961. Temperatures ranged from approximately 7.5 to 8.0°C, and s a l i n i t i e s from approximately 26.8 to 27.320oo (Fig.2). The monthly and seasonal changes i n the temperature 15 and s a l i n i t y of surface waters are cl e a r from Fig.2. From June to October i n c l u s i v e the curves form a group i n which both tem-perature and s a l i n i t y vary widely. In June, high temperatures com-bined with low s a l i n i t i e s , the combination r e s u l t i n g from surface heating and from d i l u t i o n by large volumes of freshwater runoff. In contrast, the lower temperature and higher s a l i n i t y i n October r e f l e c t cooling of surface water and low runoff. Conditions between December and A p r i l (Fig.2) form-i.a~:s#cond ond group i n which s a l i n i t y i s the dominant v a r i a b l e . In t h i s group, r e l a t i v e l y isothermal conditions prevailed throughout the water column. The winter runoff of freshwater d i l u t e d the surface water to the low s a l i n i t i e s of December and February; these values were much lower than the s a l i n i t i e s for t r a n s i t i o n and deep waters. In January, March and A p r i l the r e l a t i v e l y high s a l i n i t i e s i n sur-face waters resulted from reduced runoff, but because of the small range of temperature i n the water column for t h i s period, s a l i n i t y remained the dominant v a r i a b l e . Figures 3 to 17 present monthly, temperature-salinity(T-S) scatter diagrams for Indian Arm from January, 1960 to July-August, 1961. Depth i n t e r v a l s , i n metres, indicate the appropriate ranges of depths for groups of intercepts (points) of temperature and s a l i n i t y . In the accompanying inserts (e.g.,Fig.3, inserts a and b) isotherms and isohalines show the d i s t r i b u t i o n s of the proper-t i e s for longitudinal sections of Indian Arm. The d i s t r i b u t i o n of density (o"t) i s shown i n longitudinal sections of the i n l e t i n Figs. 18, 19 and 20. In general, i t has been demonstrated (Tabata and Pickard, 1957) that variations i n o't c l o s e l y follow the variations i n s a l i n i t y i n B r i t i s h Columbia 16 i n l e t s . However, although s a l i n i t y i s usually more important than temperature i n determining s t a b i l i t y i n upper waters, at times temperature i s very important i n the s t a b i l i t y of Indian Arm waters, p a r t i c u l a r l y at intermediate depths and i n deeper water (Gilmartin, 1962). For convenience, the monthly T-S diagrams, and the d i s t r i b u t i o n s of temperature, s a l i n i t y and density (o't) are discussed for in t e r v a l s of three months. January, February and March, 1960 A comparison of T-S diagrams i n Figs. 3, 4 , and 5 demon-strate that i n Indian Arm, between January and March, 1960, there was a decrease i n temperature and an increase i n s a l i n i t y at depths between 10 and 200 m. The T-S diagram for January, 1960 (Fig. 3), suggests a three-layered system; surface, brackish water from 0 - 5 m; t r a n s i t i o n water i n which there i s a moderate range of temperature and small range of s a l i n i t y , from 10 - 50 m or more; and deep water with comparatively constant temperature and s a l i n i t y , from about 75 - 200 m. By March (Fig.5) there i s a surface, brackish water from 0 - 5 m, characterized by r e l a t i v e l y uniform temperature and a broad range of s a l i n i t y , and subsurface water from 10 - 200 m, characterized by small ranges of low tem-peratures (7.1 to 8.0QC) and high s a l i n i t i e s (26.9 to 27.3 °/oo). It appears that the properties of the waters at intermediate depths (approximately 10 - 50 m) have approached, and .partially merged with those of the deep waters (75 - 200 m) to give an appearance of a two-layered system. However, some indication of the three-layered system remains i n March i n that there i s a s l i g h t grouping and demarcation of water from 50 - 200 m from 1? that of 10 - 30 m. The longitudinal sections (Figs.3 - 5, inserts a and b; density, F i g . 18) indicate that the changes i n the oceanographic properties i n Indian Arm may have resulted from the entry and the subsequent movements of outside water. A comparison between January (Fig.3, i n s e r t a) and February (Fig.4,insert a) indicates that the surface and intermediate-depth waters cooled (7.5 and 7.9°C isotherms) i n February. By March, the temperature d i s t r i b u t i o n indicates that a large body of cold water (7.1 to 7.8°C) was present at the southern end at depths between 10 and 200 m (Fig.5, in s e r t a). The 7.1, 7.2 and 7.5°C isotherms, which were not present i n January and February,(or, as i n the case of the 7.5°C isotherm, was l i m i t e d to upper waters i n February) together with the lowered temperature of the bottom water at Sta-tions 6 and 9 (7.3°C as compared with 7.8 to 7.9°C) demonstrated the influence of t h i s water. Water of 27.0°/oo s a l i n i t y was not observed i n January (Fig.3,insert b). However, i n February s a l i n i t i e s of 27°/oo and higher were present from 60 or 70 m and i n March from 15 or 20 m downwards (Figs. 4 and 5, inserts b) and the s a l i n i t y of bottom water at Stations 6 and 9 increased from 26.97°/oo i n January to 27.28°/oo i n February and to 27.30°/°° i n March. Three isopycnals (lines of equal density) have been selected: 19.5 dt for the upper waters, 20.75 ot f o r water at intermediate depths ( t r a n s i t i o n a l water) and 21.0 o"t for the deep water. The isopycnal of 21.0 o*t lay between 150 and 170 m i n January; by February i t had decreased i n depth to between 50 and 60 m and by March to approximately 30 m (Fig.18, a, b, c) i n d i c a -t i n g a progressive and substantial increase i n the density of the 18 sub-surface waters. The isopycnal of 20.7 5 o't "accompanied" that of 21.0 o't, decreasing i n depth from 90 m i n January, to 30 m i n February, to 20 m i n March. During the three months the isopycnal of 19.5 o't remained at about 10 m, in d i c a t i n g that density i n the upper water was l i t t l e influenced by the large changes occurring i n the waters at intermediate and greater depths. The evidence derived from a decrease i n temperature and increases i n s a l i n i t y and density (o't) a l l point to one phenomenon, that cool, h i g h - s a l i n i t y water entered Indian Arm from outside.The only source of such comparatively highly saline water would be the S t r a i t of Georgia, v i a Burrard I n l e t . This water was of higher density than the resident water i t displaced, and therefore entered into the deep basin of Indian Arm and strongly influenced the oceanographic conditions i n February and e s p e c i a l l y i n March,1960. The entry of such water, i n r e a l i t y an in t r u s i o n of r e l a t i v e l y massive proportions, may have extended over several weeks. By March a r e l a t i v e uniformity of the temperature and s a l i n i t y had resulted between 10 and 200 m. The l a t t e r observation i s related to the transformation of the three-layered system of January into a system approaching two layers i n March. A p r i l , June and July, 1960 The T-S diagram for April,1960 (Fig.6),suggests that a t r a n s i t i o n water, at depths between 10 and 50 m, had begun to d i f f e r e n t i a t e from the low-temperature and h i g h - s a l i n i t y water which occupied depths between 10 and 200 m i n March, 1960. By June, t h i s t r a n s i t i o n water was strongly developed between 5 and 30 m, and by July, between 5 and 50 m (Figs. 7 and 8). Thus the three-layered system which had not been c l e a r l y evident i n the pre-ceding three months was strongly developed by June and Jul y . 19 Comparison of the T-S diagrams (Figs. 6 - 8 ) for A p r i l , June and July, 1960, demonstrates a progressive increase i n temperature and a decrease i n s a l i n i t y between 10 and 200 m. Seasonal warming of surface waters, freshwater runoff and t i d a l exchange, accompanied by v e r t i c a l and horizontal mixing were probably responsible for t h i s warming and d i l u t i o n of the cold, highly saline waters which intruded i n February and March, 1960. In surface waters, also,seasonal changes of temperature and s a l i n i t y were apparent between A p r i l and July, 1960. In A p r i l a maximum temperature of 8.3QC and a minimum s a l i n i t y of 10.0°/oowas recorded at the surface (Fig. 6); i n June these values were 13.7°C and 8.8P/fo (Fig.7), and i n July, 19.2°C and 18.0°/oo (Fig.8). In the temperature d i s t r i b u t i o n s for A p r i l , June and July, 1960 (Figs. 6, 7 and 8 - insert a) the progressive deepen-ing of the 7.5°C isotherm and the absence of water of 7.1 and 7.2°c suggests that the influence of the cold intruded water, p a r t i c u l a r l y apparent i n March, 1960, was decreasing. This was probably the r e s u l t of a seasonal increase i n heat input, as evident from the increase i n the temperatures of upper waters. The increase i n the temperature of bottom water at Stations 6 and 9, from a low of 7.3°C i n A p r i l to 7.5°C i n June and July (Figs. 6 - 8 , ins e r t a) may be i n d i c a t i v e of the v e r t i c a l extent of t h i s warming trend. The horizontal appearance of the isotherms of 7.5, 7 .6 and 7.8°C i n July, as compared with t h e i r slope i n A p r i l and June, suggests that up-inlet mixing between cool and warm waters was more or less completed and that oceanographic conditions i n the deeper waters were r e l a t i v e l y stable. 20 The deepening of the isohaline of 27.0°/oofrom 15 or 20 m i n March to 45 - 60 m i n A p r i l , to 7 5 ra i n June and to 90 m i n July, 1960 (Figs. 5 - 8, i n s e r t b), also suggest that mixing between the h i g h - s a l i n i t y , deep water which had previously intruded into the basin and l e s s - s a l i n e waters was occurring. The v e r t i c a l extent of t h i s mixing i s indicated i n the dilution.,.of > bottom waters at Station 6 and 9, where s a l i n i t y decreased from 27.30°/ooin March to 27.16Cyboby July, 1960. The gradual deepening of the isopycnal of 21.0°t from 30 m i n March to 80 - 90 m i n July, 1960, and of the isopycnal of 20.75°t from 20 m i n March to 60 - 75 m i n July (Fig. 18 c, d, e: F i g . 19 a), show there was a decrease i n the density of subsurface waters. This would ensue on downward mixing of low-s a l i n i t y , warmer water discussed above. The near surface isopyc-nal of 19.5^ also deepened, from 10 m i n March and A p r i l , to 20 - 30 m i n June, to 45 m i n July, 1960 (Fig. 18 c, d, e: F i g . 19 a). This s i g n i f i e d a decrease i n the density of the near-surface waters, which i s at t r i b u t a b l e to e f f e c t s of seasonal*warm-ing at and near the surface and the spring and early summer runoff of freshwater. September, October and December, 1960 The T-S diagram for September, 1960 (Fig.9), shows that the three-layered system of surface water, t r a n s i t i o n water (between 5 and 50 m) and r e l a t i v e l y cold, h i g h - s a l i n i t y water between 7 5 and 200 m persisted but weakened. I t continued during October (Fig.10), but there was a s l i g h t decrease i n temperature and an appreciable increase i n s a l i n i t y at depths between 5 andiS'O m; 21 t h i s , coupled with the increase i n temperature and s a l i n i t y at 75 m extended the range of depth of t r a n s i t i o n water to between 5 and 75 m on the T-S diagram. By December, the temperatures between 5 and 75m and s a l i n i t i e s between 10 and 75 m indicated a substantial decrease i n temperature and a further increase i n s a l i n i t y (Fig. 11); and with these changes, the t r a n s i t i o n water became continuous i n s a l i n i t y with the deeper water. Thus the d i s t i n c t , three-layered system established i n June and main-tained u n t i l October, has become less well defined by December, 1960. In surface water seasonal cooling and fluctuations i n d i l u t i o n from freshwater runoff are apparent (Figs. 9, 10 and 11). The maximum temperature and minimum s a l i n i t y ranged from 15.2°C and 17°/ooin September, to 14.0°C and 1 9 % o i n October, to 10.4°C and 7*/6o i n December. Clearly the e f f e c t s of runoff on the surface water, increased sharply i n December. The d i s t r i b u t i o n s of temperature (Figs. 9, 10 and 11 -in s e r t a) show that, at depths between 5 and 50 m, temperatures decreased from 13.0 - 10.0°C i n September, to 12.0 - 10°C i n October, to 10.0 - 9,0°C i n December. In deeper waters, however, temperatures increased as shown by the deepening of the 8.0°C isotherm from 75 m i n September to 90 m i n October to 120 m i n December. In bottom waters there was also a progressive increase of temperature, from 7.55°C i n September to 7.6°C i n October to 7.71°C i n December (Figs. 9, 10 and 11 - ins e r t a). For s a l i n i t y , the 26.75°/6o isohaline became shallower moving from 75 m i n September to between 30 and 60 ra i n October and then to between 20 and 30 m i n December, 1960 (Figs. 9, 10 and 11 - i n s e r t b ). This i s i n d i c a t i v e of an increase i n s a l i n i t y 22 between 10 and 75 m during October and December. The downward slope i n October of the isohalines of 26.0, 26.5, 26.75 and 27.0°/6o from Station 23 towards Station 2, indicate that, for a given depth, s a l i n i t i e s were decreasing towards the head of the i n l e t . By December, however, the positions of these isohalines i n d i c a -ted that, for a given depth, s a l i n i t i e s were si m i l a r throughout the i n l e t . The change of depth of the isopycnal of 20.75 ^ t from 75m i n September and October to 30 - 45 m i n December (Fig. 19 b, c, d) demonstrates an increase i n density for intermediate-depth waters; t h i s i s also indicated by the increased separation of isopycnals of 20.75 o" tand 21.0 °"t- which were about 15. m apart from February to October (Fig. 18 a-e and 19 b , c ) , but had increased to 45 - 70 m apart by December, 1960 (Fig. 19 d). Towards the end of 1960 the isopycnal of 19.5 °t became shallower, from 10 - 30 m i n September to 5 - 10 m i n October and December (Fig. 19 b, c, d), in d i c a t i n g an increase i n density of waters between 5 and 30 m. The sustained p o s i t i o n of the isopyncal of 21.0 (at 90 - 100 m) suggested that density was s i m i l a r i n the deeper waters from September through December (Fig. 19 b, c, d). The general decrease i n temperature at depths between 5 and 50 m i n October and 5 and 7 5 m i n December, 1960 (Figs,10 and 11), could be attributed i n part to the seasonal cooling of surface water and subsequent v e r t i c a l mixing with the underlying water. However, the progressive increase i n s a l i n i t y of water between 10 and 75 m during these months, (as demonstrated by the shoaling of the 26.7 5°/oo isohaline) i s believed to have resulted from an i n t r u s i o n of r e l a t i v e l y h i g h - s a l i n i t y water from outside of Indian Arm. The downward slope i n October of the isohalines (Fig. 10 insert b), from Station 23 towards Station 2, also indicate t h i s as does the increase i n density i n intermediate-depths i n December (Fig. 19 d). It seems probable that the density of the outside water was similar to the Indian Arm water at the depths of these isohalines. I f so, the intruded water flowed along them, but by December,(Fig. 11, i n s e r t b), t h e i r more or less horizontal p o s i t i o n indicates that r e l a t i v e l y stable conditions were again present i n the i n l e t . This water may have been colder than the resident water, which would help to account, along with seasonal cooling, for the cooling between 5 and 75 m from October to December. Such an intrusion at intermediate-depth may also be implicated i n the downward displacement of the 8.0°C isotherm from 75 m i n September to 90 m i n October to 120 m i n December. January, February and March 1961 The T-S diagrams for January, February and March,1961 (Figs. 12, 13 and 14), suggest r e l a t i v e l y stable conditions. This was unlike the s i t u a t i o n reported for the same period i n 1960 (Figs. 3, 4 and 5) when there was a "bunching" of the temperature-s a l i n i t y points for depths between 10 and 200 m, p a r t i c u l a r l y i n March. In the f i r s t three months of 1961, much of the t r a n s i t i o n water, located between 10 and 50 m, was weakly demarcated from the deep water i n the T-S diagrams but even so the water column appears as a three-layered system. The low temperatures of December persisted i n the surface waters (Figs. 12, 13 and 14); and an abrupt decrease i n the s a l i n i t y i n February probably r e f l e c t s an increase i n p r e c i p i t a t i o n and freshwater runoff(Fig.13). 24 The d i s t r i b u t i o n of temperature for January (Figs. 12, ins e r t a) shows a subsurface tongue of r e l a t i v e l y warm water, delineated by the 8.5°C isotherm. This tongue occurred at i n t e r -mediate depths and extended down-inlet from Station 2. It prob-ably was a continuation of similar tongues of warmer water (delineated by 9.0 and 10.0°C isotherms) which were present i n December, 1960, possibly as a remnant of warm water of the previous summer. By February and March (Figs. 13 and 14 - inse r t a) the 8.5°C tongue was r e s t r i c t e d between Stations 2 and 6. In March, 1961, other tongues, delineated by the isotherms of 7.75, 8.0 and 8.25°C, extended up-inlet. They are in d i c a t i v e of a decrease i n temperature at depths between 10 and 60 m (Fig.14, ins e r t 3). Between December, 1960, and January, 1961, the isohalines of 26.75 and 27.0°/bo deepened and the bottom water of 27.15°/oo disappeared. These changes indicate that the s a l i n i t y decreased between approximately 15 and 200 m (Figs. 11 and 12 - inse r t b), probably because of extensive mixing between the l e s s - s a l i n e resident waters and the waters which intruded i n December. A gradual deepening of the isohaline for 26.75°/x> from approximately 60 m i n January to about 7 5 m i n March, and of the isohaline of 27.0°/oo from 130 to 180 m i n January to 180 m i n March (Figs. 12, 13 and 14 - insert b) indicates a continuous decrease i n s a l i n i t y during the period. The deepening of the isopycnal of 21.0 °~t, from between 90 and 100 m i n January, to 90 - 120 m i n February, to 150 m i n March, 1961 (Figs. 19 e and 20 a, b), continues the trend which began i n A p r i l , 1960. In January, February and March, 1961 the isopycnal of 20.7 5 t returned to a depth range ( 60 to 75 m) similar to that i n October, 1960, thus in d i c a t i n g that the influence on density of the intrusion of December, 1960 (Figs. 19, c, d, e and 20 a, b) was s h o r t - l i v e d . In surface waters, the isopycnal of 19.5 ^ t remained between 5 and 10 m, indicating that the density was r e l a t i v e l y unchanged over the three months (Figs. 19 e and 20 a, b). Oceanographic conditions between 10 and 200 m appeared to be r e l a t i v e l y stable i n January, February and March, 1961, with the r e s u l t that the water column approximated a three-layered system. This was unlike the s i t u a t i o n i n the same period i n 1960. The influence of the in t r u s i o n of December, 1960, appeared to be s h o r t - l i v e d as shown by the return i n January of the isohalines of 26.75 and 27.0°/bo and the isopycnal of 20.75c3t to depths s i m i l a r to those p r i o r to the in t r u s i o n . The decrease i n temperature of waters between 10 and 60 m i n March, 1961, as shown by the isotherms of 7.75, 8,0 and 8,25 extending up-inlet, suggest the possible entry into Indian Arm of cool waters from outside. A p r i l , June and July-August, 1961 The T-S diagram for A p r i l , 1961 (Fig.15), shows con-tinuance of the i n d i s t i n c t three-layered system of the preceding three months. However, during June and July-August (Figs. 16 and 17), the t r a n s i t i o n water, between 5 and 50 m was strongly developed and s i m i l a r to the s i t u a t i o n i n June and July, I960. Maximal temperatures i n surface waters increased from 14.0.C i n A p r i l to 19.8°C i n July-August. The decrease of surface s a l i n i t y from 14.0?/ooin A p r i l to 7.5°/ooin June i s related to increasing 26 freshwater runoff, and the increased s a l i n i t y i n July-August to a decrease i n t h i s runoff. In the d i s t r i b u t i o n of temperature for A p r i l , 1961 (Fig. 15 - ins e r t a), the warm-water tongue (8.5°C isotherm), apparent i n previous months, i s seen to p e r s i s t only at depths between 60 and 90 m at Stations 2 and 6. In June and July-August, there was a seasonal increase i n the temperature of waters between 0 and 50 m (Figs. 16 and 17 - insert a); the 8.5°C tongue which had progressively retreated towards the head of the i n l e t from January to A p r i l , 1961, has dissipated. The abrupt, upward slope of the 8.0°C isotherm from 150 m at Station 9 to 90 m at Station 2 i n June, 1961, may be related to the concurrent changes i n the d i s t r i b u t i o n of s a l i n i t y at these depths. The 27°/6o isohaline i s observed to s h i f t surfaceward from 180 m i n March, to 160 - 180 m i n A p r i l , to 90 - 120 m i n June (Figs. 14, 15 and 16 - insert b) i n d i c a t i n g an increase i n the s a l i n i t y of the deeper waters. Concurrently, the s a l i n i t y of the bottom waters at Stations 6 and 9 increased from 27.0°/6o i n March to 27.18*^00 i n June, 1961. In July-August, 1961, water of 27.0°/oo or greater s a l i n i t y deepened (Figs. 16 and 17 - ins e r t b), and i t s extent was reduced to a tongue l y i n g at 120 - 150 m, between stations 2 and 9. Thus there was an o v e r a l l decrease i n the s a l i n i t y of the deeper waters. The isopycnal of 21.0 °~t became shallower, from 150 m i n March, to 135 m i n A p r i l , to 90 - 115 m i n June, 1961 (Fig. 20 b, c, d), in d i c a t i n g a progressive increase i n the density of deep waters, corresponding with the increase i n s a l i n i t y for the same period. However, i n July-August, 1961, water of 21.0 °t became r e s t r i c t e d to a tongue between 135 and 180 m (Fig.20 e), t h i s decrease i n density also corresponding with the decrease i n s a l i n i t y discussed above. The isopycnal of 19.5 ^ t deepened, from 10 m i n A p r i l , to 45 m i n June, to 45 - 60 m i n July-August, 1961 (Fig. 20 c, d, e). As i n the comparative period i n 1960, t h i s decrease of density i n the upper waters r e f l e c t s seasonal warming and the downward mixing of runoff. There was a noticeable increase i n the s a l i n i t y and i n the density of deeper waters (100 - 200 m) from A p r i l to June, 1961. The slopes of the isohalines did not suggest an inflow of h i g h - s a l i n i t y water into the i n l e t during t h i s period, but such increases i n s a l i n i t y and density usually denote the entry of water from outside. The abrupt upward slope of the 8.0°C isotherm towards the head of the i n l e t i n June suggests changes i n the basin of the i n l e t , perhaps as a r e s u l t of water intrud-ing from outside. There was a decrease i n the s a l i n i t y and density of the deeper waters from June to July-August, 1961, which suggests that the influence of the intruded water was lessening, possibly because of mixing with resident waters. From the above i t seems probable that there was an intrusion of outside waters at some time between sampling i n A p r i l and early June, 1961, which influenced the deeper waters i n Indian Arm, and that the e f f e c t s of such were lessening by July-August, 1961. 28 DISCUSSION OF TEMPERATURE, SALINITY AND DENSITY The annual temperature-salinity (T-S) diagram for the period from September, 1960, to July-August, 1961 (Fig. 2), and the maximum and minimum temperatures, s a l i n i t i e s and oxygen values for the period from January, 1960, to July-August, 1961 (Table 1), demonstrate a wide range of oceanographic conditions i n Indian Arm. During the period of the present study there were seasonal fluctuations i n oceanographic conditions at depths between the surface and approximately 50 m (Figs. 2 - 20; inserts a and b). In general, temperatures decreased and s a l i n i t i e s and density increased during January to A p r i l , 1960, and October, 1960 to A p r i l , 1961; these months are associated with cold a i r temperatures and with low runoff, as most p r e c i p i t a t i o n i s i n the form of snow. Increased runoff l e d to lowered s a l i n i t i e s at the surface i n December, 1960, and February, 1961, r e s u l t i n g from heavy r a i n . The e f f e c t s of the seasonal,climatic fluctua-tions on the increase of s a l i n i t y and density between 10 and 75 m during October to December, I960, were not c l e a r l y d i s t i n g u i s h -able from the similar influence on these properties of the i n t r u -sion of outside waters i n these months. In general, at depths between the surface and approxi-mately 50 m, temperatures increased and s a l i n i t i e s and density decreased during the warmer months of June to September, 1960, and June to July-August, 1961. During these months, and i n par-t i c u l a r from A p r i l to June, snow melts and the freshwater runoff i s heavy. 29 • From the two preceding paragraphs, i t i s apparent that there are broad, seasonal relationships between temperature, freshwater runoff, s a l i n i t y and density i n the upper waters of Indian Arm. The oceanographic properties of the deep waters were r e l a t i v e l y stable during non-intrusion periods ("normal" periods) and were not subject to the seasonal fluctuations of the upper waters. Following on intrusions, however, the temperature decreased and s a l i n i t y and density increased at depths between 10 and 200 m i n February and March, 1960 (Figs. 4, 5 and 18 b,c) and temperature was influenced and s a l i n i t y and density increased between 100 and 200 m i n A p r i l to June, 1961 (Figs. 15, 16 and 20 c, d). Subsequent to the intrusion of February - March, there was a general decrease i n s a l i n i t y (Figs. 6 - 1 7 , ins e r t b) and density (Figs. 18 - 20) i n the deep waters from A p r i l , 1960, to July-August, 1961. These trends were i n d i c a t i v e of the return of oceanographic conditions to the "normal" s i t u a t i o n for Indian Arm, but they were interrupted by the increase i n the s a l i n i t y and density i n deeper waters r e s u l t i n g from the intrusion between A p r i l and June, 1961 (Figs. 15, 16 and 20 c, d). Gilmartin (1960, 1962) reported an intrusion into Indian Arm between January and March, 1957, when the resident waters apparently were displaced and flushed. In the present study, the intrusions consisted of a massive one i n February - March, 1960, and two smaller ones between October and December, 1960, and A p r i l and June, 1961. The immediate source of the intruding water must have been Burrard Inlet, an* extension of the S t r a i t of Georgia. The large i n t r u s i o n i n February and March, 1960, was sim i l a r to that which occurred i n 1957 (McHardy, 1961) and i t 30 influenced temperature, s a l i n i t y and density at depths between 10 and 200 m throughout Indian Arm (Fig. 4, 5 and 18 b, c ) . These intrusions probably r e s u l t when water immediately outside ,Indian Arm and above i t s s i l l depth (26m) i s , or becomes, denser than the water below t h i s depth within the i n l e t . A density i n s t a b i l i t y would a r i s e and therefore water would flow into the i n l e t and, i f the density were high enough, into the deep basin. The r e s u l t would be an upward displacement of the resident waters which would flow out of the i n l e t at surface and sub-surface depths. Following t h i s , the intruded water would grad-u a l l y mix with the remaining less dense, resident waters. T i d a l Slow into and out of the i n l e t would probably a s s i s t i n t h i s mixing. An in d i c a t i o n of the size and influence of the i n t r u s -ion of February and March, 1960, i s that i t was some eleven months ( A p r i l , 1960, to March, 1961) before the isopycnals of 20.7 5 o't and 21.0 o't returned to t h e i r pre-intrusion l e v e l s of January, 1960 (Figs. 18, 19 and 20). The small intrusion between October and December, 1960, influenced s a l i n i t y (and thereby density) but probably not tem-perature, at depths between 10 and 75 m (Figs. 10, 11 and 19 c,d). The in t r u s i o n between A p r i l and June, 1961, influenced s a l i n i t y , density and perhaps temperature at depths between 100 and 200 m (Figs. 15, 16 and 20 c, d). The e f f e c t s of these intrusions were l i m i t e d not only i n extent but i n duration. Possibly they resulted from small amounts of outside water crossing the s i l l , rather than i n a large replacement, as appeared to be the case i n February-March, 1960. As shown by the s a l i n i t y values for December, 1960, and June, 1961 (Figs. 11 and 16), the d i l u t i o n 31 of surface waters by freshwater was high, i n d i c a t i n g an increased outflow from the i n l e t . Therefore, small intrusions may have resulted from r e l a t i v e l y h i g h - s a l i n i t y water from outside replac-ing the volume of water entrained from the i n l e t by the surface outflow (see p.13 ). In the present study, i t i s convenient to regard the water column i n Indian Arm as being b a s i c a l l y a three-layered system. At depths between the surface and about 5m i s a layer i n which wide fluctuations of temperature and s a l i n i t y occur. Between about 10 and 50 m i s the t r a n s i t i o n water i n which the temperature and s a l i n i t y changes are intermediate between those at the surface and the small changes which occur i n the deep waters. Lastly there i s the deep water between about 75 and 200 m, where r e l a t i v e l y low temperatures and high s a l i n i t i e s prevailed and where fluctuations were s l i g h t . Close examination indicates that although the water column was b a s i c a l l y three-layered the amount of t r a n s i t i o n water at intermediate depths fluctuated. The T-S diagrams for summer and autumn (between June and October) indicate the pres-ence of surface water, t r a n s i t i o n water (with a r e l a t i v e l y wide range of temperature and s a l i n i t y for t h i s water), and deep water (Figs. 7 - 10, 16 and 17). For December to A p r i l , however, the t r a n s i t i o n water was characterized by small ranges i n tempera-ture and s a l i n i t y and i t s properties approached more nearly to those of the deep water (Figs. 3 - 6 , 11 - 15). Thus i n Indian Arm the waters fluctuated between being d i s t i n c t l y three-layered during the summer and autumn and less d i s t i n c t l y three-layered 32 i n the winter and spring. This interpretation d i f f e r s from the two-layered system of surface, brackish water and subsurface, high s a l i n i t y water discussed for Indian Arm by Gilmartin (1960). The approach to a two-layered system, with l i t t l e or no t r a n s i t i o n water between the surface and deep waters, was found, i n p a r t i c u l a r , following intrusions of water o r i g i n a t i n g outside of Indian Arm. The r e l a t i v e l y uniform temperatures and s a l i n i t i e s (and the approach to a two-layered system) between 10 and 200 m i n February and March, 1960, have been attributed to such an in t r u s i o n . The intruded water was of higher s a l i n i t y and lower temperature than any water i n the i n l e t (that i s , during January, 1960). The e f f e c t as i t entered and mixed with the resident water was to increase the s a l i n i t y and decrease the temperature between 10 and 200 m. In the T-S diagrams for these months, a merging of the t r a n s i t i o n water at intermediate depths and deep water occurred with a two-layered system (consisting of surface, brackish water and subsurface, high s a l i n i t y water) as a conse-quence. This i s p a r t i c u l a r l y evident i n the T-S diagram for March, 1960 (Fig. 5). The continuing presence of t r a n s i t i o n water interconnect-ing the surface and deep waters i n January, February and March, 1961 (Figs. 12 - 14) i s i n contrast to the condition which developed during these months i n 1960. It i s probably a t t r i b u t -able to the absence of detectable intrusions of outside water during t h i s period. 33 An intrusion of r e l a t i v e l y h i g h - s a l i n i t y water which entered Indian Arm at intermediate depths between October and December, 1960, increased the s a l i n i t i e s between 10 and 75 m. The r e s u l t i s most apparent i n the T-S diagram for December (Fig. 11), i n which the s a l i n i t y values for water from these i n t e r -mediate-depths again tend to merge with those for deep water, again producing almost uniform s a l i n i t i e s for depths between 10 and 200 m. However, on the basis of temperature differences between the water at intermediate depths (9.0 to 10.2°C) and deep water (7.7 to 8.5°C) i t i s possible to d i f f e r e n t i a t e the t r a n s i t i o n water, even though i t s s a l i n i t y i s s i m i l a r to that of deep water. Transition water at intermediate depths was becoming d i f f e r e n t i a t e d again i n A p r i l and was well developed by June, 1961 (Fig. 15 and 16). In these months outside water again intruded into Indian Arm, but i t influenced the water of the deep basin between 100 and 200 ra. Possibly because of t h i s , the seasonal formation of t r a n s i t i o n water at the intermediate depths was not precluded. The regions of maximum temperature and s a l i n i t y change ( i . e . , thermocline and halocline) were present i n the waters from the surface to approximately 5 - 10 m i n depth. (Fig. 2). In general, the s a l i n i t y gradient i n these waters was maximal (a range of 1.5 - 3.2 °/oo/m, from 0 to 5 m ) i n the periods of increased runoff of freshwater, during A p r i l to June, 1961, and December, 1960, to February, 1961, and was minimal (a range of 0.7 - 1.0 °/oo/m, from 0 to 5 m ) i n ther periods of low runoff, 34 during September and October, 1960, and March and July-August, 1961. The temperature gradient i n these waters was maximal ( a range of 1.0 - 1.2 C°/m ) during June and July-August, 1961, i n periods of warming, and was minimal (a range of 0.08 - 0.6 C°/m ) from September, 1960,to A p r i l , 1961, i n periods of cooling. The influence of the thermocline and hal o c l i n e on the v e r t i c a l d i s -t r i b u t i o n and migration of zooplankton i s of considerable import-ance i n the following studies of euphausiids i n Indian Arm and i n the laboratory, 35 • IV. TEMPERATURE, SALINITY AND THE OCCURRENCES OF EUPHAUSIIDS The changing conditions of temperature and s a l i n i t y i n Indian Arm, i n whatever manner they originate, are i n d i c a t i v e of a variable environment encountered by plankton i n the i n l e t . In p a r t i c u l a r , intrusions of outside waters, i n that they induce r e l a t i v e l y large and rapid changes, may be expected to influence occurrences, d i s t r i b u t i o n and abundance of species i n the i n l e t . In addition, seasonal fluctuations i n the temperature and s a l i n -i t y of the surface water, and the formation of t r a n s i t i o n water at intermediate depths may be important considerations i n the v e r t i c a l d i s t r i b u t i o n of the zooplankton species. In recent years, a technique has been developed (Pickford, 1946, 1952) i n which occurrences of plankton are presented i n a diagram i n d i r e c t r e l a t i o n to the temperature and s a l i n i t y of the water at the time and place at which the organisms were c o l l e c t e d . These c o r r e l a t i o n diagrams have been further developed by Bary; he refers to them as temperature-salinity-plankton (T-S-P) diagrams (Bary, 1959). The diagrams r e l a t e species to temperature and s a l i n i t y condition per se, and to "bodies" of water (Bary, 1963 a, c and d, 1964) as these are delineated by t h e i r temperatures and s a l i n i t i e s (Helland-Hansen, 1916) (see Sverdrupet a l , 1942). In the present study, concurrent data on temperature and s a l i n i t y and the occurrences of euphausiids in Indian Arm are presented i n monthly and annual T-S-P diagrams. These have been used to indicate the reactions to t h e i r environment, and to 36 changes i n i t , of the adults of four species (Euphausia  p a c i f i c a , Thyanoessa s p i n i f e r a , Thysanoessa longipes and Thysanoessa r a s c h i i ) , and the developmental stages of E. p a c i f i c a , by means of changes i n occurrences and fluctuations i n abundance of the species and stages. The "annual" T-S-P diagrams (Figs. 21 - 27) delineate gross relationships of the species and developmental stages, based on presence or absence, to t o t a l ranges of temperature and s a l i n i t y , over the period from September, 1960, to July-August, 1961. The s o l i d or dotted l i n e enclosing a number of points indicates the range of temperature and s a l i n i t y over which a p a r t i c u l a r species or developmental stage was coll e c t e d ; the points outside of these areas represent conditions i n which no specimens were c o l l e c t e d . The geographical d i s t r i b u t i o n s for the corresponding period are presented i n longitudinal sections of Indian Arm (Figs. 28 and 29). The hatched areas i n these reproduce i n another way the enclosed areas i n the appropriate T-S-P diagrams. Monthly T-S-P diagrams are presented for adult?specimens of the four species from January, 1960, to July-August, 1961 (Figs. 30 - 44, 83 - 97, 99 - 111 and 113 - 117), and for the developmental stages of E. p a c i f i c a from September, 1960, to July-August, 1961 (Figs. 4 6 - 8 2 ) . In contrast to the "annual" T-S-P diagrams, these concern short periods. The reactions of organisms to short-term changes and seasonal fluctuations i n temperature and s a l i n i t y , become apparent by comparing a series of such diagrams. Depth i n t e r v a l s , in metres, indicate the v e r t i c a l range from which groups of temperature-salinity points and organisms were obtained at the s i x stations i n Indian Arm. The occurrences of euphausiids are presented as the numbers co l l e c t e d per unit volume of seawater f i l t e r e d (Tables 2 and 3). The blocked i n and open c i r c l e s indicate the presence of speci-mens during night and day respectively; half-blocked c i r c l e s indicate that specimens were c o l l e c t e d during both night and day. Relative abundance i s indicated by the diameter of the c i r c l e ; the small points represent temperatures and s a l i n i t i e s at which specimens were not c o l l e c t e d . Inserts on some diagrams show occurrences and abundance i n deeper waters on an enlarged scale. The monthly occurrences and r e l a t i v e abundance of species are also shown i n longitudinal sections of Indian Arm (Figs. 45, 46 - 82, 98 and 112 - 117). These provide geograph-i c a l o rientation for the occurrences as presented i n the corres-ponding T-S-P diagrams. Euphausia p a c i f i c a Adults From September, 1960, to July-August, 1961, Euphausia  p a c i f i c a occurred, as shown by the several enclosed areas i n F i g . 21 over temperatures ranging from 5.3 to 13.8°C and s a l i n -i t i e s from 7.0 to 27.15°/oo. The largest area represents the temperature-salinity conditions of subsurface waters (7.6 to 13.8°C; 23.5 to 27.15 °/oo) i n which specimens were co l l e c t e d i n maximum abundance. The several small areas (over the ranges of 5.3 to 7.5°C and 7.0 to 21.0 °/oo) represent the conditions 38. i n surface water i n which small numbers of specimens were c o l l e c t e d i n December, 1960, and January, February and March, 1961. It i s also apparent that there were associated conditions of temperature and s a l i n i t y from which specimens were not co l l e c t e d . Geographically E. p a c i f i c (Fig. 28 a) was c o l l e c t e d during the 12 months at a l l stations and i n surface, i n t e r -mediate-depth and deeper waters. Specimens were noticeably absent below 120 m at Station 9 and i n bottom waters at Station 6. Such absence from the deepest waters i s an important, con-s i s t e n t feature of the occurrences of E. p a c i f i c a . Specimens were c o l l e c t e d at night i n surface waters from January to A p r i l , 1960 (Figs. 30 - 33), and from December, 1960, to March, 1961 (Figs. 38 - 41). The numbers were low, 0.1 to 7.8 animals/m^, and coincided with and may be related to, the seasonal cooling of surface waters i n Indian Arm. Temperatures ranged from 5.3 to 8.5°C, approaching that of subsurface waters (7.2 to 9.8°C). The small c o l l e c t i o n at the surface i n February, 1961 (Fig. 40), was made i n water of 5.3°C and 7.0 °/oo, values which were minimal for c o l l e c t i o n s during the entire sampling programme (Table 4). Of the surface c o l l e c t i o n s , specimens were most abundant (4.1 and 7.8/ra^) i n March, 1961 (Fig.41) when the water was cool (5.5 to 7.8°C) and of moderately high s a l i n i t y (18.9 to 22.4 °/oo). Specimens were not co l l e c t e d i n surface waters.from June to October, 1960 (Figs. 34 - 37), or from A p r i l to July-August, 1961 (Figs. 42 - 44). The f a i l u r e to c o l l e c t specimens i n the 39 r e l a t i v e l y cool, surface waters (9.0 to 10.1°C) i n A p r i l , 1961 (Fig.42), may have resulted from the absence of plankton tows during the night i n t h i s month. Except for April,1961, the temperature at the surface ranged from 12.0 to 20.0°C for the months during which no specimens were c o l l e c t e d . Specimens were c o l l e c t e d i n subsurface waters thoughout the sampling period. Numbers were often high, up to 37.9/m3. Euphausia p a c i f i c a demonstrated a d i e l v e r t i c a l migration; i n general, occurrences v e r t i c a l l y appear to be defined into night (0 to 60 m) and day (30 to 180 m) l e v e l s , with overlap at i n t e r -mediate depths (Fig. 45 a-o). During January, February and March, 1960 (Figs. 30, 31 and 32), there was a progressive decrease i n temperature and increase i n s a l i n i t y of the subsurface waters, but despite these changes, E. p a c i f i c a continued to be present. Thus, i n January (Fig. 31), specimens were c o l l e c t e d at temperatures of 8.1 to 9.0°C and s a l i n i t i e s of 26.4 to 26.9 °/oo and by March (Fig.32) i n temperatures of 7.2 to 7.8°C and s a l i n i t i e s of 27.0 to 27.3 °/oo (but not at depths of 150 and 180 m). From the geographical occurrences of specimens (Fig.45 a, b, c) i t i s apparent that from January to March, 1960, there was a general decrease in=rthe numbers present. This amounted to 19%. By A p r i l , 1960 (Figs. 33 and 45 d), numbers /m^  were the lowest recorded. A comparison of the abundances at Station 12, 9 and 6 for January and A p r i l indicates t h i s decrease approximated 73% ; only at Station 2, (Fig. 1) near the head of the i n l e t was the abundance maintained. 40 During A p r i l , June and July, 1960 (Figs. 33, 34 and 35), temperature increased and s a l i n i t y decreased i n waters at the surface and at intermediate depths. The occurrences of speci-mens at 30 and 60 m, however, indicate that E. p a c i f i c accommo-dated to these changes. For example, specimens were c o l l e c t e d at 30 m i n water with temperatures and s a l i n i t i e s of about 7.9°C and 26.4 °/oo i n A p r i l (Fig. 33), 9.5 and 25.0 °/oo i n June (Fig. 34) and 11.0°C and 24.8 °/oo i n July (Fig. 35). Specimens were not c o l l e c t e d at 150 and 180 m except once i n June. The geographical occurrences indicate that i n A p r i l , June and July,nl960 (Figs. 45 d, e, f ) , specimens were c o l l e c t e d at the same depths (30, 60, 90 and 120 m) as i n previous months. They were absent from the deeper waters, excepting the small c o l l e c t i o n i n June of 0.1 specimens/m3, made at 180 m at Station 9. There was a four-fold increase i n the ove r a l l abundance of specimens from A p r i l to July . In June (Fig. 45e) there was an increase i n the r e l a t i v e abundance at 30 and 60 ra at Stations 15, 12 and 9, towards the mouth of the i n l e t , and a decrease at Station 2, towards i t s head. By July (Fig. 45 f) specimens were r e l a t i v e l y abundant at 30, 60 and 90 m, between Stations 15 and 2. The T-S-P diagrams for September, October and December, 1960 (Figs. 36, 37 and 38) show that during the process i n which t r a n s i t i o n water "merged" with the deep waters (p. 33), specimens at 30 and 60 m remained at these depths despite the ensuing decrease i n temperature and the increase i n s a l i n i t y . For example, at 30 m specimens were c o l l e c t e d at temperatures and s a l i n i t i e s 41 of about 11.5°C and 25.9 °/oo i n September (Fig. 36), 11.0°C and 26.5 °/oo i n October (Fig. 37), and 9.7°C and 26.8 °/oo i n December (Fig. 38), 1960. The geographic p r o f i l e s i l l u s t r a t e that during September, October and December, 1960 (Figs. 45 g, h, i ) there were d i s -s i m i l a r i t i e s i n the d i s t r i b u t i o n and abundance of specimens. In September, specimens were most abundant and evenly d i s t r i b u t e d at 30, 60 and 90 m from Station 15 to 2, but except for one c o l l e c t i o n at 120 m, at Station 9, they were absent below 90 m. In October, there was a decrease i n the r e l a t i v e abundance at Stations 15, 12 and 9. The population appeared to be concen-trated towards the head of the i n l e t at Stations 6 and 2, and at greater depths (90 and 120 m) than usual; no specimens were co l l e c t e d below 120 m. By December, specimens were concentra-ted at Station 2, and i n the deeper waters at Stations 6 and 9; the c o l l e c t i o n s at 90 m and i n bottom water at Station 2 rep-resented the maximum abundance of specimens, up to 37.9/m^; recorded during the sampling programme. Except for the small c o l l e c t i o n (0.3 animals/m^) at 180 m, specimens were not co l l e c t e d below 120 m i n December. From September to December, however, there was an increase i n the r e l a t i v e abundance of specimens at 120 m, and i n December, the numbers c o l l e c t e d at that depth were considerably larger than i n any of the preced-ing months. Thus the occurrences of B. p a c i f i c a moved towards the head and into the deeper waters of the i n l e t during the period from October to December, 1960. 42 Small changes i n subsurface waters i n the d i s t r i b u t i o n of temperature and s a l i n i t y , and s i g n i f i c a n t changes i n the occurrences of specimens took place between December, 1960, and January, 1961 (Figs. 38 and 39). The temperature between 30 and 180 m ranged from 7.6 to 9.7°C i n December and from 7.7 to 8.7°C i n January; s a l i n i t y ranged from 26.7 to 27.15 °/oo i n December, to 26.3 to 27.0 °/oo i n January. Unlike the s i t u a -t i o n i n December when E. p a c i f i c a occurred towards the head of the i n l e t and i n the deeper waters there (Fig. 45 i ) , i n January specimens were di s t r i b u t e d more evenly between Stations 15 and 2 and were absent below 90 m (Fig. 45 j ) . The d i s t r i b u t i o n i n January, 1961, thus c l o s e l y resembled that during September, 1960. In the T-S-P diagrams for January to A p r i l , 1961 (Figs. 39 - 42), occurrences of E. p a c i f i c a are shown for a period when r e l a t i v e l y stable conditions of temperature (7.7 to 8.7°C) and s a l i n i t y (26.0 - 27.0 °/oo) prevailed i n waters between 30 and 180 m. Geographically, from January to A p r i l , 1961 (Fig. 45 j , k, 1, m) specimens were more or less evenly d i s t r i b u t e d at depths less than 90 to 120 m (the occurrences for A p r i l were li m i t e d to day c o l l e c t i o n s ) , and i n general, for the standard sampling depths (30, 60 and 90 m), the abundance was similar from month to month. These results d i f f e r considerably from the substantial decrease i n abundance reported for January to A p r i l , 1960. Specimens were d i s t r i b u t e d to a maximum depth of 90 m i n January, 120 m i n February and March, and 90 m i n A p r i l , 1961. There was an increase i n the r e l a t i v e abundance at 90 43 and 120 ra from February to March, 1961; i n A p r i l , there was a small decrease at 90 m, foreshadowing a larger decrease at th i s depth i n June, 1961. The T-S-P diagrams for June and July-August, 1961 (Figs. 43 and 44) show (as happened during June and July, 1960) that occurrences of E. p a c i f i c a were not affected by the changes i n the temperature and s a l i n i t y of t r a n s i t i o n waters at intermed-iate depths. For example specimens were c o l l e c t e d at 15 m i n water with temperatures and s a l i n i t i e s ranging from about 8.3°C and 25.8 °/°° i n A p r i l (Fig. 42), to 11.0°C and 24.3 °/oo i n June (Fig. 43), to 13.0°C and 24.7 °/oo i n July-August (Fig.44). One c o l l e c t i o n , from 8 m i n July-August, was from water of 13.8°C, the maximum at which adults were found (Table 4). Between A p r i l and June, 1961, there was a decrease i n r e l a t i v e abundance at 90 m (Fig. 45 m, n) but between June and July-August, there was considerable increase at 60, 75 and 90 m (Fig. 45 n, o). Specimens were not c o l l e c t e d below 90 m i n A p r i l and June, but one c o l l e c t i o n of 7.7 animals/m 3 was made at 120 m i n July-August. Discussion of adults of Euphaiasia p a c i f i c a Temperature-salinity diagrams and geographical d i s t r i -butions of temperature, s a l i n i t y and density for waters i n Indian Arm show that within the annual ranges, conditions f l u c -tuated monthly and seasonally, or were disrupted by intrusions of outside waters. The temperature-salinity-plankton diagrams show the ranges of properties from which adult specimens of E. ' p a c i f i c a were c o l l e c t e d annually (Fig. 21) and month by month (Figs. 30 - 44). Within the t o t a l range occupied, c e r t a i n con-si s t e n t features are apparent. F i r s t l y , E. p a c i f i c a occurred over a wide range of temperature and s a l i n i t y . It was c o l l e c t e d only exceptionally from surface waters (January to A p r i l , 1960, and December, 1960, to March, 1961) or the deepest waters (June and December, 1960), features best i l l u s t r a t e d by the monthly, geographical d i s t r i -butions of specimens (Fig. 45 a to o). A l l occurrences i n the surface waters were i n winter and coincided with low tempera-tures then;and the abundance of specimens increased as the s a l i n -i t y increased (e.g., March, 1961). The waters from about 90 to 200 m varied only s l i g h t l y i n temperature and s a l i n i t y from month to month and yet specimens were not generally c o l l e c t e d below 120 m. Occurrences therefore were i n waters designated " t r a n s i t i o n " and "deep" by means of the T-S diagrams, but i t i s clea r that only the upper part of the deep water was occupied (with rare exceptions). Secondly, changes i n properties of the t r a n s i t i o n and deep waters may have one of two e f f e c t s . I f the change resulted from only seasonal fluctuations i n temperature and/or s a l i n i t y , neither the numbers of specimens . nor t h e i r occurrences (and hence d i s t r i b u t i o n ) , were greatly affected. I f , on the other hand, the changes resulted from intrusions into the i n l e t of outside waters t h e i r numbers may be reduced and/or the d i s t r i -bution alte r e d . Thus during, and c l o s e l y following,, the major intrusion i n February and March, 1960 (pp.18, 29 and 30 ). when much of the water column was affected, the numbers of 45 specimens were greatly reduced throughout the i n l e t , p a r t i c u -l a r l y during March at the maximum extent of the intrusion, and in A p r i l . It i s probable that substantial numbers.of specimens were transported out of the i n l e t along with the ^.plume displace-ment and removal of resident water by intruded water (p. 30 ) Only at Station 2, close to the head of the i n l e t and furthest removed from the influence of the intruding waters, was the abundance of specimens maintained. In the r e l a t i v e l y small intrusion which occurred between A p r i l and June, 1961 (pp.27 and 30 ) and influenced waters between 100 and 200 m, the num-ber of specimens was noticeably reduced at 90 m and none was co l l e c t e d below t h i s depth. In July-August, 1961, coincident with the decreasing influence of the intruded water (p.27 )« specimens were c o l l e c t e d at 120 m and numbers increased at 90 m (the d i s t r i b u t i o n , with respect to the deeper waters,thus resembled that during March, 1961, prior to the in t r u s i o n ) . Intrusions also s h i f t e d the centre of population of E. p a c i f i c a . Thus the intrusion which influenced waters between about 10 and 75 m during October to December, 1960 (pp. 22 and 23) only s l i g h t l y reduced the abundance, but specimens concen-trated at 90 and 120 imsat Stations 2 and 6 below and remote from the intruding waters. By January, 1961, specimens were again d i s t r i b u t e d evenly throughout the i n l e t and were not c o l l e c t e d below 90 m, coincident with the decreasing influence of the intruded water (pp.24 and.25 ). It i s important to note that the changes i n temperatures and s a l i n i t i e s during 1960 and 1961 (apart from the seasonal 46 fluctuations at the surface) were r e l a t i v e l y s l i g h t , and always within the range that E. p a c i f i c a had been shown to t o l e r a t e i n the T-S-P diagrams of Indian Arm (and i n l a t e r studies i n the laboratory). From t h i s , and the points discussed above, i t i s reasonable to i n f e r that fluctuations i n the abundance and d i s t r i b u t i o n of E_. p a c i f i c a i n Indian Arm may be related to f i r s t l y , the volume displacement and mass transport of resident water and specimens out of the i n l e t as a r e s u l t of the i n t r u s -ion of outside waters, and secondly, to the influence of envir-onmental conditions other than, or i n addition to, temperature and s a l i n i t y and associated with intruded water.. This i s p a r t i c u l a r l y evident when considering the e f f e c t s of intrusions into Indian Arm of outside waters, which while instrumental i n producing r e l a t i v e l y minor changes i n temperature and s a l i n i t y , often resulted i n major fluctuations and s h i f t s i n the occurren-ces of the resident population of E. p a c i f i c a . The s i t u a t i o n becomes the more int e r e s t i n g i n that E. p a c i f i c a occurs i n the S t r a i t of Georgia, the source of the waters intruding into Indian Arm. Despite t h i s the resident population of Indian Arm reacted adversely to the intrusions, a point returned to i n the design of the laboratory experiments. Developmental stages of Euphausia p a c i f i c a Eggs Eggs of E. p a c i f i c a were c o l l e c t e d i n Indian Arm from March to July-August, 1961, from waters with temperatures of 7.7 to 16.8°C and s a l i n i t i e s of 14.0 to 27.1 °/oo (Fig. 22; Table 4). Geographically, they were present at a l l stations and from the surface to 150 m (Fig. 29 a). Eggs were not observed i n samples from September, I960, to February, 1961, from Indian Arm. Small numbers (0.1 to 0.4 eggs/m^) were c o l l e c t e d at intermediate depths i n March, 1961 (Fig. 46). Their abundance increased i n A p r i l (Fig. 47) and June (Fig. 48) when 86 eggs/ra3 (the maximum recorded) were c o l l e c t e d at 30 m at Station 12; numbers continued to be r e l a -t i v e l y high (0.2 to 35/m3) i n July-August, 1961 (Fig. 49). In surface waters eggs were not c o l l e c t e d i n March, but were present at most stations i n A p r i l and also at Station 23 i n June (Figs. 46 - 48). By July-August (Fig. 49) they were again absent from surface waters. At intermediate depths and i n deep waters, eggs were more or less evenly d i s t r i b u t e d from Station 15 to 2 i n March and July-August and from Station 23 to 2 i n A p r i l and June. The maximum depths at which they were co l l e c t e d was 60 m i n March and 150 m i n A p r i l , June and Ju l y -August, but i n general, they appeared to be most abundant betweeo^about 15 and 60 m (Figs. 46 - 48). 48 Nauplius I Specimens of the f i r s t nauplius stage were c o l l e c t e d i n water with temperatures of 8.0 to 11.0°C and s a l i n i t i e s of 24.7 to 27.1 °/oo (Fig. 22; Table 4). Geographically, specimens occurred at a l l stations between 15 - 30 and 150 m i n Indian Arm (Fig. 29 b). In general,they were more r e s t r i c t e d with respect to temperature and s a l i n i t y (and geographical range) than the eggs. The f i r s t nauplius stage was c o l l e c t e d i n Indian Arm only during A p r i l , June and July-August of 1961 (Figs. 50-52 and i n s e r t s ) . In A p r i l (Fig. 50) they were present at a l l sta-tions, i n r e l a t i v e l y cool (8.0 to 8.7°C), h i g h - s a l i n i t y (26.0 to 27.0 °/oo) water between 15 and 120 m. In June specimens were absent from the warm,low-salinity waters between 0 and 30 m, but were concentrated i n the cooler (8.0 to 8.8°C), h i g h - s a l i n i t y (26.0 to 27^15 °/oo) waters from 45 to 150 m (Fig. 51); occurren-ces were r e s t r i c t e d to Stations 2, 9 and 12, with specimens apparently concentrated at Station 9. In July-August (Fig. 52) the majority of specimens were co l l e c t e d from water with temperatures of 8.0 to 8.8°C and s a l -i n i t i e s of 26.0 to 27.1 °/oo; small numbers, however, were present i n water of 9.0 to 11.0°C and 24.7 to 25.9 °/oo. The geographical insert shows that with the exception of one c o l l e c -t i o n at 30 m at Station 6, specimens were not c o l l e c t e d nearer the surface than 50 - 60 m during July-August. In contrast with the r e s t r i c t e d d i s t r i b u t i o n i n June, specimens were co l l e c t e d from Stations 2 to 15. 49 The abundance of specimens at the sampling locations i n A p r i l , June and July-August, 1961, ranged from 0.1 to 9.0 specimens/ra 3. This represents a large reduction i n abundance (approximately 90 %) from that of the eggs. Nauplius II Specimens of the second nauplius stage were co l l e c t e d at temperatures of 7.85 to 10.3°C and s a l i n i t i e s of 25.6 to 27.18 °/oo, but predominantly i n the range of 7.85 to 8.7°C and 25.8 to 27.18 °/oo ( i . e . , the deeper waters — F i g . 2 3 , dotted l i n e s ) . The geographical presentation (Fig. 29 c) indicates that, over the course of several months, specimens occurred at a l l stations, between 15 and 180 m i n Indian Arm. A notice-able feature of the geographical occurrences i s the absence of specimens from 0 to 7 5 - 90 m at Station 6 and 9, from which i t appears that the tendency to occur i n deeper water shown by the f i r s t nauplius stage has continued. In the period from September, 1960, to July-August,1961, the second nauplius stage was c o l l e c t e d i n Indian Arm only during A p r i l , June and July-August, 1961. The T-S - P diagrams (Figs. 53 - 55) indicate that specimens occurred i n cool, high-s a l i n i t y waters within l i m i t e d ranges of temperatures (7.85 to 8.7°C) and s a l i n i t i e s (25.8 to 27.18 °/oo) during these months. One exception was the small c o l l e c t i o n i n water of 10.3°C and 25.6 °/oo i n July-August (Fig.55). In A p r i l specimens were c o l l e c t e d between 15 and 180 m, but not i n any samples at Station 6 or between 0 and 90 m at Station 9. During June and July-August specimens were not c o l l e c t e d from the warmer, low-salinity waters 50 between 0 and 50 m, but were present i n the cooler h i g h - s a l i n i t y , deeper waters (Figs. 54 and 55); i n June, they appeared to be concentrated between 7 5 and 180 m at Station 9, and i n July -August, between 90 and 150 m at Stations 12, 9 and 2. The abundance of specimens ranged from 0.3 to 1440 specimens/m 3. This represents an increase (approximately 36%) over that of the f i r s t nauplius stage for the same months. Metanauplius Specimens of the f i n a l naupliar stage, the metanauplius, were c o l l e c t e d at temperatures of 7.85 to 9.4°C and s a l i n i t i e s of 25.6 to 27.18°/oo (Fig. 23; Table 4). They occurred most frequently, however, (Figs. 56 - 58), at temperatures of 7.85 to 8.5°C and s a l i n i t i e s of 26.0 to 27.18 °/oo. Geographically (Fig. 29 d and 56 - 58) metanauplii were more li m i t e d i n t h e i r horizontal and v e r t i c a l occurrences than either of the preceding stages. Specimens were not c o l l e c t e d at Station 23 and i n gen-e r a l , not from waters above 50 m i n Indian Arm; nor were they c o l l e c t e d from much of the water column (between 0 and 90 to 120 m) at Stations 2, 6 and^9S.. Thus, the deepening trend i n the v e r t i c a l d i s t r i b u t i o n of specimens, f i r s t observed i n the f i r s t nauplius stage (as opposed to the d i s t r i b u t i o n of eggs) and con-tinued i n the second nauplius stage, i s most apparent i n the occurrences of metanauplii. The abundance of metanauplii ranged from 0.1 to 8.0 specimens/m3. This was s i m i l a r to the abundance of the f i r s t nauplius stage but represented a decrease of approximately 43% from that of the second nauplius stage for the same period. 51 Calyptopis I, II and III Specimens of the f i r s t , second and t h i r d calyptopis stages, as a group, occurred i n water with temperatures of 8.0 to 12.5°C and s a l i n i t i e s of 23.4 to 27.18 °/oo (Fig.24), The c a l y p t o p i i are thus the f i r s t developmental stagesin which the re l a t i o n s h i p to temperature and s a l i n i t y approximates that of adult E. p a c i f i c a for the same period (Figs. 21, 36, 37 and 42 - 44). The in d i v i d u a l stages were c o l l e c t e d (Table 4) i n sim i l a r ranges of temperature and s a l i n i t y . The ''annual" T-S-P diagram and the geographical occurrences demonstrate a s i g n i f i c a n t broadening of the d i s t r i b u t i o n a l range of calyp-t o p i i , with respect to temperature, s a l i n i t y and depth, over that of the preceding naupliar stages. Calyptopii were c o l l e c t e d i n Indian Arm during Septem-ber and October, 1960,and from A p r i l to July-August, 1961. They occurred i n minimal numbers during September and October (Figs. 59, 63 and 67) were absent from c o l l e c t i o n s i n December through March, re-appeared i n A p r i l (Figs. 60, 64 and 68) were most abundant i n June (Figs. 61, 65 and 69) and continued i n high numbers into July-August (Figs. 62, 66 and 70). The t h i r d calyptopis stage, unlike the f i r s t and second stages, was not c o l l e c t e d i n September, but was present i n October. The abun-dance of specimens was si m i l a r for the three stages, ranging from 0.1 to 11 - 12/m3; the abundance of the f i r s t calyptopis stage represented an increase of approximately 27% over that of the metanauplius. 52 The monthly T-S-P diagrams and geographical occurrences for the f i r s t calyptopis stage (Figs. 59 - 62) show that speci-mens were c o l l e c t e d from waters with a broad range of tempera-ture and s a l i n i t y , between 8 and 180 m. Excepting for surface waters, specimens occurred throughout the i n l e t i n June, 1961 (Fig. 60) which i s a broad d i s t r i b u t i o n when compared with the li m i t e d occurrences of the metanauplius. The monthly T-S-P diagrams for the second calyptopis stage (Figs. 63 - 66) indicated that specimens were not co l l e c t e d from waters which the inserted geographical p r o f i l e s show were deeper than 120 m. The absence of specimens at 150 and 180 m i n June and July-August (Figs. 65 and 66) contrasts with the occurrences of the f i r s t calyptopis stage at these depths. From t h i s , i t appears that the second calyptopis stage i s the f i r s t l a r v a l stage which begins to approximate the v e r t i c a l d i s t r i b u -t i o n of adult specimens of Euphausia p a c i f i c a i n Indian Arm. The t h i r d calyptopis stage (Figs. 67 - 70) was c o l l e c t e d i n waters with a r e l a t i v e l y wide range of temperature and s a l i n -i t y , between 8 and 100 m. Specimens were not c o l l e c t e d at 120 m and, as with the second calyptopis stage, were also absent at 150 and 180 m. The small c o l l e c t i o n s of the t h i r d calyptopis stage at 30 m at night and at 60 m during daylight i n October, I960 (Fig. 67), provided the f i r s t suggestion of a d i e l v e r t i c a l migra-t i o n of a developmental stage. 53 F u r c i l i a I, III and VI The d i s t r i b u t i o n and relationships to temperature and s a l i n i t y of the f i r s t , t h i r d and si x t h f u r c i l i a stages were selected as being representative of the seven stages i n th i s developmental sequence of Euphausia p a c i f i c a . In general, the annual T-S-P diagram (Fig. 25) and the geographical occurrences of the f u r c i l i a stages (Fig. 29 f) were sim i l a r to those for the adult (Figs. 21 and 28 a) E. p a c i f i c a . They were c o l l e c t e d from water with temperatures of 8.0 to 13.8°C and s a l i n i t i e s of 23.3 to 27.18 °/oo (Fig. 25) with one exception, an i s o l a t e d occurrence of the t h i r d and si x t h fur-c i l i a s s t a g e s i n surface water of 18.5°C and 22.0 °/oo i n July-August, 1961 (Figs. 78 and 82). Other than t h i s exception, Table 4 shows that the three f u r c i l i a stages occurred i n sim i l a r ranges of temperature and s a l i n i t y . Geographically, f u r c i l i a were c o l l e c t e d at a l l stations and i n waters between 8 and 180 m (Fig. 29 f ) , plus the exceptional occurrence i n surface waters at Station 12 reported above; they were not c o l l e c t e d i n waters below 90 m at Station 9. The f i r s t and t h i r d stages were c o l l e c t e d i n small numbers i n September, 1960 (Figs. 71 and 75), were absent from c o l l e c t i o n s i n October through March, were most abundant i n June (Figs. 7 3 and 77) and continued into July-August, 1961 (Figs. 74 and 78). The si x t h f u r c i l i a stage was not c o l l e c t e d i n September 1960, but was present i n small numbers i n October (Fig. 80); t h i s stage was not c o l l e c t e d from December through A p r i l , re-appeared i n r e l a t i v e l y large numbers i n June (Fig. 81) and continued into July-August, 1961 (Fig. 82). The general abund-ance of specimens was similar for a l l the f u r c i l i a stages,rang-ing from 0.1 to 37 specimens/in 3 The l a t t e r number represents a substantial increase per unit volume over the maximal numbers recorded for the preceding t h i r d calyptopis stage. The monthly, T-S-P diagrams and geographical occurrences for the f i r s t f u r c i l i a stage (Figs. 71 - 74) indicate that specimens occurred over a wide range of temperature and s a l i n i t y i n waters between 8 and 90 m. They were absent i n c o l l e c t i o n s from surface water and from a group of samples at 120, 150 and 180 m. Their v e r t i c a l d i s t r i b u t i o n thus c l o s e l y resembles that of the t h i r d calyptopis stage. D i e l v e r t i c a l migration i n the f i r s t f u r c i l i a stage was strongly suggested by changes i n depth i n September (Fig. 71) from 30 m at night to 60 m during day-l i g h t , and i n July-August (Fig. 73) from 15 to 30 m at night to between 30 and 90 m during daylight. The t h i r d f u r c i l i a stage (Figs. 75 - 78) was c o l l e c t e d i n a wide range of conditions between 0 and 180 m, but the majority of specimens occurred between 8 and 90 m. Diel v e r t i -c a l migration of specimens i s strongly suggested i n June (Fig. 76) and takes place i n July-August (Fig. 78) and September (Fig. 75). The s i x t h f u r c i l i a stage (Figs. 79 - 82) was also c o l l e c t e d from a wide range of environmental conditions, between 0 and 150 m, but as with the t h i r d f u r c i l i a stage the majority occurred between 8 and 90 m. Diel v e r t i c a l migration appears to be firmly established i n the occurrences of the s i x t h 55 f u r c i l i a stage, as demonstrated by occurrences being c l e a r l y defined into night and day le v e l s i n June and July-August (Figs. 81 and 82). It i s of interest that with few exceptions the f u r c i l i a stages were not c o l l e c t e d below 90 m, a s i t u a t i o n that i s simi l a r to the d i s t r i b u t i o n s of the second and t h i r d calyptopis stages and adults of Euphausia p a c i f i c a . Discussion of the developmental stages of Euphausia p a c i f i c a There are variations i n d i s t r i b u t i o n among the develop-mental stages of E. p a c i f i c a . Geographically, and i n r e l a t i o n to temperature and s a l i n i t y , the eggs displayed a d i s t r i b u t i o n similar to that of the adults. Among the naupliar sta%es, however, there i s a tendency for specimens to be d i s t r i b u t e d deeper i n the water. This i s apparent f i r s t with the f i r s t nauplius stage, continues with the second nauplius stage, and culminates with the metanauplius. The naupliar stages, while free-swimming (cephalic locomotion), lack the stronger swimming appendages (abdominal pleopods and thoracic appendages) and compound eyes which begin to develop strongly i n the c a l y p t o p i i and f u r c i l i a . The p o s s i b i l i t y arises, therefore, that the naupliar stages may sink and become concentrated at deeper leve l s because of poor swimming c a p a b i l i t i e s . The absence of d i e l migration would ensure that specimens remained i n the deeper water u n t i l such time as eyes developed that were capable of perceiving l i g h t s t i m u l i and the organism could respond to the s t i m u l i . Observations i n the f i e l d indicate d i e l migrations commenced i n the t h i r d calyptopis and f i r s t f u r c i l i a stages. 56. A l t e r n a t i v e l y the naupliar stages may have concentrated i n the deep waters because conditions there were ^'preferred". The concentration of the naupliar stages contrasts with the d i s t r i b u t i o n s of c a l y p t o p i i and f u r c i l i a . In general, these l a t e r developmental stages were sim i l a r to the adults i n that they were concentrated at intermediate depths, between 8 and 90 m, with r e l a t i v e l y few or no occurrences i n deeper waters. In view of the wide range of temperature and s a l i n i t y encounteredyby c a l y p t o p i i and f u r c i l i a i n the t r a n s i t i o n waters which were present at intermediate depths, i t seems improbable that the small differences i n temperature and s a l i n i t y between these and deeper waters were instrumental i n preventing move-ments into the deeper waters. It seems more l i k e l y that other environmental factors i n these waters were responsible for the general f a i l u r e to c o l l e c t c a l y p t o p i i and f u r c i l i a (and adults) there. The intrusion of outside water which influenced environ-mental conditions between 100 and 200 m i n the i n l e t between A p r i l and June, 1961, may have provided b a r r i e r s for the entry of the second and t h i r d calyptopis stages and f u r c i l i a into the deep waters. This p o s s i b i l i t y has been previously discussed with respect to the v e r t i c a l d i s t r i b u t i o n of adult specimens i n A p r i l and June, 1961. In contrast, the naupliar stages were concentrated during these months i n a depth range which c l o s e l y coincided with the influence of the intruding waters (pp. 27 and 29 ). D i e l v e r t i c a l migration was suggested i n the t h i r d calyptopis stage, strongly indicated i n the f i r s t and second f u r c i l i a stages and firmly established i n the si x t h f u r c i l i a stage; t h i s corresponds with the progressive development i n morphology and i n p a r t i c u l a r , swimming appendages and compound eyes. The increased mobility also accorded with changes i n d i s -t r i b u t i o n , but as already shown, not i n a l l waters of the i n l e t — i . e . , specimens were "selecting" t h e i r environment. 58 Thysanoessa s p i n i f e r a The occurrences of T. s p i n i f e r a r e l a t i v e to temperature and s a l i n i t y i n Indian Arm, from September 1960, to July-August 1961, are shown i n the T-S-P diagram of F i g . 26. The enclosed area,indicating the t o t a l range of temperature (7.6 to 13.7°C) and s a l i n i t y (23.7 to 27.15 °/oo) occupied by specimens, coin-cides with intermediate-depth (transition) and deep waters. Geographically, specimens occurred (Fig. 28b) from Station 15 to 2, between 8 and 180 m, during the above period. Figures 83 - 97 are monthly T-S-P diagrams showing the occurrences and r e l a t i v e abundance of adult T. s p i n i f e r a from January, 1960, to July-August, 1961; the associated geographi-c a l d i s t r i b u t i o n s are presented i n F i g . 98 a-o. Adults were c o l l e c t e d i n a l l months except A p r i l , 1961 (Fig. 95, 98 m). Numbers ranged from 1 to 30.3 specimens/10m3 (Table 3), but more often were between 1 and 6 specimens/lOm . This was considerably less than that recorded for E. p a c i f i c a (p,39 ) Thysanoessa spinifera,appears to undergo d i e l v e r t i c a l migra-ti o n , occurring above 90 m at night and as deep as 180 m during the day. Unlike E. p a c i f i c a , a complete developmental sequence of T. s p i n i f e r a was not observed i n Indian Arm. Collections were l i m i t e d to adults, immature adults and a very few of the l a t e f u r c i l i a stages. The isol a t e d c o l l e c t i o n s of T_. s p i n i f e r a made in surface waters i n February and March, 1960 (Figs. 84, 85 and 98 b,c) were from cool, low-salinity waters. In February the temperature was 6.6°C and the s a l i n i t y 14.3 °/oo, the minimal values at which T. s p i n i f e r a was c o l l e c t e d (Table 5). 59 Thysanoessa s p i n i f e r a was c o l l e c t e d from waters of intermediate and greater depth i n January, February and March, 1960 (Figs. 83 - 85) during the period of general decrease i n temperature and increase i n s a l i n i t y associated with the major int r u s i o n of outside waters which entered Indian Arm i n Febru-ary and March (pp. 18, 19,29 and 30). There was an increase, amounting to 80%, i n the abundance of specimens from January to February, 1960 (Fig. 98 a, b). This increase was most evident at Stations 12 and 15, and i n the deeper waters at Stations 2, 6 and 9. Although the geographical occurrences of specimens were not as wide-spread i n March (Fig. 98 c) as i n February, there was an increase i n r e l a t i v e abundance at intermediate depths i n March which resulted i n the t o t a l abundance being si m i l a r i n the two months. In A p r i l , 1960, specimens almost disappeared from Indian Arm (Figs. 86, 98 d); only two small c o l l e c t i o n s were made at Stations 9 and 12. The T-S (Figs. 5 and 6) and T-S-P (Figs. 85 and 86) diagrams show that temperature increased and s a l i n i t y decreased at intermediate depths from March to A p r i l , 1960, (e.g., at 30 m, values were around 7.7°C and 27.1 o/oo i n March and 7.9°C and 26.4 °/oo i n A p r i l ) but i t seems unlikely that the small changes which occurred were d i r e c t l y responsible for the large decrease i n abundance of T. s p i n i f e r a . The temperatures and s a l i n i t i e s of the waters from which speci-mens were not c o l l e c t e d i n A p r i l were within the range occupied i n preceding and subsequent months. The T-S-P diagram for June, 1960 (Fig.87), shows a 6a continuance of the trend of increasing temperature and decreas-ing s a l i n i t y i n waters at intermediate depths, and a large increase over A p r i l (approximately twenty-fold) i n the abund-ance of specimens i n the i n l e t . Whereas at 30 m no specimens were c o l l e c t e d i n water of 7.9°C and 26.4 °/oo i n A p r i l (Fig. 86), numerous specimens were present at t h i s depth i n water of 9.5°C and 25.0 °/oo i n June (Fig. 87). Geographically, specimens occurred i n June, 1960 (Fig. 98 e), at 30 and 60 m, between Stations 15 and 6; the maximum numbers, up to 30.3 specimens/10m3, were c o l l e c t e d at 30 m at Stations 12, 9 and 6. The increase i n abundance i n June, combined with the occurrences being confined to "intermediate water" (Fig. 87), suggests that a population of T. s p i n i f e r a from outside Indian Arm may have entered at the intermediate-depths. The substantial volumes of surface runoff leaving Indian Arm and a compensating inflow at intermediate l e v e l s i n June (pp. 12 and 3) would provide the necessary means of trans-port for such an i n f l u x . The d i s t r i b u t i o n s of temperature and s a l i n i t y for June did not indicate such an inflow (pp. 19 and 20) but the p o s s i b i l i t y remains that subsurface water from outside entered the i n l e t and, because temperatures and s a l i n i t i e s were simi l a r to those i n Indian Arm, or perhaps because of mixing with resident water, i t was not detected. The decrease i n abundance from June to July, 1960, was approximately 80 %. In July (Fig. 98 f ) , specimens were evenly d i s t r i b u t e d between Stations 12 and 2, predominantly i n waters between 60 and 90 m. The reduced numbers i n waters above 60 m 61 coincides with increased temperatures i n the shallower waters; e.g., the temperature at 30 m ranged from 9 to 10.5°C i n June to 9.8 to 12.7°C i n July, 1960 (Figs. 87 and 88). Subsequent occurrences i n June and July-August, 1961 indicate, however, that even 12,7°C i s within the range "tolerated" by T.spinifera i n Indian Arm, The trend of decreasing abundance continued into September and October,1960. Accompanying the decrease was a s h i f t of specimens towards the head of the i n l e t from Stations 15 to 2 i n June and Stations 12 to 2 i n July (Fig. 98 e, f) to between Stations 9 and 2 i n September and Stations 6 and 2 i n October, 1960 (Fig. 98 g, h). In the period from June to October, 1960, the range of temperature between 30 and 180 m did not vary appreciably from month tcjmonth (Figs. 87-90). However, the T-S (Figs.8 -10 ) and T-S-P (Figs. 88-90) diagrams for July, September and October indicate an increase i n s a l i n i t y at intermediate depths. At 30 m the s a l i n i t y was about 24.8 °/oo i n July, 25.9°/oo i n September and 26.5 °/oo i n October (Figs. 88-90), but such an increase i s within the range shown (Fig.26) to be "tolerated" by T. s p i n i f e r a i n Indian Arm. There was a f i v e - f o l d increase i n the abundance of T. s p i n i f e r a by December, 1960, compared with October. This increase coincided with the period during which the tempera-ture and s a l i n i t y of t r a n s i t i o n water at intermediate depths and deep water "merged" (p.33) a process attributed to r e l a t i v e l y cool, h i g h - s a l i n i t y water intruding from outride. Geographically,. T. s p i n i f e r a was c o l l e c t e d only at 90 m 62 at up-inlet stations i n October , but i n December i t occurred from Station 12 to 2, between 30 and 180 m (Fig. 98 h, i ) . This change of d i s t r i b u t i o n , coupled with the increase i n abundance during December strongly indicates an i n f l u x of specimens accompanying the intrusion of outside waters i n t h i s month. The small c o l l e c t i o n s at 150 and 180 m at Station 6 i n December, 1960, represented one of the few occurrences of Z - s p i n i f e r a i n waters deeper than 120 m i n Indian Arm (Fig. 98 i ) . By January, 1961, there was a decrease i n abundance by approximately 60 % (Fig. 92), accompanied by a s h i f t of the remaining population toward the head of the i n l e t (Fig. 98 j ) where occurrences were li m i t e d to Stations 9, 6 and 2 between 30 and 90 m. This decrease appears to ensue on or accompany mixing between the resident and the intruded water of December (pp. 23 and 24) and presumably results from a decreasing influence of t h i s water. The abundance of specimens i n February, 1961 (Fig.93) was unchanged fromjjanuary, but geographically, occurrences were concentrated c e n t r a l l y i n the i n l e t , at Station 9 (Fig. 98 k ) . The small c o l l e c t i o n at 150 m at Station 9 represents the fourth and l a s t occurrence of specimens i n waters below 120 m. An increase of approximately 20 % i n abundance by March, 1961 (Fig. 94), was r e s t r i c t e d to waters 15 to 90 m i n depth (Fig. 98 1) over the length of the i n l e t . A small intrusion of outside water may have entered Indian Arm, between approximately 10 and 60 m (p,25) during t h i s time. 63 No specimens were c o l l e c t e d i n A p r i l , 1961 (Figs. 95 and 98 m). Thus there was a large reduction between March and A p r i l of 1961 which was si m i l a r to that recorded for the same months of 1960. Thysanoessa s p i n i f e r a re-appeared i n c o l l e c t -ions from Indian Arm i n June, 1961 (Fig. 96). The majority were present at 15 m at Station 15 (Fig. 98 n) near the mouth, suggesting specimens may have been entering from outside waters and between June and July-August, lg\61 (Fig. 97) there was a ten-fold increase. The s i t u a t i o n i n these months resembles that of June, 1960, when the c i r c u l a t i o n pattern of surface outflow and subsurface inflow i n Indian Arm provided a possible explanation for a large i n f l u x of specimens. Discussion of Thysanoessa s p i n i f e r a Thysanoessa s p i n i f e r a occurred over a r e l a t i v e l y wide range of temperature and s a l i n i t y i n Indian Arm, but only occas-i o n a l l y below 120 m (February, September and December, 1960$: and February, 1961) and r a r e l y i n surface water (February and March, 1960). From the T-S-P diagrams (Figs. 26, 8 3 - 9 7 ) i t i s appar-ent that from month to month the waters from about 90 to 200 m displayed only small ranges i n temperature and s a l i n i t y so that the near-absence of specimens below 120 m would not appear to r e s u l t from changes i n these properties. By and large, therefore, occurrences were confined to intermediate depths and to upper l e v e l s of the deep waters. The near-absence of specimens i n surface waters possibly can be attr i b u t e d to the low s a l i n i t i e s and extremes of temperature 64 there. This s i t u a t i o n contrasts with the occurrences of Euphausia p a c i f i c a at the surface i n low-salinity water during periods of seasonal cooling (p. 3.8). For the few c o l l e c t i o n s of T. s p i n i f e r a from surface waters (made at night i n February and March, 1960 (Figs. 84, 85 and 98 b, c) the minimal tempera-ture was 6.6°C, s l i g h t l y higher than the 5.3°C for E. p a c i f i c a , and the minimal s a l i n i t y was 14.3 °/oo, compared with 7.0 °/oo for E. p a c i f i c a (Table 5). I t i s possible therefore, that T. sp i n i f e r a may be less "tolerant" to temperature and s a l i n i t y extremes i n surface waters than E. p a c i f i c a . It seems that T. s p i n i f e r a may have been recruited into Indian Arm during periods when outside waters were entering. In general, when temperatures and s a l i n i t i e s indicated the presence or possible presence, of intruding waters (February, March and December, 1960, March and June, 1961) or when the c i r c u l a t i o n pattern was seasonally predisposed to subsurface inflows into the i n l e t because of high runoff of freshwater (June and July, 1960, June and July-August, 1961) there were associated increases i n the abundance of T. s p i n i f e r a . The geographical occurrences demonstrated that these increases were most apparent at stations i n proximity to the mouth of the i n l e t (Fig. 98 b, c, e, i , n, o). During periods i n which intruding waters were not observed or when t h e i r influence was decreasing, and when seasonal, subsurface inflows into the i n l e t were reduced (January, April,September and October,1960, January, February and A p r i l , 1961), there was a corresponding, general decrease i n the abundance of T. s p i n i f e r a , a decrease which i n i t i a l l y was most apparent near the mouth. The abundance of specimens i n January, February and March,1960 (when a major intrusion of outside water i s believed to have influenced con-di t i o n s i n Indian Arm between 10 and 200 m), compared with the few that were present i n January, February and March, 1961 (during a period when r e l a t i v e l y stable conditions prevailed), i s a strong i n d i c a t i o n of the association between intruded water and the presence of T_. s p i n i f e r a i n Indian Arm. Furthermore,the (isolated occurrences of specimens at the surface were coincident with the large intrusion i n February and March, 1960. In January, 1960, p r i o r to t h i s intrusion, and i n subsequent months i n which intruding waters were of less importance or were not observed, specimens were not observed i n surface waters. The T-S diagrams and the d i s t r i b u t i o n s of temperature and s a l i n i t y have shown previously (pp. 16 and 17, 20 ard 21,26, 2 9 - 3 1 ). that the intrusions of outside waters i n general produced lower temperatures and i n p a r t i c u l a r , higher s a l i n i t i e s i n Indian Arm. This leads to the preliminary suggestion that the increases of T. s p i n i f e r a , coincident with these intrusions, may be related therefore to the temperature and s a l i n i t y of the intruding water. The annual and monthly T-S-P diagrams i n d i -cate, however, that the ranges of temperature and s a l i n i t y of subsurface waters during periods when intrusions were not detected (e. g., between 10 and 200 m, from February to March, 1961, ranges were 7.77 - 8.0 °C and 25.2 - 27.0 °/oo — Figs. 13 and 14) were not su b s t a n t i a l l y d i f f e r e n t from those i n months i n which there were intrusions (between 10 and 200 m from February to March, 1960, ranges were 7 .1 to 8 i 2 ° C and 26.0 to 27.3 °/oo — Figs. 4 and 5 ) . In either case the tem-peratures and s a l i n i t i e s of the subsurface waters were within the ranges over which specimens were c o l l e c t e d (Fig. 26) , i . e . within the l i m i t s "tolerated". The evidence presented suggests that the presence or absence, and abundance of T. s p i n i f e r a i n intermediate-depth and deep waters i n Indian Arm i s associated with the con-current presence or absence of intruding waters and i s not dependent on the temperature or s a l i n i t y of water, either within ?the i n l e t or entering. Once t h i s species i s within the i n l e t , i t i s necessary to postulate that some undetermined property or properties, present i n the intruding water and/or present i n the resident water, may control i t s presence and abundance. Thyanoessa s p i n i f e r a i s probably an expatriate species (Ekman, 1953) at or near the l i m i t of i t s range of d i s t r i b u -t i o n i n Indian Arm. There are three reasons. F i r s t l y , T. sp i n i f e r a occurred at approximately 10% of the numbers of E. p a c i f i c a and on occasion was not c o l l e c t e d (e.g., i n A p r i l , 1961); secondly, the greater part of the developmental sequence of t h i s species was not c o l l e c t e d i n the i n l e t , suggesting that i t does not reproduce there; and t h i r d l y , specimens appeared to be recruited into the i n l e t along with intrusions of out-side water. Because T. s p i n i f e r a appears to be an expatriate species i t can be regarded as a reasonably good b i o l o g i c a l indicator ( a plankton indicator species) of oceanographic events i n Indian Arm, p a r t i c u l a r l y the detection by means of i t s presence of outside waters entering the i n l e t . 67 Thysanoessa longipes The occurrences of adults of Thysanoessa longipes r e l a t i v e to temperatures and s a l i n i t i e s i n Indian Arm are shown i n the T-S-P diagram for the period from September, 1960, to July-August, 1961, (Fig. 27). The two areas enclosed by s o l i d l i n e s indicate the t o t a l ranges of temperature (7.6 to 10.3°C) and s a l i n i t y (24.5 to 27.15 °/oo) from which speci-mens were c o l l e c t e d (Table 5). Of these two areas the small one i s of a single c o l l e c t i o n from 30 m i n June, 1961; the larger one represents temperature-salinity conditions of deeper waters, from which maximum numbers were c o l l e c t e d . Geographically f F i g . 28c), T. longipes occurred between Station 15 and 2 from depths between 30 and 90 m to 200 m; specimens were not c o l l e c t e d from surface water and only occasionally from waters at intermediate depths. Figures 99-111 are the monthly T-S-P diagrams for T. longipes, from January, 1960, to July-August, 1961 and F i g . 112 a-o presents the geographical occurrences for these months. Thysanoessa longipes was c o l l e c t e d i n Indian Arm during January, February and from A p r i l to December, 1960, and from A p r i l to July-August, 1961; specimens were not c o l l e c t e d during March, 1960, nor during January, February and March, 1961. Numbers ranged from 1 to 5/10m3 (Table 3), but more usually were 1 to 3/10m3. The occurrences therefore were sporadic and abundance very low i n comparison with Euphausia p a c i f i c a . Collections of T. longipes (unlike E. p a c i f i c a and T. spinifera) did not 68 suggest that d i e l v e r t i c a l migration occurred. Juveniles (immature adults) and adults of T. longipes were collected, but not e a r l i e r developmental stages, which was similar to the occurrences of T. s p i n i f e r a , but d i f f e r e d considerably from the c o l l e c t i o n s of a l l stages of E. p a c i f i c a . The T-S-P diagrams for January, February and March, 1960 (Figs. 99 - 101) show the r e l a t i o n s h i p between tempera-ture and s a l i n i t y and the occurrences of T. longipes during the period of the major intrusion of outside water which influenced waters between 10 and 200 m i n Indian Arm(pp,i8 29,and 30) The geographical occurrences(Fig. 112 a, b, c) show that specimens were c o l l e c t e d at 60, 90 and 120 m at Station 6 i n January, at 60 m at Station 9 i n February and were absent at a l l stations i n March, 1960. This suggests that T. longipes did not accompany the entry of outside waters i n February and March, as did T. s p i n i f e r a (pp.59 and 64 ). Thysanoessa longipes reappeared i n one sample from 60 m i n A p r i l , 1960 at Station 2 (Figs. 102, 112 d). By June, 1960 (Fig. 103), specimens had s u b s t a n t i a l l y increased i n abundance and were extending up-inlet at 50-60 m from Station 23 to Station 9 (Fig. 112 e ). The small c o l l e c t i o n at 20 m at Station 23, i n waters of 10.3°C and 25.0 °/oo represents the minimum depth at which T. longipes was observed. The c i r c u l a t i o n pattern during t h i s period (pp.12 and 13 ) would provide the necessary means for transport of T. 69 longipes into Indian Arm, a s i t u a t i o n comparable to that reported for T. s p i n i f e r a (p. 60) for June, 1960. By July, 1960 (Figs. 104, 112 f ) , T. longipes was more abundant than i n June and was centered i n two pockets, one up-inlet at Stations 6 and 2 and the other at Stations 15 and 12. This d i s t r i b u t i o n could have resulted from a movement towards the head of the i n l e t of those specimens that had entered i n June, combined with a continuing entry of specimens into the i n l e t . In September and October, 1960, T. longipes was reduced to single c o l l e c t i o n s of specimens (Figs.105 and 106) which were deep and towards the head of the i n l e t (Fig. 112 g, h). The T-S and T-S-P diagrams for September (Figs.9 and 105) indicate that the temperatures and s a l i n i t i e s between 30 and 200 m were l i t t l e changed from July (Figs. 8 and 104), and thus the decrease i n specimens from July to September does not appear to be related to these factors. The low numbers i n September and October do correspond, however, with the seasonal decrease i n surface runoff and thus a low subsurface inflow of outside water (p. 13 ). The T-S-P diagram for December, 1960 (Fig. 107) shows a large increase i n the abundance of T. longipes over October. This increase (as with T. s p i n i f e r a (p.61 )) was associated with the intrusion which influenced water between 10 and 75m (pp. 22, 23 and 30 •). Geographically, specimens were c o l l e c t e d during December i n the deeper water(60-180 m) at Stations 12, 9 and 6 (Fig. 112 i ) . The small c o l l e c t i o n s at 150 and 200 m 70 represent the only occurrences of T. longipes i n waters below 120 m. By January, 1961, despite the i n f l u x of T. longipes i n December, no specimens were co l l e c t e d (Fig. 108, 112 j ) . This s i t u a t i o n continued during February and March, 1961 (Fig. 112 k, 1). The absence of specimens between January and March was associated with a decreasing influence of the i n t r u s i o n of December (pp.24 and 30) and r e l a t i v e l y stable conditions of temperature and s a l i n i t y (p.25). . One small c o l l e c t i o n was made at 50 m at Station 15 i n A p r i l 1961 (Fig. 112 m), but by June, specimens occurred at Station 15, 12 and 9, between 30 and 120 m (Fig. 112 n). This increase coincided with an inflow of outside water at intermediate and greater depths, i n part compensating for the maximal outflow of runoff at the surface (pp. 12 and 1/3 ) and i n part r e s u l t i n g from an intrusion which influenced the i n l e t waters between 100 and 200 m (pp.27, 29 and 33) The proximity of the occurrences of T. longipes to the mouth of the i n l e t (Stations 15 and 12) suggests that the specimens accompanied these outside waters. By July-August, 1961, there had been a substantial decrease i n the abundance of longipes and an up-inlet s h i f t i n the d i s t r i b u t i o n of specimens ( F i g s . I l l , 112 o), probably r e s u l t i n g from the decreasing influence of outside waters during July-August (p.27, ). 71 Discussion of Thysanoessa longipes Waters intruding into Indian Arm v i a Burrard Inlet, and presumably o r i g i n a t i n g i n the S t r a i t of Georgia, appear to be important i n transporting T. longipes into the i n l e t I f so, they must be considered i n r e l a t i o n to the occurren-ces and d i s t r i b u t i o n of t h i s species. During periods i n which the temperatures and s a l i n i t i e s indicated intrusions of outside water (e.g., December, 1960 and June, 1961), and i n periods i n which the c i r c u l a t i o n pattern was seasonally predisposed tojsubsurface inflows of outside waters (e.g., June and July, 1960 and June, 1961),there was a correspond-ing increase i n the abundance of T. longipes, p a r t i c u l a r l y at stations located towards the mouth of the i n l e t . In general, also, during periods i n which the influence of intruded waters was decreasing, the species was rapidly reduced i n numbers or was not observed i n the i n l e t (e.g., A p r i l , September and October, 1960, January to A p r i l and July-August, 1161). Even though a primary pre-requisite for the entry of longipes into Indian Arm was the corresponding entry of outside waters, there was one notable exception, the near-absence of specimens during the major intrusion of February and March, 1960. A second and obvious pre-requisite for the entry of T. longipes into Indian Arm i s i t s presence i n waters adjacent to the i n l e t . A comparison of c o l l e c t i o n s o f j£. longipes obtained from cruises i n Indian Arm and extended into nearly S t r a i t of Georgia i n March and J u l y -August, 1961, bears on t h i s aspect. In v e r t i c a l hauls from 0-240 m i n central and southern locations i n the S t r a i t of Georgia the number of specimens c o l l e c t e d ranged from n i l to 6 i n March, and from 10 to 63 i n July-August. Perhaps a r e f l e c t i o n of t h i s was that specimens were not c o l l e c t e d i n Indian Arm during March but were present i n small numbers i n July-August, 1961. Although the periods under discussion are not the same (March, 1960; March and July-August; 1961) the absence of specimens i n Indian Arm during March, 1960, may be at t r i b u t a b l e to an absence of t h i s species i n waters adjacent to Indian Arm, si m i l a r to the case i n March, 1961. Thysanoessa longipes usually occurred between 60 and 120 m, i n a r e l a t i v e l y narrow range of temperature and s a l i n -i t y . Exceptions were the c o l l e c t i o n s made at 20-30 m (June and July, 1960, and June, 1961) and at 150 and 200 m i n December, 1960. Outside waters are believed to have entered Indian Arm during these months. On the basis of the f i e l d study, the s c a r c i t y of specimens i n waters above 60 m may be related to the extremes of temperature and s a l i n i t y i n the upper waters. In that T. longipes was usually absent above 60 m indicates i t was less "tolerant" to these extremes than either T. s p i n i f e r a of E_. p a c i f i c a (Table 5). Thysanoessa longipes, as with T. s p i n i f e r a and E. p a c i f i c a , was infrequently c o l l e c t e d below 120 m. Exceptions were the c o l l e c t i o n s at 150 and 200 m i n December, 1960, when an intrusion of outside waters entered Indian Arm at depths between 10 and 75 m. The T-S-P diagrams show that on a month' by month basis the fluctuations i n the temperature and s a l i n i t y of waters between 60 and 200 m i n the i n l e t were r e l a t i v e l y s l i g h t over the two-year period, and as such would not appear to account for the fluctuations of T. long- ipes . The above points indicate that the various influxes of specimens and t h e i r b r i e f survival i n Indian Arm may be related to environmental conditions other than temperature and s a l i n i t y . Because, f i r s t l y no specimens were c o l l e c t e d over several months and when present they were i n low abundance (approximately 2% that of the resident species, E. p a c i f i c a ) , secondly, the absence of a developmental sequence of the species i n the i n l e t , and t h i r d l y , the association of speci-mens with the entry of outside waters, T. longipes i s regarded as an expatriate species i n Indian Arm and probably at or near the l i m i t s of i t s d i s t r i b u t i o n a l range. As such t h i s species, when present, i s useful as a b i o l o g i c a l i n d i c a -tor, p a r t i c u l a r l y of those outside waters which may have entered recently, or be entering the i n l e t . 74 Thysanoessa r a s c h i i The occurrences of adults of Thysanoessa raschi are shown i n r e l a t i o n to temperatures and s a l i n i t i e s i n Indian Arm, from September, 1960, to July-August, 1961 (Fig. 27). In t h i s T-S-P diagram, four areas enclosed by dotted l i n e s indicate the t o t a l ranges of temperature (8.8 to 11.7°C) and s a l i n i t y (25.7 to 26.8 °/oo) i n waters of intermediate depth from which specimens were c o l l e c t e d . The developmental stages of T. r a s c h i i were not observed i n Indian Arm. Geographically (Fig. 28 d) T. r a s c h i i was c o l l e c t e d at Station 15 and 12, between 30 and 50 m, and at Stations 6 and 2 at 60 m. Specimens were not c o l l e c t e d above 30 m, or deeper than 60 m. Figures 113 - 117 are monthly T-S-P diagrams, with accompanying inserts of the geographical d i s t r i b u t i o n of specimens, showing the occurrences and r e l a t i v e abundance of T. r a s c h i i i n Indian Arm between January, 1960, and J u l y -August, 1961. Numbers ranged from 1 to 6/10m3 (Table 3), but more usually were 1 toP; 2710m3. This i s the lowest abundance among the four specieism^ of euphausiid co l l e c t e d ; T. r a s c h i i also was the most sporadic i n i t s occurrences. The highest numbers (4 to 6/1Om3) were present towards the mouth of the i n l e t i n July and September, 1960, and i n July-August, 1961 (Figs. 113, 114 and 117). Other small, i s o l a t e d c o l l e c t i o n s were made at Station 2 i n October and at Station 6 i n Decem-ber, 1960 (Figs. 115 and 116); specimens were not observed 75 i n the i n l e t from January to June of 1960 and 1961. From t h i s i t appears that T. r a s c h i i entered from outside waters i n the summer and early autumn, s h i f t e d towards the head of the i n l e t and decreased i n numbers i n l a t e autumn and early winter, and was absent for the remaining winter months and spring. Discussion of Thysanoessa r a s c h i i Substantial movements of water, such as intrusions of outside water, were not detected i n the i n l e t during July to September of 1960 and July-August, 1961, when T. r a s c h i i was most abundant. Furthermore, seasonal runoff at the surface and compensating inflows of subsurface water (PP-12 and 13 ) were decreasing i n July and were minimal i n August and September. Thus the means of transport, shown to be associated with the entry of T. s p i n i f e r a (pp.60 and 64 ) and T. longipes (p.68 ) into Indian Arm, either were not apparent or were reduced for the periods during which T. r a s c h i i entered. The oceanographic conditions, and the occurrences of r a s c h i i , i n waters adjacent to Indian Arm, may provide some explanation for the occurrences of t h i s species within the i n l e t . Waldichuck (1957) reported that a warm, high-s a l i n i t y water at intermediate depths intrudes into the S t r a i t of Georgia from Juan de Fuca S t r a i t i n l a t e summer (August to September), and by l a t e autumn has formed i n t e r -mediate and deep waters with d i f f e r e n t c h a r a c t e r i s t i c s from those which occur i n winter (Waldichuck, 1957). There are 76 indications, too that T. r a s c h i i i s most abundant i n the S t r a i t of Georgia during the summer months. For example,in 1965, i n a series of c o l l e c t i o n s i n the southern S t r a i t of Georgia, the average number/tow was 24.7 i n March, 4.8 i n A p r i l and 46.2 i n July (personal communication, P a c i f i c Oceanographic Group). S i m i l a r l y , i n 1962, i n c o l l e c t i o n s from Saanich Inlet, an i n l e t adjacent to the S t r a i t of Georgia, the numbers/plankton tow averaged 34 specimens i n January, 2.3 i n May and 1,562 i n July (unpublished data. I n s t i t u t e of Oceanography, University of B. C.). Over the twojyears of the present study i n Indian Arm, approximately 85 % of the specimens were c o l l e c t e d during July, August and September. This coincides i n a general way with the increased abundance of specimens i n outside waters i n July and, i n turn, with the summer in t r u s i o n of "oceanic" water into the S t r a i t of Georgia. That i s , presence of T. r a s c h i i i n Indian Arm during the summer and absence during the winter accords with the seasonal changes i n the water masses of the S t r a i t of Georgia - Juan de Fuca S t r a i t system. The plankton data, while sparse, suggests that T. r a s c h i i , a species inhabiting oceanic-coastal mixed waters, probably accompanied the summer int r u s i o n of "oceanic" water into the S t r a i t of Georgia, and thence into Indian Arm. On the other hand, the decrease to apparent absence of specimens i n Indian Arm i n the winter and spring coincides with a decrease i n the influence of the "oceanic" intrusion and a return to winter conditions i n the S t r a i t of Georgia. 77 The occurrences of T. r a s c h i i were i n a narrow range of depth, between 30 and 60 m i n Indian Arm. This may be an ind i c a t i o n that the specimens remained within the confines of small and undetected volumes of outside water entering at pa r t i c u l a r density l e v e l s . The i n t e g r i t y of thi s water even-t u a l l y would be destroyed through mixing with resident water i n Indian Arm. The f a i l u r e to c o l l e c t T. r a s c h i i i n waters above 30 m may be related to the extremes of temperature and s a l i n i t y i n the upper waters of Indian Arm. In pa r t i c u l a r , the di l u t e d surface waters during periods of runoff would subject speci-mens to s a l i n i t i e s considerably lower than those encountered i n outside waters. The maximum depth at which specimens occurred (60 m) i n Indian Arm, however, does not appear to be related to temperature and s a l i n i t y . The waters below 60 m are characterized by r e l a t i v e l y low temperatures and high s a l i n i t i e s and have considerably less v a r i a t i o n i n temperature and s a l i n i t y than the waters (30 to 60 m) i n which T. r a s c h i i was c o l l e c t e d . Furthermore, the temperature and s a l i n i t y of deeper waters would be closer to those of outside waters from which specimens originated. Thus, with regard to temperature and s a l i n i t y , i t would appear that the waters below 60 m were as suitable as the waters between 30 and 60 m, for an oceanic-coastal species such as T. r a s c h i i . The most notable feature was the presence of T. r a s c h i i i n Indian Arm during July and September, 1960 and July-August, 1961 and i t s r a r i t y or absence i n a l l other months. Neither 78 temperature nor s a l i n i t y appeared to be a causative factor i n these fluctuations. For example, from June (no specimens collected) to July (4 specimens/10m3) and from September (as high as 6 specimens/lOm 3) to October (one specimen/10m3) the ranges i n these properties (Figs. 7-10) were well within the "range tolerated" by T. r a s c h i i as shown in the annual T-S-P diagram. It appears, therefore, that the sporadic occurrences of T. r a s c h i i were not associated with changes i n temperature and s a l i n i t y . It i s suggested that the occur-ences between July and December and t h e i r not being c o l l e c t e d during January to June were related to other undetermined environmental conditions. On the basis of the rare occurrences and l i m i t e d d i s -t r i b u t i o n of specimens i n Indian Arm, the absence of a devel-opmental sequence of the species i n the i n l e t , and the suggestions that the presence of specimens i s associated with oceanographic changes i n the S t r a i t of Georgia, T. r a s c h i i i s regarded as an expatriate species i n Indian Arm and probably at or near the l i m i t s of i t s d i s t r i b u t i o n a l range i n the i n l e t . As with T. s p i n i f e r a and T. longipes t h i s species may be p o t e n t i a l l y useful as a b i o l o g i c a l i n dicator. 79 V. VERTICAL MIGRATION OF EUPHAUSIA PACIFICA IN RELATION TO TEMPERATURE AND SALINITY: PRELIMINARY OBSERVATIONS FROM INDIAN ARM Daily changes i n v e r t i c a l d i s t r i b u t i o n of planktonic organisms r e s u l t from v e r t i c a l migrations of specimens,by which they ascend into the upper waters at night and return to the deeper waters during daylight. I t i s , therefore, only during the night that migrating animals could encounter the regions of maximum temperature and s a l i n i t y change ( i . e . , the thermocline and halocline) c h a r a c t e r i s t i c of upper waters i n Indian Arm (p. 33 ). F i e l d observations provided the f i r s t indications that temperature and s a l i n i t y may exert important e f f e c t s on the v e r t i c a l migration of Euphausia p a c i f i c a i n Indian Arm. Figures 118, 119 and 120 consist of temperature-depth and salinity-depth curves i n r e l a t i o n to the numbers of E. p a c i f i c a c o l l e c t e d during selected months. C o l l e c t -ions were'obtained from 0, 8, 15, 30 and 45 m i n upper waters and from 60, 75, 90, 120, 150 and 180 m. In February, 1961 (Fig. 118) only a few specimens (2/10m3) were c o l l e c t e d at the surface. A strong h a l o c l i n e (6.8 - 25,4 °/oo, from 0 to 5 m) was present, r e s u l t i n g i n a mean s a l i n i t y gradient of 3.7 °/oo/m i n the upper waters. In March, 1961 (Fig;l !L0) an increased c o l l e c t i o n (12/10m3) was made at the surface at night, associated with a moderate halo c l i n e (19.5 - 26.0°/oo, from 0 to 10 m) and a weak thermocline (7.3 - 8.4°C, from 0 to 10 m). In June, 1961 (Fig. 120) E. p a c i f i c a was not co l l e c t e d i n surface waters. At t h i s time there was a strong h a l o c l i n e (12.7 - 23.2 °/oo, from 0 to 5 m) and a pronounced thermocline (19.2 - 12.3°C, from 0 to 5 m)result-ing i n a mean temperature gradient of 1.4C°/m i n the upper waters. Additionally, (Figs. 118, 119 and 120) the maximum concentration of E. p a c i f i c a i n each of February, March and June, 1961 (29, 30 and 78 animals/10m 3, respectively) occurred immediately below the regions of maximum tempera-ture and s a l i n i t y change, during the night tows. It appears therefore, that the thermocline and halo-c l i n e r e s t r i c t e d upward migration. Few specimens were able to reach the surface; they appear to have concentrated at, or immediately below, the thermocline and/or h a l o c l i n e . 81 PART B : LABORATORY PROGRAMME The objects of the laboratory programme were to deter-mine i f the variatio n s i n euphausiid d i s t r i b u t i o n s i n Indian Arm were the r e s u l t of reactions to ranges of temperature, s a l i n i t y and temperature-salinity combinations, or to some other property or properties acting within the temperature-s a l i n i t y ranges of the waters. The procedures were directed to assessing the follow-ing: 1. the eff e c t s of separate temperature and s a l i n i t y structures on the v e r t i c a l migration of specimens, 2. the eff e c t s of combined temperature and s a l i n i t y structures on the v e r t i c a l migration of specimens, a condition comparable to that found i n the f i e l d , , 3. the ef f e c t s of "home" and "foreign" waters, where temperature and s a l i n i t y were not l i m i t i n g , on the v e r t i c a l migration of specimens, and 4. the ef f e c t s of "home" and "foreign"waters (where temperature and s a l i n i t y variations were eliminated) on the survival of specimens. Euphausia p a c i f i c a i s the dominant euphausiid i n Indian Arm and the above tests mainly concerned the adults of t h i s species. Other tests were made to determine the ef f e c t s of temperature on the v e r t i c a l migration of Thysanoessa s p i n i f e r a and of s a l i n i t y on the v e r t i c a l 82 migration of Thysanoessa s p i n i f e r a and Thysanoessa longipes. Tests on the developmental stages of E. p a c i f i c a were li m i t e d to the ef f e c t s of s a l i n i t y on the v e r t i c a l migration of fur-c i l i a . 83 VI. MATERIALS AND METHODS COLLECTIONS OF SPECIMENS AND WATER Between A p r i l , 1964, and A p r i l , 1966, l i v e specimens and seawater were c o l l e c t e d from one stat i o n i n each of Indian Arm, S t r a i t of Georgia and Juan de Fuca S t r a i t (Fig. 1 b 7 A, C, D)• seawater also was c o l l e c t e d once from Malas-pina S t r a i t , (Fig. 1 b-B) i n the northeast S t r a i t of Georgia. To compare with re s u l t s of the preceding study of the d i s t r i b u t i o n of euphausiids i n Indian Arm the greater part of the laboratory study was concerned with specimens from the i n l e t . The c o l l e c t i o n s were made at a central l o c a t i o n (Station 9 - F i g . 1 a J i n the i n l e t . V e r t i c a l plankton hauls were made with a one-metre r i n g net from 150 m to the surface at the three selected locations i n Indian Arm, S t r a i t of Georgia and Juan de Fuca S t r a i t . Precautions were taken to minimize the p o s s i b i l i t y of mechanical and/or physiological damage to specimens. A towing speed of approximately twojknots (lm/sec) was selected as being slow enough to l i m i t mechanical damage to specimens and yet to catch the faster-moving adults. The short, wide standard metal bucket,was replaced by one of 7.5 cm internal diameter and 62 cm long, of poly - v i n y l - c h l o r i d e . This should further reduce the mechanical damage by reducing turbulent action within the bucket while towing, and the p o s s i b i l i t y of physiological damage by reducing the amount of mixing within the bucket during the ascent from high-84 s a l i n i t y to lo w - s a l i n i t y waters. The i a t t e r point was substantiated by analyses of s a l i n i t y following a tow from 150 m to the surface i n Indian Arm during June, 1964, a period when warming and maximum . d i l u t i o n of surface water may be expected (pp.12 and 13). The s a l i n i t y of water i n the bucket was 23.17 °/oo compared with 26.96 °/oo at 150 m and 10.8 °/oo at the surface; i n the S t r a i t of Georgia i n July, 1964, the s a l i n i t y i n the bucket was 27.71 °/oo compared with 29.96 °/oo at 150 m and 17.8 °/oo at the surface. Studies both i n the f i e l d and the laboratory indicated that s a l i n i t i e s of 23.17 and 27.17 °/oo were to l e r a b l e to adult E. p a c i f i c a . In any event, specimens were immediately transferred with a dip-tube from the bucket into t w o - l i t r e isothermal (vacuum) flasks containing seawater c o l l e c t e d at the l o c a t i o n and approximate depth from which specimens were c o l l e c t e d . For example, i n Indian Arm the majority of specimens of E_. p a c i f i c a during daylight were located between approximately 60 and 90 m. Specimens, therefore, were placed i n seawater from 75 m. Seawater was c o l l e c t e d with a Van Dorn Water Sampler (16 l i t r e ) from 75 m i n Indian Arm, 100 m i n the S t r a i t of Georgia, 150 m i n Juan de Fuca S t r a i t and 50 m i n Malaspina S t r a i t . The oxygen content was 2-4 ml/1 at these locations and depths (Institute of Oceanography, University of B r i t i s h Columbia, Data Reports, 1960, 1961, 1964) which was not l i m i t i n g to s u r v i v a l . On ship-board the seawater was f i l t e r e d 85 through nylon b o l t i n g c l o t h with a mesh of 0.07 mm and put i n 5-gal. polyethylene carboys and a series of isothermal f l a s k s . Specimens and seawater from Indian Arm were taken to the laboratory within three to four hours and i n up to six hours from the S t r a i t of Georgia and Juan de Fuca S t r a i t . The number of specimens was l i m i t e d to 10 - 15/2 l i t r e s i n the isothermal f l a s k s . The temperature of the seawater i n these flasks fluctuated l i t t l e during t r a n s i t and remained within the range occupied by specimens c o l l e c t e d i n the f i e l d . In the laboratory, the seawater was f i l t e r e d through a m i l l i p o r e f i l t e r of pore si z e o.45 u and placed i n 4 - l i t r e beakers, or i n 5-gal. carboys and stored at 10° C. Ten specimens were transferred with a dip-tube from the isother-mal flasks into each of the beakers. These were placed i n an incubator at a temperature (10° C) sim i l a r to that (8.3 -9.0°C) i n the f i e l d at the depth of c o l l e c t i o n of specimens, and i n complete darkness. The beakers were loosely covered to prevent excessive evaporation. TERMS USED IN DESCRIBING /EXPERIMENTAL OBSERVATIONS The various test-conditions of temperature and s a l i n i t y i n the experimental column of water are conveniently described i n terms of structure and mean gradient. Structure i s defined as gradations i n a property of seawater (e.g., temperature or s a l i n i t y ) with respect to depth i n the experi-mental v e s s e l . Mean gradient refers to the average change in value of any property of seawater per unit of depth over 86 a given v e r t i c a l distance. In the present study a l l grad-ients are v e r t i c a l , with temperature increasing and s a l i n i t y decreasing towards the surface in the experimental column. In the various temperature structures, however, the increase was not l i n e a r i n r e l a t i o n to depth and c a l c u l a t i o n of a mean temperature gradient was based not on the f u l l range of depth, but only on that part of the p a r t i c u l a r tempera-ture structure over which there was a decrease i n the migration of euphausiids. The increase i n s a l i n i t y towards the surface was generally l i n e a r with depth, but increased i n steps of either 1.3 or 3.0 °/oo from layer to layer i n a given structure. The mean s a l i n i t y gradient (the average change per unit of depth) was calculated from the t o t a l range and depth. The terms l i m i t i n g temperature and l i m i t i n g s a l i n i t y r efer to those highest values of temperature or lowest values of s a l i n i t y beyond which no migrations occurred, i n a p a r t i c u l a r set of tes t conditions i n the laboratory. There were several sources of seawater, namely, Indian Arm, S t r a i t of Georgia, Juan de Fuca S t r a i t and Malaspina S t r a i t , which were used i n the tests of survival of Euphausia p a c i f i c a i n the laboratory. Seawater c o l l e c t e d at the same lo c a t i o n as experimental organisms i s referred to as "home" water; that c o l l e c t e d at a d i f f e r e n t location, a s "foreign" water. 87 VERTICAL MIGRATION IN THE LABORATORY The p r i n c i p a l apparatus used for t e s t s (Figs. 121 and 122) consisted of an inner, c y l i n d r i c a l column within an outer jacket, both of clear, colourless perspex; measure-ments were 57 cm high by 24.5 cm diameter (outer jacket) and 19.5 cm diameter (inner column). The capacity of the inner cylinder (the "experimental column" when containing seawater and specimens) was approximately 17.5 l i t r e s . A continuous flow of freshwater was maintained within the outer jacket; i t s temperature was 9 - 10°C. The purpose of t h i s flow was to cool the water of the experimental column (and entry tube - see below) approximately to the temperature usual i n the f i e l d , and to maintain the temperature as nearly constant as possible i n the column and thus reduce the p o s s i b i l i t y of temperature changes a f f e c t i n g the v e r t i c a l migration of specimens.„ In practice the temperature range did not exceed 1.2 C° between top and bottom of the experi-mental column which, for convenience, i s referred to as the condition of "constant temperature". A series of taps (2.5cm apart - Fig.122) permanently inserted through the outer jacket and into the experimental column, enabled water samples to be withdrawn for s a l i n i t y determinations. An entry tube, 2.5 cm i n diameter, was used to introduce specimens into the experimental column. Lance (1962) used a 40-W lamp to induce decapod larvae and adult copepods to swim upward i n columns of seawater. Preliminary tests i n the present study showed that euphausiids would swim toward a r t i f i c i a l i l lumination; a 100-W lamp, placed 20 cm above the experimental vessel, was found to be more e f f e c t i v e than lower l i g h t i n t e n s i t i e s i n inducing specimens to migrate upwards. The l i g h t inten-s i t y used (100-W) throughout the temperature and s a l i n i t y tests was not intended to simulate conditions i n the f i e l d , but rather to provide maximal inducement for specimens to migrate v e r t i c a l l y . A sheet of perspex, 0.5 cm thick, was placed on top of the vessel as a heat screen. The entire apparatus was placed i n an enclosure, consisting of plywood painted f l a t black, which prevented extraneous l i g h t from entering through the back or sides of the v e s s e l . Migration i n s a l i n i t y structures In order to obtain a s a l i n i t y structure (at nearly constant temperature) layers of water of decreasing s a l i n -i t y were successively introduced into the inner c y l i n d e r . The r e s u l t was to form a series i n which each layer was approximately 1.3 °/oo lower i n s a l i n i t y than the previous one, with the lowest s a l i n i t y at the surface. Water for each layer was siphoned slowly from a container onto the centre of a f r e e - f l o a t i n g plywood disc, 18 cm i n diameter, whence i t flowed outwards and over the preceding layer. The disc eliminated mixing as layers were being formed. A s l o t i n the disc enabled the entry tube to be f i t t e d as necessary (Figs. 121 and 122) At completion of the layer-ing, the disc was removed from the surface of the column. Alternate layers, dyed with non-toxie food colouring(Fig,123), 89 demonstrated that the layers could be maintained for up to 24 hours under conditions of constant temperature. The water for each layer was prepared by d i l u t i n g the seawater c o l l e c t e d with the specimens with d i s t i l l e d water to a pre-determined s a l i n i t y . It was aerated for 10 min and the pH determined using a Beckman pH Meter. The pH of undiluted seawater from the various locations ranged from 7.5 to 7.8; that of the d i s t i l l e d water was around 6.0. The d i l u t i o n of seawater, however, could not have affected migration tests by changing the pH as the buffering action of seawater preven-ted large reductions i n pH. For example, the minimum pH observed was 7.3,for a mixture of 8 parts of d i s t i l l e d water and 2 parts of seawater from Indian Arm. Samples of the various layers were taken for analysis p r i o r to t h e i r i n t r o -duction into the column and were withdrawn from the column (by means of the taps) on completing a t e s t . S a l i n i t y deter-minations were made with an inductively-coupled salinometer. The lower-end of the entry tube was inserted into the bottom, h i g h - s a l i n i t y layer, at approximately 52 cm, pr i o r to adding the subsequent layers. Thus the water within the entry tube was continuous with that i n the bottom layer and of the same s a l i n i t y and temperature (and si m i l a r to the temperature and s a l i n i t y i n the f i e l d at the depth of c o l l e c t -ion and the same as those at which specimens were maintained i n the incubator). The temperature i n the experimental column and entry tube was maintained by the cooling jacket within a range of about 1.2C° from bottom to top, i n the several t e s t s . Specimens were transferred with a dip-tube from the incubator to the entry tube and the majority guided into the bottom layer i n the experimental column. The over-head l i g h t was turned on and the specimens were observed over one hour, migrating from the bottom water into the waters of decreasing s a l i n i t y towards the surface. In each te s t the number of migrations which stopped i n each of the s a l i n -i t y layers was counted and then expressed as a percentage of the t o t a l number of migrations observed i n the t e s t . The specimens i n the entry tube i n which temperature and s a l i n -i t y as ecological factors had been eliminated provided a control, subject to the same conditions of l i g h t i n g as the experimental column. Differences between the v e r t i c a l migrations i n the cont r o l l e d conditions and i n the experi-mental column could be attributed to ef f e c t s of the s a l i n -i t y changes i n the l a t t e r . Migration i n temperature structures For the tests of v e r t i c a l migration i n temperature structures of constant s a l i n i t y (approximately 26.7 °/oo), the layers of water of increasing temperature and the specimens were introduced into the experimental column i n a manner si m i l a r to that used for the s a l i n i t y t e s t s . The outer cooling jacket was not used. The temperature of the bottom layer of water i n the experimental column, into which specimens f i r s t entered, was sim i l a r ( 9-10°C) to that at the depth at which euphausiids were c o l l e c t e d 91 and were maintained i n the laboratory. The subsequent layers of water were heated p r i o r to being added to the experimental column. Temperatures of the layers were obtained using a thermistor probe p r i o r to. and immediately a f t e r being added, and at completion of a t e s t . Some heat transfer occurred between the layers of water i n the column and therefore i t was not possible to accurately predetermine a given temperature structure; temperature increased towards the surface, but the increase was not l i n e a r with depth. To reduce the influence of transfer of heat during the t e s t s , these were l i m i t e d to a duration of 30 minutes. The number of migrations which stopped at the various temperatures i n a given structure was expressed as a percent-age of the t o t a l number of migrations observed i n the par-t i c u l a r t e s t . A control was established i n a vessel separate from the experimental column. This vessel contained undiluted seawater of approximately 26.7 °/oo from Indian Arm and was maintained at a temperature as nearly constant as possible (the v e r t i c a l range approximated a maximum of 1.2 C° from bottom to top). This sort of control d i f f e r e d from the " i n b u i l t " control (the entry tube) used i n the s a l i n i t y t e s t s . The technique, however, e f f e c t i v e l y eliminated temperature and s a l i n i t y as ecological factors i n the control which was also subjected to the same conditions of l i g h t i n g as the experimental column. A comparison of 92 v e r t i c a l migration i n the control with that i n the experi-mental vessel would indicate whether the temperature structure was a f f e c t i n g the migration. Migration i n combined temperature and s a l i n i t y structures In the combined temperature and s a l i n i t y structures, layers of water of increasing temperature and decreasing s a l i n i t y were introduced into the experimental column i n a manner s i m i l a r to that used for the in d i v i d u a l tempera-ture and s a l i n i t y t e s t s . Two tests were set up i n which the mean s a l i n i t y gradients were 0.39 and 0.42 °/oo/cm and the mean temperature tradients were 0.40 and 0.58 C°/cm, respectively. While these gradients were designed to simulate h a l o c l i n e and thermocline conditions i n Indian Arm, i t i s important to note that they were considerably steeper than the maximal gradients, 3.7°/oo/m (0.04°/oo/cm) and 1.4 CO/m (0.01 C°/cm), discussed for the f i e l d (p. 79) Each test was of 20 specimens-? Records were kept of the t o t a l number of migrations i n the course of one hour, the number of migrations which stopped at intermediate l e v e l s i n the experimental column, and of the temperature and s a l i n i t y at which specimens stopped. The number migrating to p a r t i c u l a r temperature/salinity ranges was then expressed as a percentage of the t o t a l number of migrations. Data obtained from previous tests i n a s a l i n i t y structure of nearly constant temperature (0.08 C°/cm between 12 and 3 cm i n the experimental column) and a temperature structure with constant s a l i n i t y (26.7 0/00) constituted controls. 93 Migration i n "home" and "foreign" waters In the tests of the v e r t i c a l migration of E_. p a c i f i c a i n "home" and "foreign" waters differences i n temperature and s a l i n i t y between the waters were kept to a minimum i n order that possible e f f e c t s on migration of other factors i n the water could be observed. Specimens and seawater from Indian Arm and Juan de Fuca S t r a i t were used i n two series of t e s t s . Each series consisted of three columns of water (Figs. 139 and 140):(a), a control of "home" water of constant s a l i n i t y ; (b), a column of "home" water with a small s a l i n i t y decrease separating lower and upper regions; and (c), a column i n which "home" water i n the lower part was separated from "foreign" water i n the upper part by a small s a l i n i t y decrease, s u f f i c i e n t to provide s t a b i l i t y and prevent a l l but minimal mixing. The range of s a l i n i t i e s i n columns b and c of the two series was 26.76 to 25.12 °/oo. The s a l i n i t y i n the controls was 26.76 and 26.06 °/00. Previous migration tests i n s a l i n i t y s t r u c t -ures showed that unrestricted migration of E. p a c i f i c a occurred i n the s a l i n i t i e s used. Temperatures i n the columns were sim i l a r and the v e r t i c a l range approximated a maximum of 1.2 C° from bottom to top. Fi f t e e n adult E. p a c i f i c a were tested for 20 minutes i n each of the three l i g h t i n t e n s i t i e s used i n each column of a series of t e s t s . The columns for the two series were li g h t e d i n turn by 100-W^ahd;6-W lamps placed 20 cm above 94 the surface, and i n i n d i r e c t room i l l u n i n a t i o n . The l a t t e r two i n t e n s i t i e s were additional to the single i n t e n s i t y (100-W) used i n the temperature and s a l i n i t y structures. The number of migrations and the positions i n the columns to which specimens migrated were recorded. The above procedures provided comparable conditions of temperature and l i g h t i n g i n the "home" water i n columns a and b, but a small s a l i n i t y decrease i n column b, separat-ing lower and upper parts. Any effects on the migrations i n column b could be att r i b u t a b l e to t h i s s a l i n i t y decrease, For columns b and c, there were comparable conditions of temperature, l i g h t i n g and change of s a l i n i t y , but i n column c "home" water i n the lower part was separated from "for-eign" i n the upper part. Differences i n the migrations between column b and c could be att r i b u t a b l e therefore to factors associated with "home" and "foreign" waters. SURVIVAL IN THE LABORATORY The survival tests were li m i t e d to one species, Ji» p a c i f i c a . In general the preliminary procedures for these tests was reported on p.85 . D i s t i l l e d water was used as a diluent where adjustment of s a l i n i t y was required. The d i s t i l l a t i o n vessel was a Barnstead Water S t i l l ; a l l sur-faces coming i n contact with water and vapours are heavily c l a d with pure block t i n . In the series of tests where d i l u t i o n was required, tests were included which would indicate the e f f e c t s , i f any, of d i s t i l l e d water. Prior to the introduction of specimens, the water i n the 4 - l i t r e beakers was aerated for 15 min and then checked for pH. Specimens were removed from the storage beakers with a dip-tube, released c a r e f u l l y on to a nylon mesh so as to remove water, and then put into the test beakers. The removal of water was p a r t i c u l a r l y important when specimens were being transferred from "home" into "foreign" waters. Specimens were fed a culture of Isochrysis galbana Parke, a green f l a g e l l a t e . The culture was suspended, cen-tr i f u g e d and resuspended twice i n the same water as that i n which euphausiids were being tested i n order to remove as much of the culture medium as possible. Survival i n d i l u t e d seawater Two tests were c a r r i e d out on the survival of E. p a c i f i c a from Indian Arm i n d i l u t i o n s of water from Indian Arm. Specimens were transferred at two-day intervals into progressively more d i l u t e d waters held i n 4 - l i t r e beakers; the transfers were continued u n t i l there was no s u r v i v a l . Survival i n these tests was compared with that i n accompany-ing controls containing undiluted seawater (26.9 °/oo) from Indian Arm. In the f i r s t t e s t the t o t a l range of s a l i n i t y i n the series of te s t beakers was 26.9 to 16.0 °/oo over 8 days, and i n the second, 26.9 to 13.5 °/oo over 12 days. The number of specimens was 10 i n the f i r s t test and i n the control and 17 i n the second test and c o n t r o l . Food consisted of 1 cc of Isochrysis /2 days mixed into the water of the control and te s t beakers. Data recorded were the % of speci-96 mens which survived each transfer to di l u t e d water and the % surviving at each time i n the co n t r o l . Observations from the above tests indicated that d i l u t i o n which most affected survival not only by the actual percentage that died but also by means of the "rate" at which specimens died. These data were prerequisite to subse-quent tests of the survival of J E . p a c i f i c a i n "home" and "foreign" waters whenever i t was necessary to adjust the s a l i n i t i e s to si m i l a r values by d i l u t i o n . Survival i n "home" and "foreign" waters In the survival tests of E. p a c i f i c a i n "home" and "foreign" waters, three populations of specimens (p.83 ) and seawater from four locations (p. 84 ) were used. Analyses of water samples c o l l e c t e d throughout the study from the selected depths indicated s a l i n i t y values ranging from 26.4 to 26.9 °/oo for Indian Arm, 29.96 to 30.8 o/oo for the S t r a i t of Georgia, 32.8 to 34.08 °/oo for Juan de Fuca S t r a i t and 29.6 °/oo for Malaspina S t r a i t . The s a l i n i t i e s were adjusted to a t o t a l range of 26.3 - 26.9 °/oo, which were well within the range inhabited by E_. p a c i f i c a i n Indian Arm and i n which specimens survived during the tests using water from Indian Arm. Special tests were run on two occasions i n which undiluted (33.1 and 32.8 °/oo) and dil u t e d seawaters (26.9 °/oo) from Juan de Fuca S t r a i t were used. In the f i r s t , the s u r v i v a l of specimens from Indian Arm at a s a l i n i t y above 97 those encountered i n Indian Arm was tested; and i n the second, the tests were to determine whether there were differences i n sur v i v a l of specimens from Juan de Fuca S t r a i t i n undiluted and di l u t e d Juan de Fuca waters„(p.94). For the tests of "home" and "foreign" waters the range of pH, approximately 7.5 - 7.8, of undiluted seawater from the various locations was considered to be ne g l i g i b l e and no adjustments were made. In waters where s a l i n i t y was decreased with d i s t i l l e d water, the maximum d i l u t i o n used was approximately 22%. Determination of pH indicated that even at t h i s d i l u t i o n the d i s t i l l e d water was s u f f i c i e n t l y buffered by the accompanying seawater (p. 89 ) and conse^ quently no adjustments were made. The oxygen concentration i n a l l waters ranged between 2 - 4 m l / l i t r e and was not l i m i t i n g to survival (p. 84 ). A l l waters were aerated p r i o r to the survival tests i n the laboratory. The i n i t i a l concentration of specimens in?the tests was 10 / 4 - l i t r e beaker (an exception to t h i s was 20/4 l i t r e s i n two tests — F i g . 144b ). The beakers were loosely covered and kept at a temperature of 10°C; 5 cc of Isochrysis was introduced into each beaker at weekly i n t e r v a l s . In each series of tests specimens were placed i n a beaker of "home" water and i n one or more beakers containing the "foreign" waters, or mixtures of "home" and "foreign" waters. The "home" water acted as a control i n which condi-tions of temperature, s a l i n i t y , pH, oxygen content, concen-t r a t i o n of specimens, darkness and food were the same as those of the "foreign" waters. From the procedure adopted, i t i s believed that differences i n survival of E. p a c i f i c a i n "home" and "foreign" waters, could be attributed to factors other than those l i s t e d above. 99 VII. EXPERIMENTAL RESULTS VERTICAL MIGRATION OF EUPHAUSIIDS IN RELATION TO SALINITY: EXPERIMENTAL OBSERVATIONS Results obtained from three species of euphausiids, and one developmental stage, demonstrate that a s a l i n i t y structure, composed of layers of successively lower s a l i n -i t i e s towards the surface i n an experimental vessel, affects the v e r t i c a l migration of euphausiids i n the lab-oratory (Figs. 124 to 129 ) . The e f f e c t i s p a r t i c u l a r l y evident where the s a l i n i t y structure includes an extreme range. In the series of tests, the t o t a l number of migra-tions of 20 animals,in-the course of one hour, ranged from 17 to 45 . The mean number of migrations per tes t was 26. Behaviour during migrations: a. i n constant temperature and s a l i n i t y (control). Euphausiids i n the control (entry) tube (Pi.87) of the experimental vessel displayed no d i f f i c u l t y i n migrating d i r e c t l y , at a sustained speed, towards the l i g h t source (100-W lamp) at the surface. Individuals often remained at the surface with no detectable, adverse reaction for periods of up to one hour of maximum illu m i n a t i o n . b. i n a s a l i n i t y structure, at constant temperature. An active, v e r t i c a l migration of specimens towards the overhead l i g h t followed t h e i r introduction into the experimental vessel at a depth of approximately 52 cm. In the 100 h i g h - s a l i n i t y layers, t h e i r swimming behaviour was similar to that i n the control tube. In the successive layers, however, the number of euphausiids able to migrate upwards (referred to subsequently as the "number of migrations" decreased and ultimately none extended beyond some low-s a l i n i t y layer i n the series, the l i m i t i n g s a l i n i t y . There were three types of swimming behaviour i n the v e r t i c a l migration of euphausiids i n s a l i n i t y struc-tures. The most frequent type produced a straight, upward migration, characterized by a progressively slower v e r t i c a l swimming speed as successive s a l i n i t y layers were encount-ered. At some d i l u t i o n , specimens would reverse d i r e c t i o n i n a slow, deliberate movement and would return to the high-s a l i n i t y waters below. The second type consisted of a straight, upward migration followed, when low s a l i n i t i e s were met, by a slow c i r c l i n g i n the v e r t i c a l plane, the c i r c l e s progressively enlarging i n an upwards d i r e c t i o n . Apparently t h i s enabled a gradual penetration into water of lower and lower s a l i n i t y . In t h i s way some migrations were v e r t i c a l l y extended to include low-salinity layers not previously entered during migrations of the usual, d i r e c t type. Even-t u a l l y the c i r c l i n g animals would enter a layer with a l i m i t -ing s a l i n i t y . Subsequently the c i r c l i n g behaviour continued, but directed downwards away from the l i m i t i n g s a l i n i t y , u n t i l at some higher s a l i n i t y the majority of specimens discontinued the c i r c l i n g and descended d i r e c t l y into the deeper waters.In: the t h i r d type of swimming, specimens migrated rapidly at 101 f i r s t (approximately 7 to 8 cm/sec), but when the l i m i t i n g s a l i n i t y was reached they reacted i n an e r r a t i c and evasive manner. Following t h i s the specimens sank passively, some-times with feeble, twitching movements, to the bottom of the experimental v e s s e l . After a short period i n the high-s a l i n i t y bottom waters, these specimens recovered and the same animals often made additional migrations. A l l three types of swimming behaviour were observed i n any one s a l i n i t y t e s t . Euphausiids i n the f i r s t and second types c h a r a c t e r i s t i c a l l y swam slowly during the migrations, which possibly enabled some physiological adjust-ment to be made to the lo w - s a l i n i t y waters. In the t h i r d type, the apparent "collapse" of specimens appeared to re s u l t from the rapid ascent into the low - s a l i n i t y waters of the experimental v e s s e l . Specimens congregated between migrations, or when the overhead l i g h t was o f f , towards or at the bottom of the exper-imental vessel i n s a l i n i t i e s approximating the range from which they were c o l l e c t e d i n the f i e l d . V e r t i c a l migration of Euphausia p a c i f i c a ; a. i n a s a l i n i t y structure at constant temperature. In F i g . 124 the res u l t s are presented of the v e r t i c a l migrations i n a series of s a l i n i t y layers of adult E. pa c i f -i c a from Indian Arm. The mean s a l i n i t y gradient was 0.4°/oo/ em (differences of 1.3 °/oo between layers) and the tempera-ture constant, (and see p. 87 ). Five tests were c a r r i e d out 102 i n water from Indian Arm, two i n water from Juan de Fuca S t r a i t and one i n S t r a i t of Georgia water. Symbols are used to d i f f e r e n t i a t e individual tests i n the three waters; also the mean percentage migration i s shown for Indian Arm water (five tests) and combined for Juan de Fuca S t r a i t (two tests) and S t r a i t of Georgia (one test) waters. As shown by the mean percentage curves (Fig. 124) migrations i n general were not influenced by d i l u t i o n u n t i l the s a l i n i t y approached about 16.5 °/oo i n Indian Arm and 21.0 °/oo i n Juan de Fuca S t r a i t and S t r a i t of Georgia waters. There was an abrupt decrease i n the percentage of migrations passing into the layers of lower s a l i n i t i e s i n a l l three waters. Ultimately no specimens succeeded i n swimming beyond a p a r t i c u l a r s a l i n i t y layer. For Indian Arm water t h i s l i m i t i n g s a l i n i t y was approximately 8.5 °/oo, and for Juan de Fuca S t r a i t and S t r a i t of Georgia waters, approx-imately 13.0 °/oo. The animals therefore "tolerated" approximately 4 - 5 °/oo lower s a l i n i t y i n Indian Arm water ( i . e . , t h e i r "home" water) than i n si m i l a r s a l i n i t y structures composed of Juan de Fuca S t r a i t and S t r a i t of Georgia waters ( i . e . , "foreign" waters). This i s an important feature. A comparison of the two migration-salinity curves i n F i g . 125 indicates no s i g n i f i c a n t differences i n migration behaviour between the adults and a la t e f u r c i l i a of E . p a c i f i c a . The s a l i n i t y corresponding to the i n i t i a l decrease i n migra-t i o n (21.3 °/oo) and the l i m i t i n g - s a l i n i t y (7.5 °/oo) were the same for both. 103 In F i g . 126 the percentage migrations of E. p a c i f i c a are compared for s a l i n i t y structures i n which the decrease was approximately 1.3 °/oo and 3.0 °/oo per layer. In the structure with the lesser rate of change between layers migrations were unaffected between 26.5 and 16.8 °/oo, but were reduced at lesser s a l i n i t i e s u n t i l the l i m i t i n g s a l i n -i t y was reached between 9.5 and-8 °/oo (Fig. 126 A). When the s a l i n i t y difference between layers approximated 3.0 °/oo, migrations began to decrease at less than 21.7 °/oo and ceased between 15.2 and 11.1 o / 0 0 (Fig.126 B). These data indicate that migrations become r e s t r i c t e d to higher s a l i n i t i e s when the difference between successive layers i s increased from 1.3 to 3.0 °/oo. b. Migrations i n r e l a t i o n to maximal and minimal s a l i n i t i e s . Whereas the s a l i n i t y range i n the previous tests (Figs. 124, 125 and 126) was designed to include the maximal and minimal s a l i n i t i e s encountered by specimens i n Indian Arm (7.0 to 27.4 °/oo), there was some interest i n observing the migration of E. p a c i f i c a i n s a l i n i t i e s higher and lower than those usually encountered i n Indian Arm. Tests were run of 20 adult E. p a c i f i c a from Indian Arm, migrating i n a s a l i n i t y range of 1.1 to 39.8 °/oo; results are presented i n F i g . 127. For s a l i n i t i e s of 1.1 to 26.7 °/oo, the mean percentage migration for f i v e tests i s given; for the range of 28.5 to 39.8 °/oo, the percentage migration i s for one t e s t . Speci-mens had no d i f f i c u l t y migrating v e r t i c a l l y through a t o t a l 104 range of 16.5 to 33.6 °/oOj. Progressively fewer migrations were observed into layers above and below t h i s range,and at extremes of the range, below 8.5 °/oo and above 35.0 °/oo, animals did not enter. These results indicate that both high and low extremes of s a l i n i t y l i m i t e d the v e r t i c a l migration of E. p a c i f i c a i n the laboratory. V e r t i c a l migration of Euphausia p a c i f i c a , Thysanoessa  spinfera and Thysanoessa longipes i n a s a l i n i t y structure. In F i g . 128 results are shown of tests of the v e r t i -c a l migration of E. p a c i f i c a and T, s p i n i f e r a i n a s a l i n i t y structure with gradations approximating 3.0 °/oo between lay e r s . Specimens and seawater were c o l l e c t e d i n Indian Arm. Only one t e s t with each species was possible. Results indicate that v e r t i c a l migration of E. p a c i f i c a occurred over a s a l i n i t y range of 26.5 to 15.2 °/oo, with the i n i t i a l decrease at 17.8 °/oo; migration of T. s p i n i f e r a was observed between 26.5 and 17.8 °/oo, with the i n i t i a l decrease at 21.7 °/oo. In F i g . 129 results are shown of the v e r t i c a l migra-t i o n of T. longipes i n layers with increments of 1.3 °/oo. Few specimens of T. longipes were c o l l e c t e d i n Indian Arm at any time and because of t h i s , animals and water for t h i s t e s t were c o l l e c t e d i n the S t r a i t of Georgia. Migrations occurred over a s a l i n i t y range of 29.5 to 15.0 °/oo, with the i n i t i a l decrease at 25.1 °/oo. Comparison of results obtained i n a s i m i l a r s a l i n i t y 105 structure (increments of 1.3 °/oo)with E. p a c i f i c a (Fig.l26A) and T. longipes (Fig. 129) i s questionable because the source of the waters and animals for the tests d i f f e r e d . Despite t h i s q u a l i f i c a t i o n , i t i s apparent that E. p a c i f i c a from Indian Arm, i n a s a l i n i t y structure composed of Indian Arm water, was s u b s t a n t i a l l y more "tolerant" towards changing s a l i n i t y than T. longipes from the S t r a i t of Georgia, i n a s a l i n i t y structure composed of S t r a i t of Georgia water. Because the gradations of s a l i n i t y were greater (3.0 °/oo) in'the t e s t with T. s p i n i f e r a (Fig. 128) comparison between the migration of t h i s species and T. longipes i s not v a l i d ; tests using E. p a c i f i c a (Fig. 126) have shown previously the d i f f e r i n g results obtained with s a l i n i t y structures with increments of 1.3 and 3.0 °/oo. VERTICAL MIGRATION OF EUPHAUSIIDS IN RELATION TO TEMPERATURE: EXPERIMENTAL OBSERVATIONS Results obtained from two species demonstrate that a temperature structure, increasing towards the surface, i n f l u -ences the v e r t i c a l migration of euphausiids i n the laboratory (Figs. 130, 131, and 132). The strongest e f f e c t s occurred when temperatures reached r e l a t i v e l y high values, i . e . , extreme temperatures, when compared with conditions normally met by specimens i n Indian Arm. 106 Behaviour during migrations: a. i n constant temperature and s a l i n i t y Euphausiids displayed l i t t l e d i f f i c u l t y i n migrating to the surface of a control vessel (in which the s a l i n i t y of the water was constant at 26.7 °/oo and was maintained at as nearly a constant temperature as possible — t o t a l range approximating 1.2C° from bottom to top), when stimu-lated by an overhead l i g h t . Migrations were straight and d i r e c t , and moved at a uniform speed upwards towards the l i g h t . Individuals often remained at the surface, display-ing no apparent adverse reaction to the l i g h t for the dura-t i o n of the tests, namely up to 30 minutes. The re s u l t s of one t y p i c a l t e s t i n a control vessel are shown i n F i g . 130 (t r i a n g l e s ) ; 42 migrations of 20 E. p a c i f i c a during 30 min. are represented i n the percentage values superimposed upon the temperature-depth curve. b. i n changing temperature and constant s a l i n i t y . Euphausiids displayed one type of swimming behav-iour during migrations i n the experimental vessel when temperature increased towards the surface, but s a l i n i t y was constant. It was characterized by a straight, rapid ascent at the lower temperatures, followed by a pro-gressively slower speed as higher temperatures were encountered. Ultimately no specimens migrated beyond a p a r t i c u l a r temperature (the l i m i t i n g temperature). The 107 subsequent behaviour consisted of a slow, deliberate reversal i n the d i r e c t i o n of swimming and a straight descent to lower temperatures i n the water below. In the various tests i n a column of water with chang-ing temperature, the t o t a l number of migrations of 20 euphau-s i i d s over 30 min ranged from 30 to 51, with a mean of 44 pe'r t e s t . Vertical^migration of Euphausia p a c i f i c a and Thysanoessa  s p i n i f e r a i n a temperature structure with constant s a l i n i t y . These tests were concerned so l e l y with the effects of temperature on migration of E. p a c i f i c a and T. s p i n i f e r a . Therefore s a l i n i t y was kept constant at 26.7 °/oo, approxi-mately the value i n Indian Arm at the time and depth at which experimental animals were c o l l e c t e d . Figure 130 presents the percentage of migrations of E. p a c i f i c a reaching various depths i n the control and i n one test i n which the mean temperature gradient was 0.39C°/cm (between depths of 46 and 12 cm) and a second i n which i t was 0.68 C°/cm (between depths of 46 and 36 cm). In the control, 94 °/o- of the migrations reached the surface of the v e s s e l . In the two tests, the percentage of migrations began to decrease at approximately 14°C, continued to decrease between 14° and 25°C and ceased between 25 and 26°C. There appears to be an e f f e c t on migration a t t r i b u t -able not only to high values of temperature but also to the steepness of the mean temperature gradient. The decrease i n 108 percentage migration (Fig. 130) was more pronounced when the gradient was 0.68 C°/cm, than when 0.39 C°/cm, with the most pronounced e f f e c t occurring between the range of 16.0 and 22.5°C. Thus for the gradient of 0.68 C°/cm, between these temperatures, migration decreased from 80 to 8 %, and for 0.39 C°/cm from 85 to 44 %. Further support i s seen i n F i g . 131 (which includes data from F i g . 130) wherein results are presented of the v e r t i c a l migration of E. p a c i f i c a i n four temperature structures i n which mean gradients ranged from 0.38 to 0.68 C°/cm. The general trend among the curves i s for a decrease i n the percentage migration with increasing steepness of the mean temperature gradient. The re s u l t s of a test on the ef f e c t s of a temperature structure, with a mean temperature gradient of 0.68 C°/cm, on the v e r t i c a l migration of T. s p i n i f e r a are shown i n F i g . 132. The percentage migration again decreased progressively with increasing temperature beginning at about 14°C and continu-ing up to 25°C, which was the l i m i t i n g temperature. VERTICAL MIGRATION OF EUPHAUSIA PACIFICA IN RELATION TO COMBINED TEMPERATURE AND SALINITY: a. Experimental Results of tests of the eff e c t s of combined temperature and s a l i n i t y structures on the v e r t i c a l migration of _E. pa c i f - i c a are shown i n Figs. 133 to 138 and are summarized i n Tables 6 and 7. The results i n F i g . 133 are from tests of E. p a c i f i c a 109 i n a s a l i n i t y structure with a mean gradient of 0.38 °/oo/cm combined with a mean temperature gradient of 0.08 C°/cm. The temperature gradient was present at depths (between 12 and 3 cm ) which were shallower than those at which the decrease i n migration occurred (between 39 and 9 cm - F i g . 133), and i n any case, was n e g l i g i b l e . The results i n F i g . 133 there, fore, provide a control against which e f f e c t s of the combined temperature and s a l i n i t y structures can be measured. Figures 134 and 135 show the results of tests i n which mean gradients of s a l i n i t y (0.39 and 0.42 °/oo/cm) were simi-l a r to that i n F i g . 133 (0.38 °/oo/cm) but i n which the temperature gradients were steeper, namely 0.40 C°/cm (Fig. 134) over the depth range of 42 to 14 cm, and 0.58 C°/cm (Fig. 135) over the depth range of 46 to 26 cm. In these, unrestricted migration (Table 6) was l i m i t e d at the pro-gressively higher s a l i n i t i e s of 21.3, 22.2 and 24.0 °/oo) as the mean temperature gradient increased from 0.08 to 0.40 to 0.58 C°/cm (and Figs. 133, 134 and 135). In the same tests, the ranges of s a l i n i t i e s over which migrations decreased were 19.7 - 8.5, 20.8 - 10.1, and 22.9 - 14.8 °/oo, with l i m i t i n g s a l i n i t i e s of 8.5, 10.0 and 14.8 °/oo, respectively (Table 6). Together these data indicate that i n s i m i l a r s a l i n i t y structures the more pronounced the superimposed, mean temperature gradient, the more r e s t r i c t e d w i l l be the v e r t i c a l migration of E. p a c i f i c a with respect to waters of reduced s a l i n i t y . The results of tests presented i n F i g . 136 indicate 110 that conversely, change" of s a l i n i t y can modify the effects of temperature on the experimentally:* induced migrations of E. p a c i f i c a . The two curves for the percentage migration i n Combined temperature-salinity structures (Fig. 136 b and c) show that animals migrated into water of lower temperature than when there was a temperature structure without a super-imposed/salinity structure (Fig. 136 a). The main features of these temperature-migration curves are summarized i n Table 7; i n temperature structures with s i m i l a r mean grad-ientsjof 0.41 (a) and 0.40 CP/cm (b), the 100 % l e v e l of migration was r e s t r i c t e d to a temperature of 14.7 °C when the s a l i n i t y was constant (a), but to 13.6°C when associated with a mean s a l i n i t y gradient of 0.39 °/00/cm(b). In the same tes t s , the l i m i t i n g temperatures were 25.5°C (a) and 23.0°C (b). From these data, i t appears that, i n tests with s i m i l a r temperature structures, the e f f e c t of a high tem-perature on the v e r t i c a l migration of E. p a c i f i c a i s more pronounced when a s a l i n i t y structure i s present than when i t i s absent. b. Comparison of laboratory r e s u l t s and f i e l d observations. The results of the e f f e c t s that temperatures and s a l i n i t i e s have on the v e r t i c a l migration of E. p a c i f i c a i n the laboratory have been summarized i n Figs. 137 and 138, and are compared with the range of conditions i n which the species occurred i n the f i e l d ( i n Indian Arm). In Fig.137, contour-lines representing percentages of migration (100, 75, I l l 50, 25 and n i l per cent) i n the laboratory have been drawn r e l a t i v e to a s a l i n i t y structure with constant temperature (open c i r c l e s ) , a temperature structure with constant s a l -i n i t y (closed c i r c l e s ) , and combined temperature-salinity structures (triangles and squares). A general feature of the experimental re s u l t s i s a progressive decrease i n percentage of migrations with increasing temperature (ordinate) and decreasing s a l i n i t y (abscissas). In a s a l i n i t y structure with constant tem-perature (Figs. 133, 137), migration was almost unres-t r i c t e d ( 98 to 100 % ) over a s a l i n i t y range of 26.5 to 16.5 °/oo, but decreased below 16.5 °/oo u n t i l the l i m i t i n g s a l i n i t y was encountered, at about 8.5 °/oo. In a tempera-ture structure with constant s a l i n i t y (Figs. 136 a, 137 ), migration was unrestricted ( 100% ) over a temperature range of 9.0 to 14.7 °C but began to decrease above 14.7°C u n t i l a l i m i t i n g temperature was encountered at about 25.5 °C. In the combined structures (Figs. 134, 135 and 137), migration was unrestricted over 9.0 to 13.0 - 13.6 °C and 26.9 to 24.0 - 22.2 °/oo; a decrease i n migration began at higher temperatures and at lower s a l i n i t i e s , with l i m i t i n g values occurring at 22.3 and 23.0 °C and at 14.8 and 10.0 o/oo. The "flattened" contour-lines for 100, 75 and to a lesser degree 50 % migration (Fig. 137) i l l u s t r a t e that i n combined temperature and s a l i n i t y structures migration i s reduced at lower temperatures and higher s a l i n i t i e s over the 112 migration occurring when there i s a s a l i n i t y structure with a constant temperature or a temperature structure with a con-stant s a l i n i t y . That i s , the combined structures are more r e s t r i c t i v e of migration than either temperature or s a l i n i t y structures alone. In turn, t h i s suggests that i n combined structures, temperature and s a l i n i t y "reinforce" each other and that t h i s i s r e f l e c t e d i n the reduced numbers migrating. On the other hand, the right-angle contours at 25 % and n i l percentage, and the tendency for the 50 % contour to be intermediate i n shape between these and the 75 and 100 % contours indicate that the e f f e c t s on migration of " r e i n -forcement" may become less when either temperature or s a l i n -i t y approaches a l i m i t i n g value. For example, the l i m i t i n g value ( n i l percentage) i n the temperature structure alone ( s o l i d c i r c l e s ) was 25.5 °C and i n the s a l i n i t y structure alone (open,circles) was 8.5 °/oo and these approximate 23.0°C and 10.0 °/oo for one of the combined temperature-salinity structures (Fig. 137) Apparently, i n the presence of an extreme condition i n one variable there may be only a s l i g h t additional response i n E i p a c i f i c a to the extreme i n the co-variable i n a combined structure. The ranges of temperature and s a l i n i t y over which E_. p a c i f i c a was c o l l e c t e d i n Indian Arm during one year have been included i n F i g . 137. The maximum temperature (13.8°C) and minimum s a l i n i t y (23.5 °/oo) at which specimens occurred for A p r i l to October (Fig. 137), a period when both thermo-c l i n e and halocline were strongly evident — Fig.2, c l o s e l y 113 agree with the maximum temperature and minimum s a l i n i t y values intersected by the contour of 100 % of migrations i n combined temperature-salinity structures i n the labora-tory (13.0 to 13.6°C and 24.0 to 22.2 °/oo). From December to March (Figs. 2 and 137), conditions i n the f i e l d were characterized by an isothermal structure combined with a wide range of s a l i n i t y . The minimal s a l i n i t y (7.0 °/oo) coinciding with the absence of specimens of E. p a c i f i c a i n Indian Arm during t h i s period i s si m i l a r to the minimal s a l i n i t y (8.5 °/oo) intersected by the l i n e of n i l per cent of migrations i n a s a l i n i t y structure i n which temperature was constant ( i . e . , isothermal) i n the laboratory. Thus, here again there appears to be close agreement between f i e l d and laboratory data. However, there are also d i s s i m i l a r i t i e s between the laboratory and f i e l d data. In F i g . 138 (top) the t o t a l ranges of temperature and s a l i n i t y over which E_. p a c i f i c a was c o l l e c t e d i n Indian Arm during one year have been sub-divided into two parts; f i r s t l y , a range of properties i n which specimens were abundant (zone 1); and secondly, a range i n which specimens were few or rare (zone 2). A t h i r d area delimits the range of properties from which no specimens were c o l l e c t e d (zone 3). In F i g . 138 (bottom) the range of temperature and s a l i n i t y through which E. p a c i f i c a migrated v e r t i c a l l y i n the laboratory also has been sub-divided into two parts; f i r s t l y , a range of properties within which unrestricted migration was observed (zone A); and 114 secondly, a range i n which there was decreasing migration (zone B). A t h i r d area delimits the range of properties into which no specimens migrated (zone C). A comparison of zone 1 and A i n the two diagrams indicates that maximal numbers of E. p a c i f i c a were c o l l e c t e d i n a smaller range of s a l i n i t y i n Indian Arm (27.1 to 23.5°/oo) than was observed for v i r t u a l l y unrestricted migration ( 98 -100 % ) of specimens i n the laboratory (26.9 to 16.5 °/oo). In a s i m i l a r way, zones 2 and B (Fig. 138) indicate that while the temperature-salinity conditions i n which specimens were few or rare i n the f i e l d were characterized by a large range of s a l i n i t y and r e l a t i v e l y isothermal temperatures, the comparable zone of decreasing migration i n the laboratory was represented by a r e l a t i v e l y wide range of both temperature and s a l i n i t y . F i n a l l y , comparison of zones 3 and B demon-strated that i n Indian Arm E. p a c i f i c a does not enter a wide range of temperatures and s a l i n i t i e s , but i n the laboratory specimens migrated into s i m i l a r ranges to these and into gradients much steeper than those encountered i n the f i e l d (p. 92 ), and although the number of migrations decreased, they did not cease e n t i r e l y . 115 VERTICAL MIGRATION OF EUPHAUSIA PACIFICA IN "HOME" AND 'FOREIGN" WATERS: EXPERIMENTAL OBSERVATIONS Because previous r e s u l t s indicated that E. p a c i f i c a from Indian Arm migrated more f r e e l y i n a s a l i n i t y structure composed of Indian Arm ( i . e . , "home") water than i n similar structures composed of "foreign" waters (Fig. 124), an additional series of tests was c a r r i e d out to te s t the prem-ise that t h i s species may be reacting to water properties other than temperature and s a l i n i t y . V e r t i c a l migration of E. p a c i f i c a from Indian Arm and from Juan de Fuca S t r a i t was observed i n : a. columns of "home" water with no s a l i n i t y decrease towards the surface (these situations were used as cont r o l s ) , b. columns of "home" water i n which a small decrease i n s a l i n i t y separated upper from lower parts of the column, c. columns containing "home" water i n the lower part and "foreign" water i n the upper part, separated by a small decrease i n s a l i n i t y . While specimens migrated towards the surface of the columns i n a l l l i g h t i n t e n s i t i e s (100-W and 6-W lamps and i n d i r e c t room illumination) i n a series of te s t s , the number of migrations was greater i n the column with the 100-W lamp (Figs. 139 and 140). This may be related to procedures 116 whereby the tests were commenced 24 hours aft e r capture of the animals, and during t h i s period the specimens were kept i n darkness i n the isothermal coolers and i n the incubator. This would i n f e r that the specimens were most active when the change i n l i g h t was the greatest,for example, from dark-ness to an inte n s i t y of 100-W. Results of the tests on the v e r t i c a l migration of Ji* p a c i f i c a , c o l l e c t e d i n Indian Arm and migrating i n Indian Arm ("home") and Juan de Fuca S t r a i t ("foreign") waters are presented i n F i g . 139, i n which open c i r c l e designate the positions to which animals migrated. Migra-t i o n i n "home" water with no s a l i n i t y decrease (column a, control) i s shown to be s i m i l a r to that i n a column of "home" water with a s a l i n i t y decrease of 1.32 °/oo (column b) separating lower and upper parts. Only 3 of 27 migra-tions (11.1 °/oo) stopped i n or below the s a l i n i t y decrease i n column b. However, i n column c, 15 of 30 (50 %) of the v e r t i c a l migrations did not extend above the t r a n s i t i o n zone between the "home" and "foreign" waters between which there was a s a l i n i t y decrease of only 1.07 °/oo. Thus v e r t i c a l migration into the upper part of the columns was subs t a n t i a l l y decreased when the water there was "foreign" instead of "home" water, even when the s a l i n i t y decrease i n column c was less than i n column b and, therefore, less of a potential b a r r i e r to v e r t i c a l migration. Similar tests were c a r r i e d out using specimens of jE. p a c i f i c a c o l l e c t e d i n Juan de Fuca S t r a i t and migrating into water from there ("home" water) and from Indian Arm ("foreign" water). Results are presented i n F i g . 140. Column a i s Juan de Fuca water with no s a l i n i t y decrease (control); column b i s Juan de Fuca water with a zone i n which s a l i n i t y decreases by 0.94 °/oo ; and column c con-s i s t s of Juan de Fuca water i n the lower part separated from Indian Arm water by a t r a n s i t i o n zone with a s a l i n i t y decrease of 0.26 °/oo. In the control, 5 of 36 (13.9 °/oo) migrations did not extend above depths between 22 and 18 cm, the depth of the s a l i n i t y decrease i n column b. In column b, however, 8 of 29 migrations (27.6 °/oo) ended i n or below t h i s p o s i t i o n . I t appears, therefore, that migrations were being r e s t r i c t e d to some extent i n the presence of the small s a l i n i t y decrease (0.94 °/oo) i n "home" water. Never-theless, i n column c, 17 of 31 migrations (54.8 °/oo) did not extend above the transition^zone between "home" and "foreign" waters ( s a l i n i t y decrease was only 0.26 °/oo). Here again the res u l t s indicate that E. p a c i f i c a from Juan de Fuca S t r a i t entered less f r e e l y into "foreign" than into i t s "home" water. Bearing on t h i s , i s the procedure whereby the d i l u t i o n with d i s t i l l e d water of "home" water (from 32.8 °/oo to 25.12 °/oo) i n the upper part of column b was sub s t a n t i a l l y greater than that (from 26.9 °/oo to 25.8°/oo) of the "foreign" water i n the upper part of column c (Fig. 140). From t h i s , i t appears that the use of an increased volume of d i s t i l l e d water as a diluent for "home" water, over that used for "foreign" water, did not influence the 118 specimens'preference for "home" water (p. 94 ). In both series of tests specimens migrated into t h e i r "home" water i n greater numbers than into the "foreign" water. As temperature was constant, and as s a l i n i t y changes were minimal and well within the "tolerances" for E. p a c i f i c a already shown from f i e l d and laboratory r e s u l t s , t h i s difference can be attributed to specimens showing a preference for that water from which they were col l e c t e d , i . e . , t h e i r "home" water, and reacting against the "foreign" water. 119 SURVIVAL OF EUPHAUSIA PACIFICA IN THE LABORATORY IN DILUTIONS OF INDIAN ARM WATER Previous tests of _E. p a c i f i c a i n s a l i n i t y structures i n the laboratory have indicated that water of s a l i n i t y as low as 8.5 °/oo may be occupied temporarily by some speci-mens during t h e i r v e r t i c a l migrations (Fig. 133, Table 6 ) . It was desirable to determine whether specimens could i n fact survive i n such low s a l i n i t y , or i f not, then at what d i l u t i o n s of seawater did lowering the s a l i n i t y a f f e c t sur-v i v a l . This l a t t e r consideration was pre-requisite to sub-sequent tests of the survival of E. p a c i f i c a i n "home" and "foreign" waters. In the f i r s t t e s t 10 specimens were placed i n a control, (26.9 °/oo) of Indian Arm water and i n the water to be dilu t e d , and i n the second test, 17 specimens were s i m i l a r l y treated. The re s u l t s presented i n F i g . 141 i n d i -cate that at s a l i n i t i e s below 22.9 °/oo there was a pro-gressive decrease i n survival over that i n the co n t r o l . The resu l t s of the second t e s t (Fig. 142) indicate a progressive decrease i n survival at s a l i n i t i e s below 24.2 °/oo; however, the percentage survival did not f a l l below that for the con-t r o l u n t i l the water had been d i l u t e d to 18.9 °/oo. In general these tests indicated that E. p a c i f i c a would survive reasonably well i n water with a minimal s a l i n -i t y of approximately 23 - 24 °/oo for periods of at l e a s t two days. A comparison of t h i s s a l i n i t y range with those -- 120 used i n the migration tests (Table 6), indicates that while specimens may be capable of migrating into water with s a l -i n i t i e s as low as 8.5 °/oo, they were not able to survive i n low - s a l i n i t y water when placed i n such conditions for exten-ded periods. On the other hand, the minimal range for high su r v i v a l i n the laboratory was comparable with the minimal s a l i n i t y (23.5 °/oo) at which maximal numbers of E. p a c i f i c a were c o l l e c t e d i n Indian Arm (p. 112 ) and with the minimal s a l i n i t y of water (approximately 21.3 °/oo) i n which migra-t i o n was unrestricted i n s a l i n i t y structures with near-constant temperature (Table 6) i n the laboratory. SURVIVAL OF EUPHAUSIA PACIFICA IN THE LABORATORY IN "HOME" AND "FOREIGN" WATERS The results presented i n Figs. 143 - 147 and summar-ized i n Tables 8, 9 and 10 derive from tests of survival i n the laboratory of E. p a c i f i c a i n "home" and i n "foreign" waters i n conditions of constant temperature and simi l a r s a l i n i t i e s . a. Survival i n "home" water (Indian Arm) and i n waters  from S t r a i t of Georgia, Juan de Fuca S t r a i t and  Malaspina S t r a i t . Figures 143 - 145 present the percentage survival of specimens of E. p a c i f i c a c o l l e c t e d i n Indian Arm and placed i n f i l t e r e d "home" and "foreign" waters. Results are sum-marized i n Table 8; they are tabulated either as the percent-age surviving at the end of the test, or as the duration of 121 the test when there was no s u r v i v a l . A general feature was that larger numbers of specimens of E. p a c i f i c a from Indian Arm survived for longer periods i n t h e i r "home" water (con-t r o l ) than i n waters from the S t r a i t of Georgia, Juan de Fuca S t r a i t and Malaspina S t r a i t ; values ranged from 57 % to 100 % at termination of the several tests (33 to 52 days) i n "home" water. Survival i n "foreign" waters, and i n mixtures of "home" and "foreign" waters, varied from n i l to 50 % at t e r -mination of the various tests (3 to 47 days) (Table 8). In one of a series of two tests (Fig. 143 b and Table 8) survival was 100 % after 43 days i n Indian Arm ("home") water, 50 % af t e r 43 days i n S t r a i t of Georgia water and n i l afte r 9 days i n water from Juan de Fuca S t r a i t . In the other (Fig. 144 a and Table 8) the su r v i v a l , a f t e r 47 days, was 60 % i n Indian Arm water, 30 % i n S t r a i t of Georgia water and n i l i n water from Juan de Fuca S t r a i t . These res u l t s suggest a "preferential sequence" for survival of Indian Arm' J-Strait of Georgia)- Juan de Fuca S t r a i t waters. Thus there appears to be a rel a t i o n s h i p of decreasing sur-v i v a l with increasing distance between the locations of the "home" (Indian Arm) and the "foreign" waters (see F i g . l b for geographical l o c a t i o n of various waters). In another series of tests, c a r r i e d out between June 16 and August 6, 1965 (Fig. 143 a), survival of specimens from Indian Arm was 80 % a f t e r 52 days i n the "home" water, 50 % after 42 days i n water from Juan de Fuca S t r a i t and n i l a f t e r only 9 days i n S t r a i t of Georgia water (Table 8). 122 These results indicated a "preferential sequence" of Indian Arm >Juan de Fuca Strait)- S t r a i t of Georgia water. In a t h i r d series, water from Malaspina S t r a i t (Fig.lb) was substituted for that from the more cent r a l l y - l o c a t e d area i n the S t r a i t of Georgia. Survival (Fig. 144 b; Table 8) ranged from 60 % aft e r 33 days i n "home" water from Indian Arm, 10 % a f t e r 33 days i n water from Juan de Fuca s t r a i t , and n i l a f t e r only 6 days i n water from Malaspina S t r a i t . In t h i s series, therefore, the "preferential sequence" for E. p a c i f i c a from Indian Arm was Indian Arm )- Juan de Fuca S t r a i t )- Malaspina S t r a i t water. The survival of E. p a c i f i c a from Indian Arm was tested i n "home" water, i n d i l u t e d (26.6 °/oo) and undiluted (33.1 °/oo) waters from Juan de Fuca S t r a i t and i n a mixture of equal parts of water from Indian Arm and Juan de Fuca S t r a i t . The re s u l t s (Fig. 145 a; Table 8), a f t e r 47 days, was 57 % survival i n water from Indian Arm, 13 % i n the d i l u t e d water from Juan de Fuca S t r a i t , and n i l i n the undilu-ted water from Juan de Fuca S t r a i t . Survival was n i l i n the mixture of Indian Arm and Juan de Fuca S t r a i t waters and, as well, the rate at which specimens died was highest. A com-parison of the curves of survival (Fig. 145 a) of E. p a c i f i c a from Indian Arm i n the di l u t e d and undiluted waters from Juan de Fuca S t r a i t , indicates l i t t l e or no difference attributable to the use of d i s t i l l e d water as a diluent or to the higher s a l i n i t y , even though s a l i n i t i e s i n Indian Arm have not been observed to exceed approximately 27.4 °/oo. 123 In a series of tests of Indian Arm specimens i n mixtures of waters from Indian Arm and Malaspina S t r a i t , s u r v i v a l (Fig. 145 ta; Table 8) was 57 % a f t e r 47 days i n Indian Arm water, n i l to 10 % after 6 to 37 days i n the various mixtures of waters, and n i l a f t e r 3 days i n water e n t i r e l y from Malaspina S t r a i t . Comparison of the survival curves demonstrated that E. p a c i f i c a from Indian Arm sur-vived i n larger numbers and for longer periods i n the "pref-e r e n t i a l sequence" of Indian Arm water )- a mixture contain-ing 25 % of water from Malaspina S t r a i t )- 33 % Malaspina S t r a i t water )- 50 % Malaspina S t r a i t water )- 100 % Malas-pina. S t r a i t water. Thus with an increasing proportion of water from Malaspina S t r a i t , survival of specimens from Indian Arm was progressively lowered. b. Survival i n "home" water (Juan de Fuca S t r a i t ) and i n  waters from S t r a i t of Georgia and Indian Arm. A second procedure was adopted i n order to determine whether specimens from a d i f f e r e n t "home" water (from Juan de Fuca S t r a i t ) reacted i n "preferential sequences" equiva-lent to those of the Indian Arm specimens. Accordingly the survival of specimens of E. p a c i f i c a c o l l e c t e d i n Juan de Fuca S t r a i t was tested i n f i l t e r e d seawater from Juan de Fuca S t r a i t ("home" water), the S t r a i t of Georgia and Indian Arm. Results are summarized i n F i g . 146 a, b, and Table 9. Survival i n one test (Fig. 146 a; Table 9) l a s t i n g 43 days was 100 % i n di l u t e d (26.5 °/oo s a l i n i t y ) and 80 % i n 124 undiluted (32.8 °/oo) "home" water; 80 % i n water from Indian Arm, and 50 % i n water from the S t r a i t of Georgia. In a second t e s t (Fig. 146 b; Table 9) su r v i v a l , a f t e r 31 days, was 60 % i n the "home" water d i l u t e d to 26.8 °/oo, 30 % i n water from Indian Arm and 20 % i n water from the S t r a i t of Georgia. From the res u l t s of these two tests i t appears that there was a "prefe r e n t i a l sequence" i n the survival of JE. p a c i f i c a from Juan de Fuca S t r a i t i n the order : Juan de Fuca S t r a i t )- Indian Arm )~ S t r a i t of Georgia. Although s a l i n i t i e s i n Juan de Fuca S t r a i t range from 31 to 34 °/oo, survival of Ji* P a c i f i c a (Fig. 146 a, Table 9) from there was greater i n di l u t e d (26.5 °/oo) than i n undiluted (32.8 °/oo) waters from the S t r a i t . This suggests the absence of any harmful e f f e c t s a t t r i b u t a b l e to a decrease i n s a l i n i t y (below that encount-ered i n the f i e l d ) or to the use of d i s t i l l e d water as a diluent i n the laboratory t e s t s . c. Survival i n "home" water ( S t r a i t of Georgia) and i n  water from Indian Arm. Figure 147 and Table 10 present the percentage sur-v i v a l of specimens of E. p a c i f i c a c o l l e c t e d i n the S t r a i t of Georgia and placed i n seawater from S t r a i t of Georgia and Indian Arm. A general feature was the s i m i l a r i t y i n sur-v i v a l of the species i n the two waters. There was n i l sur-v i v a l (Fig. 147 a); afte r 34 days i n water from the S t r a i t of Georgia and a f t e r 37 days i n water from Indian Arm. Results presented i n F i g . 147 b show a su r v i v a l , a f t e r 37 days-, of 50 % i n water from the S t r a i t of Georgia, and 40%,;i»ewate.©.: from Indian Arm. In these tests the survival of specimens.." from the S t r a i t of Georgia i n t h e i r "home" water was lower than i n the equivalent tests of the survival of E. p a c i f i c a from Indian Arm and Juan de Fuca S t r a i t i n t h e i r "home" waters 126 DISCUSSION OF SURVIVAL IN THE LABORATORY In the tests of survival of Euphausia pacifica,the "home" and "foreign" waters were subjected to the same con-di t i o n s of darkness, concentration of specimens, additions of food, pH and oxygen content. P a r t i c u l a r attention was given to eliminating any but minor differences i n s a l i n i t y among the samples and temperature was constant at 10°C which was si m i l a r to that at the locations and depths at which specimens were c o l l e c t e d i n the f i e l d . Tests with E. p a c i f i c a from Indian Arm indicated that survival was sim i l a r i n di l u t e d (26.5 °/oo) and undiluted (33.1 °/oo) water from Juan de Fuca S t r a i t , although s a l i n i t i e s i n Indian Arm were not observed to exceed approximately 27.4 °/oo. In a second te s t survival of specimens from Juan de Fuca S t r a i t was s l i g h t l y greater i n d i l u t e d (26.5 °/oo) than i n undiluted (32.8 °/oo) water from Juan de Fuca S t r a i t , although s a l i n i t i e s there ranged from approximately 31 - 34 °/oo. Thus, there was no decrease i n the survival i n s a l i n i t i e s which d i f f e r e d s u b s t a n t i a l l y from those encountered i n the f i e l d . Another important point i n the above i s the absence of any harmful e f f e c t s a t t r i b u t -able to the use of d i s t i l l e d water as a diluent (p. 94 ).. Although E_. p a c i f i c a survived comparatively well over a wide range of s a l i n i t i e s (23 or 24 to 33.1 °/oo) i n the laboratory, nevertheless, i n order to remove differences i n s a l i n i t y as a possible factor i n the survival of specimens 127 i n "home" and "foreign" waters, s a l i n i t i e s of waters used were adjusted to sim i l a r values (a t o t a l range of 26.3 -26.9 °/oo). The experiments with E. p a c i f i c a demonstrated that, i n general, specimens survived better i n t h e i r "home" waters than i n "foreign" waters, or i n mixtures of these waters. I t i s suggested that such differences resulted from the i n f l u -ence of environmental factors other than temperature and s a l i n i t y which, i n some way are associated with the "home" and "foreign" waters. Bary (1963 a, 1964) developed the premise that d i f f e r e n t water bodies contain factors that are i n some sense unique, the "unique properties", and that each species (or the population of a species i n the present study) reacts to these properties i n an ind i v i d u a l manner. On t h i s basis, the survival of E. p a c i f i c a i n the laboratory requires to be considered i n r e l a t i o n t o j f i r s t l y , an oceanographic factor - the unique properties of waters c o l l e c t e d from several locations; and secondly, a b i o l o g i c a l factor - the reactions of specimens c o l l e c t e d at d i f f e r e n t locations to these properties. I t follows that survival of E. p a c i f i c a would be dependent on the tolerance of specimens towards the unique properties of waters c o l l e c t e d at d i f f e r e n t geograph-i c a l l o cations. The s u r v i v a l of E. p a c i f i c a from Indian Arm indicated that specimens were considerably more tolerant towards "home" water than towards "foreign" waters. The comparatively poor survival i n "foreign" waters may have resulted from a d e f i c -iency i n these waters of some essential property or properties 128 present i n the "home" water, or (and perhaps as well as) that other properties present i n the "foreign" waters were i n some way deleterious to s u r v i v a l . Although the nature of these properties i s unknown,the preference for "home" over "foreign" waters was a consistent feature i n a l l t ests, over a one-year period. For p a r t i c u l a r waters, there were fluctuations i n s u r v i v a l . For example, i n Juan de Fuca S t r a i t water survival ranged from n i l to 50 % over periods varying from 9 to 47 days; and even i n "home" water, sur-v i v a l ranged from 52 to 100 % over 33 to 57 days. These fluctuations were obtained i n experimental conditions that were s i m i l a r for a l l tests and were c l o s e l y c o n t r o l l e d . They indicate, therefore, that the properties of "home" and "foreign"water a f f e c t i n g survival probably were being modified, thereby influencing the reaction of specimens. Not only were there fluctuations i n survival within a water from a p a r t i c u l a r l o c a t i o n , but the r e l a t i v e merits of a series of waters varied from time to time. This was indicated by changes i n the "preferential sequence" i n the survival of specimens. In one sequence, specimens from Indian Arm survived best i n water from Indian Arm, less so for water from the S t r a i t of Georgia, and lea s t for water from Juan de Fuca S t r a i t (tests of December 9, 1965 - Janu-ary 20, 1966, and January 26 - March 14, 1966), but t h i s changed to survival being best i n water from Indian Arm, less so i n water from Juan de Fuca S t r a i t and lea s t i n S t r a i t of Georgia water (test of June 16 - August 6, 1965). The 129 f i r s t sequence suggests that survival decreased with increas-ing (geographical) distance between the locations of the "home" and the "foreign" waters( F i g . l b ) . This leads to the speculation that Indian Arm water included a property es s e n t i a l to the survival of E. p a c i f i c a from Indian Arm, and that specimens became increasingly adversely affected by some change (perhaps i n the concentration of the property) i n the "foreign" waters, the further these were from the "home" water. The reversal i n the second sequence of the "foreign" waters may have been influenced by the use of u n f i l t e r e d seawater i n the survival tests of June 16 - August 6, 1965. Survival was poor ( n i l a f t e r 9 days) i n u n f i l t e r e d water from the S t r a i t of Georgia when compared with that (30' to 50 % over 43 - 47 days) for f i l t e r e d water from the same lo c a t i o n i n the tests of December, 1965 to March, 1966. Alternativelyjrunoff i s maximal during l a t e June to mid-July and the S t r a i t of Georgia water used i n the survival tests was c o l l e c t e d i n the central part of the Strait,which i s strongly influenced by the discharge of the Fraser River. This runoff, although generally regarded as a f f e c t i n g the surface and near-surface waters, could possibly have caused fluctuations i n the properties of water at 100 m and have contributed to the poor su r v i v a l of specimens c o l l e c t e d i n June, 1965. Some support for t h i s a l t e r n a t i v e i s given by Waldichuk (1957) who describes the deep water which flows into the basin of the S t r a i t of Georgia as being not a "pure" water but rather a mixture of seawater and Fraser River water 130 of a c e r t a i n age. It i s possible therefore, that the i n f l u -ence of S t r a i t of Georgia water on the survival of specimens may be modified, (perhaps f a i r l y rapidly) through mixing with Fraser River water. If the lower survival of E. p a c i f i c a i n "foreign" waters could be attributed to a deficiency of esse n t i a l properties and/or the presence of deleterious properties, then i t would be of int e r e s t to observe whether the addition of "home" water to i t would improve s u r v i v a l . Survival of specimens from Indian Arm i n waters from Indian Arm, Malas-pina S t r a i t and mixtures of the twojindicated, f i r s t l y , a better survival i n "home" than i n "foreign" water, and, secondly, increases i n sur v i v a l i n mixtures i n which the proportion of "home" water was progressively increased'. Presumably, any deficiency of essential properties and/or properties deleterious to sur v i v a l i n Malaspina S t r a i t water were a l l e v i a t e d , at lea s t to some extent, through mixture with "home" water. However, even at the greatest d i l u t i o n of Malaspina S t r a i t water with Indian Arm water, the sur-v i v a l of E. p a c i f i c a indicated that specimens were consider-ably less "tolerant" towards the mixture than to the "pure" Indian Arm water and that considerably more "home" water than "foreign" water would be required i n a mixture of the two i n order to approach the survival of specimens i n water of e n t i r e l y "home" o r i g i n . Why Malaspina S t r a i t water should contribute to the poor survival ( n i l a f t e r 3 - 6 days) of specimens from 131 Indian Arm i s unknown. The l o c a t i o n (off the mouth of Je r v i s Inlet) and the r e l a t i v e l y shallow depth (50 m) from which water was c o l l e c t e d i n Malaspina S t r a i t may be implicated. This area receives the combined influence of runoff from the northern i n l e t s and the Fraser River (Waldichuk, 1957) which presumably, could have modified some property or properties e s s e n t i a l to, or perhaps introduced some property or proper-t i e s detrimental to, the survival of the specimens from Indian Arm. Survival of E. p a c i f i c a from Indian Arm indicated that specimens were considerably more tolerant of "home" water than of water from Juan de Fuca S t r a i t or of a 1:1 mixture of the two waters. Apparently, the low tolerance of specimens from a coastal i n l e t towards an "oceanic-coastal" water, such as c o l l e c t e d i n Juan de Fuca S t r a i t , persisted with the introduction of "home" water, at le a s t i n the 1:1 mixture. The survival of E. p a c i f i c a from Juan de Fuca S t r a i t demonstrated, as with specimens from Indian Arm, a greater tolerance towards "home" water than towards "foreign" waters. Survival i n the "foreign" waters further demonstrated, how-ever, that specimens from Juan de Fuca S t r a i t were more tolerant of Indian Arm water (30 to 80 % s u r v i v a l , over 31 - 43 days) than were specimens from Indian Arm (p.128 ) of water from Juan de Fuca S t r a i t ( n i l to 50 % sur v i v a l , over 9 - 4 7 days). In other words specimens from an "oceanic-coastal" population of E. p a c i f i c a as c o l l e c t e d i n Juan de Fuca S t r a i t , were more tolerant towards i n l e t water than were specimens of an i n l e t population of the same species towards "oceanic-coastal" water. The survival of specimens from Juan de Fuca S t r a i t and Indian Arm was s i m i l a r i n S t r a i t of Georgia water, although su b s t a n t i a l l y below that observed i n "home" waters. Survival i n water from the S t r a i t of Georgia ranged from 20 to 50 %, over 31 - 43 days for specimens from Juan de Fuca S t r a i t , and 30 - 50 %, over 43 -47 days, for specimens from Indian Arm.. (The one exception to t h i s was the abrupt decrease i n sur-v i v a l ( n i l a f t e r 9 days) of specimens from Indian Arm i n u n f i l t e r e d water from the S t r a i t of Georgia during June,1965). From the above i t might be infe r r e d that E. p a c i f i c a c o l l e c t e d from "oceanic-coastal" and i n l e t waters have a low but a sim i l a r degree of tolerance towards S t r a i t of Georgia water. In contrast to E. p a c i f i c a from Indian Arm and Juan de Fucajstrait, the survival of specimens from the S t r a i t of Georgia was comparatively low, and also s i m i l a r , i n both "home" and "foreign" waters. It must be emphasized, however, that there were only a few tests and that these were made using u n f i l t e r e d water. Survival ranged from 0 to 50 %,over 34 £ 37 days i n S t r a i t of Georgia water, and from 0 to 40 %, over the same period, i n water from Indian Arm. This suggests that the specimens were "tolerant" to a si m i l a r degree towards both waters. The survival of E. p a c i f i c a from the S t r a i t of Georgia demonstrated that specimens were more tolerant of Indian Arm 133 water ( n i l to 40 % s u r v i v a l , over 34 - 37 days, i n u n f i l t e r e d water) than were specimens from Indian Arm towards water from the S t r a i t of Georgia ( n i l survival a f t e r 9 days, i n u n f i l -tered water). On t h i s basis specimens of a "coastal" popu-l a t i o n of E. p a c i f i c a , such as c o l l e c t e d i n the S t r a i t of Georgia, appear to have been more tolerant of i n l e t water than were specimens of an i n l e t population of the same species towards "coastal" water. This s i t u a t i o n i s s i m i l a r to that discussed e a r l i e r (p. 131) for specimens from Juan de Fuca S t r a i t . 134 VIII. DISCUSSION The ranges of temperature and s a l i n i t y i n Indian Arm during the period from January, 1960, to July-August, 1961, have been shown i n temperature-salinity (T-S) diagrams. These diagrams and geographical d i s t r i b u t i o n s of tempera-ture, s a l i n i t y and density (O-t) also show that within these ranges, conditions fluctuated seasonally and were periodic-a l l y disrupted by intrusions of outside water from the S t r a i t of Georgia through Burrard Inlet (see discussion pp. 29-33 ). Temperature-salinity-plankton (T-S-P) diagrams and geographical d i s t r i b u t i o n s of euphausiids have been used to indicate t h e i r occurrences and reactions to t h e i r environ-ment, and changes i n i t , of the adults of four species (Euphausia p a c i f i c a , Thysanoessa s p i n i f e r a , Thysanoessa  longipes and Thysanoessa r a s c h i i ) and the developmental stages of E_. p a c i f i c a . The occurrences of large numbers of adult specimens of E_. p a c i f i c a i n a wide range of d i s t r i b u -t i o n and i n a l l months i n Indian Arm, coupled with the presence of a complete developmental Sequence, indicated that t h i s species was resident i n the i n l e t and as such was tolerant to a high degree towards the properties, i n par-t i c u l a r temperature and s a l i n i t y , of i n l e t waters. On the other hand, the occurrences (often sporadic), of r e l a t i v e l y small numbers and i n l i m i t e d d i s t r i b u t i o n s of adult speci-mens of T. spinfera, T # longipes and T. r a s c h i i , and the 135 absence of most or a l l of the developmental stages of these species, indicated that they were expatriates i n Indian Arm. This, together with t h e i r usually rapid disappearance from the i n l e t suggests they were considerably less tolerant of the properties of i n l e t water than E. p a c i f i c a . Wide variations i n d i s t r i b u t i o n , and perhaps t o l e r -ances to temperature and s a l i n i t y , occurred not only among the four species, but also within the one developmental sequence studied, that of E. p a c i f i c a . The e a r l i e r develop-mental stages (the f i r s t and second nauplius stages and the metanauplius stage) were markedly r e s t r i c t e d i n t h e i r d i s -t r i b u t i o n s to deeper waters, within a r e l a t i v e l y narrow range of temperature and s a l i n i t y , when compared with the eggs, l a t e r developmental stages (calyptopii and f u r c i l i a ) and the adults (see discussion pp.55-57 ). These accord, i n general terms, with results from other workers who have reported that a species may occur at a ce r t a i n depth when adult, but while young i t may have a d i f f e r e n t v e r t i c a l d i s t r i b u t i o n . In p a r t i c u l a r , Fraser (1936) reported that whereas eggs, n a u p l i i and metanauplii of Euphausia superba were found at deep l e v e l s , the l a t e r developmental stages (calyptopii and f u r c i l i a ) migrated to shallower depths. In a previous study i n Indian Arm (Shan, 1962) adult copepods were found at depths d i f f e r e n t from those of the develop-mental stages. It has been suggested i n reviews by Kinne (1963, 1964) that the range of temperature and s a l i n i t y tolerance, and thereby d i s t r i b u t i o n , may be narrower during 136 early development. Although the occurrences and d i s t r i b u t i o n of the various species and developmental stages were related by temperature and s a l i n i t y (Tables 4 and 5) to environmen-t a l conditions i n Indian Arm, there was a question as to whether the temperatures and s a l i n i t i e s were the "regula-tory" factors c o n t r o l l i n g the d i s t r i b u t i o n s , or whether other, as yet undetermined, properties, and the reactions of specimens towards these, were operative (see discussions: E. p a c i f i c a (pp.45 - 46),T. s p i n i f e r a (p. 65a ) ,T. longipes (pp.71- 73 )and T. r a s c h i i (pp.77 - 78 ). There are indications that temperature and s a l i n i t y may be, at le a s t i n part, regulatory factors p a r t i c u l a r l y i n the highly modified waters between about 10 m and the sur-face. The f i r s t indications were that the rapid changes i n temperature and s a l i n i t y appeared to r e s t r i c t the v e r t i c a l migration of E_. p a c i f i c a into these near-surface waters. This species i s widely d i s t r i b u t e d i n t r a n s i t i o n a l water at intermediate depths and i n deeper waters and did not appear to be influenced by the ranges and fluctuations of tempera-ture and s a l i n i t y i n these waters. On the other hand, the occasional occurrences of small numbers i n , or more usually the complete absence of specimens from, surface waters appeared to r e s u l t l a r g e l y from t h e i r reactions towards the zone of maximum change i n the temperature and s a l i n i t y ( i . e . , the thermocline and halocline) c h a r a c t e r i s t i c of the upper waters. During December-April, i n periods of seasonal cooling 137 isothermal (but not isohaline) conditions prevailed and small numbers of E. p a c i f i c a were c o l l e c t e d i n surface waters i n which minimal temperatures and s a l i n i t i e s were as low as 5.3°C and 7.0 °/oo. Between June and October, during the period of seasonal warming, the temperature of upper waters <&ss'.• upi to.. 20.2°C and s a l i n i t y was low; both the halocline and thermo-c l i n e , were present. Specimens did not occur i n the upper waters i n these conditions. These data suggested there was more influence on migration when temperature and s a l i n i t y changes were pronounced and occurred together. The results of that portion of the laboratory study concerned with the migration of E. p a c i f i c a i n temperature, s a l i n i t y and combined temperature-salinity structures demon-strated relationships s i m i l a r to those i n the f i e l d . In conditions simulating those of thermocline and h a l o c l i n e i n the f i e l d the numbers migrating decreased as the temperature increased or s a l i n i t y decreased towards the surface; the e f f e c t s were more pronounced when the rate of change of temperature (pp. 107 - 108 ) or s a l i n i t y (p. 103 ) was great-est and when temperature and s a l i n i t y structures were com-bined (for discussion, see pp.111 - 112 ),Although there appeared to be some agreement between f i e l d and laboratory findings i n the effects of thermoclines and haloclines on JE. pacifica,occurrences i n r e l a t i o n to temperature and s a l i n i t y i n the f i e l d suggested that reactions of specimens towards temperature and s a l i n i t y were stronger than i n the laboratory (pp.113 - 114 )despite the much steeper gradients 138 obtained i n the laboratory (p. 92 ). The f i e l d studies indicate that, except on rare occasions, the expatriate species were not c o l l e c t e d either i n the surface water (T. spinifera) or above 30 m ( T. r a s c h i i ) and 60 m (T. longipes). I t i s possible these d i s t r i b u t i o n s may be related, at l e a s t i n part, to the large fluctuations i n the temperature and s a l i n i t y of upper waters. The very few tests i n the laboratory of the migra-t i o n of T. s p i n i f e r a and T. longipes suggested, however, that these species may be considerably more tolerant of high temperatures and low s a l i n i t i e s than the f i e l d studies indicated. For example, a few specimens of T. s p i n i f e r a migrated i n the laboratory into waters with a maximal tem-perature of 25.0°C and a minimal s a l i n i t y of 17.8 °/oo, whereas i n Indian Arm, with only two exceptions over two years, the maximum temperature at which T. s p i n i f e r a was c o l l e c t e d was 13.7°C and the minimal s a l i n i t y was 23.7 °/oo, S i m i l a r l y , specimens of T. longipes migrated i n the labora-tory into waters with a minimal s a l i n i t y of 15.0 °/oo, but i n Indian Arm were c o l l e c t e d at the minimal s a l i n i t y of 24.5 °/oo. It appears, therefore, that i n general there was a more l i m i t e d d i s t r i b u t i o n of E. p a c i f i c a , T. s p i n i f e r a and T. longipes with respect to changes i n temperature and s a l i n i t y i n the upper waters i n Indian Arm than temperature and s a l i n i t y structures i n the laboratory would indicate was fea s i b l e ; and t h i s , despite the steeper gradients used 139 i n the laboratory. An inference to be drawn i s that other environmental properties, as yet undetermined, were super-imposed upon those of temperature and s a l i n i t y and were exerting an influence on the d i s t r i b u t i o n of these species i n Indian Arm. A possible explanation i s that the d i s p a r i t y between the d i s t r i b u t i o n s as observed i n the f i e l d , and the potential d i s t r i b u t i o n s suggested by laboratory findings may l i e i n the d i f f e r e n t properties of natural fresh waters and d i s t i l l e d water, and i n the processes ensuing on d i l u t i o n of seawater i n natural conditions. D i l u t i o n of upper waters i n Indian Arm i s predominantly by freshwater runoff at the surface and subsequent entrainment and mixing between t h i s and saline waters immediately below. In contrast, i n the laboratory, d i s t i l l e d water was used as a diluent for seawater, which was c o l l e c t e d consistently from one, deep source (75m) i n Indian Arm and which probably was r e l a t i v e l y free from the d i l u t i o n processes present i n the upper waters. Although the tempera-ture and s a l i n i t y of t h i s deep water was adjusted i n the laboratory to simulate conditions i n "natural" upper waters, i t may have been quite d i f f e r e n t i n other properties with the r e s u l t that reactions of specimens d i f f e r e d from those i n the f i e l d . In general, occurrences of the expatriate species i n Indian Arm were associated with the inflow (from various causes) of outside waters into the i n l e t . In these situations, T. s p i n i f e r a (p. 64 ) a n < ^ Z « longipes (p. 71 ) occurred i n maximal numbers and usually towards the mouth of the i n l e t . When the influence of outside waters was decreasing through mixing with resident water or was not apparent, these species decreased i n abundance and were often absent from c o l l e c t i o n s . On the other hand, the resident species, E. p a c i f i c a , decreased i n numbers and/or s h i f t e d i n d i s t r i b u -t i o n i n a d i r e c t i o n removed from the influence of outside waters entering Indian Arm (pp. 44 - 45 ). During periods when oceanographic conditions were r e l a t i v e l y stable i n the i n l e t , with no detectable inflow of outside waters, E. pac- i f i c a increased i n abundance and became more or less evenly d i s t r i b u t e d throughout waters at intermediate and deeper l e v e l s . The sporadic occurrences i n Indian Arm of T. r a s c h i i , another expatriate species, were not associated with detec-table movements of outside water into the i n l e t . Thus the means of transport associated with the entry of the other expatriate species into Indian Arm either were not apparent or were reduced for the periods i n which T. r a s c h i i entered. The implications of t h i s are discussed on pp.75 - 76 ). The s h o r t - l i v e d occurrences of t h i s species, and i t s narrow range of d i s t r i b u t i o n on occasions when i t was present, suggest that t h i s species was reacting against Indian Arm waters. Although the entry of outside waters was detectable for the most part i n the d i s t r i b u t i o n s of temperature and s a l i n i t y of intermediate and deep waters, the changes i n these properties were r e l a t i v e l y minor and well within the range that the d i s t r i b u t i o n s of the various species have shown they were able to tolerate i n Indian Arm. Neverthe-l e s s , these intrusions of outside water often were to be associated with the presence and/or an increase i n the abund ance of expatriate species and i n major fluctuations i n the abundance and/or d i s t r i b u t i o n of the resident species ( E. p a c i f i c a ) i n the i n l e t . It i s believed that the intruding waters transported expatriate species into Indian Arm, and also flushed resident water and species out of the i n l e t and/or altered t h e i r d i s t r i b u t i o n within the i n l e t . For specimens within the i n l e t the above evidence leads to a questioning of the concept that temperature and s a l i n i t y were the primary regulatory factors i n the occur-rences, abundance and d i s t r i b u t i o n s of euphausiids i n i n t e r -mediate and deep waters. It suggests, instead, that other properties associated with intruding and resident waters, and the reactions of specimens to these were more important. The nature of these properties (analagous to the " b i o l o g i c a l differences" between natural sea waters of Wilson et a l . (1951, 1952, 1954), the "unique properties" of Bary (1963a, 1964); and to the seawater " q u a l i t i e s " of Johnston (1962, 1964 ) i s unknown. They may be attributable to: "ectocrines or "external metabolites" released into the water by marine organisms and b e n e f i c i a l or harmful to others of the same or d i f f e r e n t species (Lucas, 1947, 1949; Srinivasagam, 1966), dissolved organic substances acting as growth factors and supplementing the diet ( S h i r a i s h i and Provasoli, 1959.; 142 Johnston, 1962 ), non-living p a r t i c u l a t e material also supplementing the diet (Conover, 1964), the type of food organism i n the water ( Mullin, 1963), dissolved inorganic materials (,Lucas, 1947 ; Lewis, 1967, and unpublished, I n s t i t u t e of Oceanography, University of B r i t i s h Columbia ), or perhaps interactions of organic and inorganic materials such as chelationjof trace metals by naturally occurring dissolved organic substances (Johnston, 1964). Regardless of their*nature, these undetermined pro-perties apparently "regulate" the reactions of specimens and do t h i s , i t would seem, by means of physiological responses to the properties — the species "tolerance". Thus, expat-r i a t e species appear to to l e r a t e the "unique properties" of outside water, as indicated by t h e i r entry into Indian Arm i n association with these waters, but the decrease i n t h e i r numbers and often s h o r t - l i v e d residence which ensued on the mixing between outside and resident Waters indicates; aadegree of intolerance of the "unique properties" of Indian Arm water. properties between the resident and intruding waters and the e f f e c t s on the species must be considered. Essential proper-t i e s present i n intruding water would become d i l u t e d during the process of mixing with the resident water; with s u f f i -cient d i l u t i o n the concentration of such properties could become l i m i t i n g to the expatriate species, r e s u l t i n g i n a decrease i n t h e i r abundance, and eventually i n t h e i r elimina-t i o n from the waters i n the i n l e t . Conversely, an increasing concentration of properties present i n resident water and In order to explain these reactions the i n t e r a c t i o n of 143 deleterious to expatriate species would provide s i m i l a r r e s u l t s . This sort of mechanism may also "explain" the reactions of the resident species (E. p a c i f i c a ) . That E. p a c i f i c a i s resident (and reproduces) i n Indian Arm water means that i t i s "tolerant" of the properties of t h i s water. But that the abundance of E. p a c i f i c a i s reduced and the d i s t r i b u t i o n altered by intruding water shows that some pro-perty of the intruding water, or perhaps the d i l u t i o n of some essen t i a l property of resident water, produces an adverse e f f e c t on specimens. Thus the specimens of a l l species are reacting favourably towards ( i . e . , they tolerate) the "unique properties" or "essential factors" within the water i n which they are resident (the "home" waters) and against ( i . e . , they are intolerant towards) the properties of the water i n which they are not resident. This two-way type of reaction appears to be e s s e n t i a l to an understanding of the occurrences of a l l species of euphausiids i n Indian Arm. This same twos-way reaction helps to understand the v e r t i c a l d i s t r i b u t i o n s of E. p a c i f i c a , T. s p i n i f e r a and Z« longipes i n Indian Arm. From the T-S-P diagrams i t was apparent that from month to month the waters from about 90 to 200 m displayed only small ranges of temperature and s a l i n i t y . For E. p a c i f i c a , these ranges were subsequently shown i n the laboratory tests of migration and survival^not to cause adverse reactions i n t h i s species. Moreover, the temperature and s a l i n i t y of waters below 120 m, from which a l l species were mostly absent, would be closer to the 144 outside waters i n which such species as T_. s p i n i f e r a and T_. longipes are believed to have entered Indian Arm. Accord-ingly, i f only temperature and s a l i n i t y were regulating occurrences these species could be expected to concentrate i n those deeper waters. Such was not the case, with only rare exceptions. Again, i t would appear that a deficiency of some esse n t i a l property or properties or perhaps the presence of some deleterious property or properties i n h i b i t e d d i s t r i b u t i o n into these deep waters. I t i s in t e r e s t i n g to note, however, that nauplius I and II and the metanauplius of E. p a c i f i c a occurred i n the deep waters. Occurrences of Thysanoessa r a s c h i i , between 30 and 60m i n Indian Arm, did not appear to be related to temperature and s a l i n i t y . The waters below 60 m were characterized by r e l a t i v e l y low temperatures and high s a l i n i t i e s , with con-siderably less range of v a r i a t i o n than the water from which UL' r a s c h i i was c o l l e c t e d , and nearer the properties of the outside waters, from which the specimens originated. It would appear, therefore, that the waters below 60 m should have been as suitable (or even more so) as the waters between 30 and 60 m for a species such as T. r a s c h i i which normally inhabits mixtures of oceanic and coastal water. It i s a p o s s i b i l i t y , to judge from i t s occurrences i n a narrow range of geographical d i s t r i b u t i o n i n the i n l e t that the few specimens of T. r a s c h i i which entered did so within the confines of small and undetected volumes of outside water. This water would eventually be dissipated through mixing and d i l u t i o n with the resident waters i n Indian Arm. As with other expatriate species (T. s p i n i f e r a and T. longipes), the d i l u t i o n of essential properties introduced by outside waters and/or the presence of detrimental properties i n the resident water would have contributed to the f a i l u r e of T. r a s c h i i to survive for prolonged periods i n Indian Arm. Euphausia p a c i f i c a occurs commonly i n much of the North P a c i f i c (Brinton, 1962) and also extends, very often i n large numbers, into the most secluded of coastal areas, e.g.,Indian Arm. This sort of d i s t r i b u t i o n i s not common among zooplank-tonic species. It i s presumed to be maintained i n two ways, by recruitment into coastal areas from the oceanic stock, and by specimens becoming more or less permanent, breeding popu-l a t i o n s within p a r t i c u l a r locations. Both means probably apply i n B r i t i s h Columbia coastal waters. The expatriate species enter Indian Arm and there i s no reason to believe the E_. p a c i f i c a does not enter along with them; on the other hand, E. p a c i f i c a undergoes a complete l i f e - h i s t o r y i n Indian Arm whereas the other species apparently do not breed there at a l l , and as already discussed, occur there only spasmodi-c a l l y , i n association with intrusions of outside waters. A large range i n environmental conditions ensues on mixing of oceanic into coastal waters and E. p a c i f i c a occurs throughout t h i s range. It seemed that t h i s single species provided an opportunity to test whether i t s occurrences were related to the changing temperatures and s a l i n i t i e s between oceanic and coastal areas, or whether other properties were involved, and whether specimens became "adapted" to waters such as:found i n Indian Arm. Accordingly, the laboratory series of experiments were c a r r i e d out. Specimens c l e a r l y reacted to changes of temperatures and s a l i n i t y i n the laboratory (Figs. 137 and 138 ) but usually not u n t i l temperatures were higher or s a l i n i t i e s lower than were "usual" i n the species environment; and t h i s , despite the steeper gradients used i n the laboratory. The only natural s i t u a t i o n where such reactions were l i k e l y was i n the thermocline and hal o c l i n e where ranges (but not gradients) comparable to those i n experimental situations were present. Even though these reactions were present, evidence suggested that a response to another condition was superimposed i n the f i e l d . In laboratory experiments i n which specimens of E. p a c i f i c a from one l o c a l i t y and water("home" water) were tested for t h e i r reactions (migration or survival) i n water from another area ("foreign" water) specimens showed notably less adverse reactions i n the "home" than i n the "foreign" water. Migration i n s a l i n i t y structures composed of waters c o l l e c t e d from several geographical locations (p. 102 ) indicated that, while migrations decreased i n low-salinity waters, the specimens "tolerated" approximately 4 - 5 °/oo lower s a l i n i t y . ( F i g . 124) i n Indian Arm water ( i . e . , t h e i r "home" water) than i n i d e n t i c a l s a l i n i t y structures composed of S t r a i t of Georgia and Juan de Fuca waters ( i . e . f o r e i g n " waters). This was the f i r s t i n d i c a t i o n i n the laboratory 147. that i n addition to the reaction of specimens towards decreasing s a l i n i t y , they were also reacting towards some factor(s) associated with other properties of "home" and "foreign" waters. Subsequent tests of migration, i n water columns with nearly constant temperature and small d i f f e r -ences i n s a l i n i t y separating the two waters, further demon-strated that E. p a c i f i c a was considerably more tolerant of the properties of "home" water than of those of "foreign" waters ( Figs. 139, 140 and pp.116 -li-8).Again the influence of properties, other than temperature and s a l i n i t y , appar-ently was (being) instrumental i n determining the v e r t i c a l migration of specimens/;, F i n a l l y , the survival of E. pac- i f i c a c o l l e c t e d from several geographical locations and placed i n various waters under con t r o l l e d conditions demon-strated that populations i n general were more tolerant towards the properties of t h e i r "home" water than towards the "foreign" waters or mixtures of the two. The evidence again suggests, as with the f i e l d studies, that the r e l a -t i v e l y poor survival of specimens i n "foreign" waters, and i n mixtures containing such water, resulted from a d e f i c -iency of some esse n t i a l property or properties or (and perhaps as well as) that some other property or properties were present and were i n some way deleterious to survival (see discussion, pp.127 - 133 ). The evidence from occurrences and reactions of euphausiids i n the f i e l d and from results of experiments, appears to be mutually supporting. From the above i t i s 148 apparent that species do react against gradients of tempera-ture and s a l i n i t y i n the f i e l d , for example by concentrating below structures such as the thermocline and halocline, and i n laboratory experiments. Nevertheless, i n experiments specimens from one water ("home") reacted s i m i l a r l y , but at di f f e r e n t values, to the same gradients of temperature and s a l i n i t y set up i n another water ("foreign"). Euphausia  p a c i f i c a as a resident species i n Indian Arm apparently reacts against and becomes d i s t r i b u t e d at the furthest point away from intruding water that i s associated with the presence of other species (Thysanoessa spp.). None of the four species entered the deeper water of Indian Arm, except very r a r e l y . Neither of these situations was dependent on changes of s a l i n i t y or temperature since the changes i n v o l -ved are in c l u s i v e i n the ranges inhabited by the species i n the f i e l d and were subsequently shown to be well within the ranges "tolerated" by species i n laboratory experiments. The si t u a t i o n has two p a r a l l e l s i n the laboratory experiments. F i r s t l y , specimens of E. p a c i f i c a migrated less fr e e l y from t h e i r "home" into "foreign" water, than from "home" into "home" water. And secondly, specimens of E. p a c i f i c a sur-vived better i n t h e i r "home" waters than in any "foreign" water. There seems to be l i t t l e doubt that these several pieces of evidence are mutually supporting. Together they appear to point to a s i t u a t i o n wherein neither temperature nor s a l i n i t y play primary roles i n the occurrences of 149 specimens and therefore i n the d i s t r i b u t i o n s of the species, (except i n the conditions of thermocline and h a l o c l i n e i n upper waters), or of populations within the d i s t r i b u t i o n of a single species. In the absence of primary regulatory roles for temperature and s a l i n i t y , other properties must be invoked, as has been discussed above, and at length by Bary (1963a, 1964). What these properties are and how they operate i s not known, but they appear to have t h e i r p a r a l l e l i n such concepts as " b i o l o g i c a l differences"of seawater (Wilson, 1951; Wilson and Armstrong, 1952, 1954) and " q u a l i t i e s " of seawater ( Johnston, 1962, 1964). The present study indicates that the operative pro-perties act d i r e c t l y on the specimens. The inference there-fore i s that these properties are an integral part of the water. On the other hand, the properties of water from one area d i f f e r from those of other, even geographically f a i r l y close, areas. Since, however, there i s a continuity between waters of say, the S t r a i t of Georgia and Indian Arm, i t would seem reasonable-:to assume continuity of these special properties. I f so, then the regulatory processes are exerted not necessarily by d i f f e r e n t properties, but presumably by d i f f e r i n g proportions of properties common to a l l of the waters. There i s the additional p o s s i b i l i t y that i n p a r t i c u l a r situations other, d i s t i n c t properties may be added by, for example, fresh water runoff. Since there i s continuity i n space and i n time i n the properties, demonstrated by the s i m i l a r sorts of reactions 150 i n the f i e l d and laboratory, over a period of two years, the properties must be a r e l a t i v e l y permanent feature, even though c l e a r l y t h e i r "proportions" may be modified, perhaps rapidly, This would suggest they are not solely dependent on being excreted or otherwise obtained as a r e s u l t of seasonal f l u c -tuations of phytoplankton or other a c t i v i t i e s of organisms, (Lucas 1947, 1949; Srinivasagam, 1966) but rather that the influence of these and other organic derivatives on the "unique properties" of a water body may be secondary to the r o l e of inorganic materials. (Johnston, 1964). Of equal importance i s the question of how specimens, and species, react to these properties. I t i s c l e a r that species react to the properties i n d i v i d u a l l y i . e . , t h e i r tolerances d i f f e r — although these may be i n general s i m i l a r among several species, as exemplified by the expatriates i n Indian Arm. I t i s equally c l e a r that among populations of a single species ( E. p a c i f i c a ) associated with d i f f e r e n t bodies of water, tolerances d i f f e r from population to population. In laboratory experiments involving migration, reactions to a "foreign" water were immediate i n that specimens either did not enter the water at a l l or, i f so, then i n fewer numbers than i n "home" water. In the experiments involving survival over extended periods, reactions to "foreign" water varied with the l o c a t i o n from which the water was c o l l e c t e d and i n time with a p a r t i c u l a r water; nevertheless, survival was less than i n the accompanying experiments with "home" water. It i s more d i f f i c u l t to determine how quickly specimens of a 151 species react i n the f i e l d , i n part because stations were separated by one or a few miles and the period between sampling i n one set of conditions and another was a month or longer. Bary (1964) thought that reactions were c h i e f l y at the boundaries between d i f f e r e n t water bodies, and the impression from the f i e l d data i s that t h i s may be the case i n Indian Arm. I f specimens are reacting immediately or slowly to properties, "unique" to bodies of water, they must be able to detect not only the property, favourable or otherwise, but also a gradient i n the concentration of the property. Presum-ably detection of the properties i s physiological and expressed i n behaviour, but how i t i s accomplished i s not known. The aggregation of E. p a c i f i c a away from water i n t r u -ding into Indian Arm would suggest specimens escaped by swimming and t h i s may be a usual reaction where i t i s feas-i b l e . On the other hand, the considerable reduction i n o v e r a l l numbers co l l e c t e d , towards the mouth of the i n l e t i n p a r t i c u l a r , indicate that specimens may have been eliminated by the entering water, or possibly they were flushed out of the i n l e t ; i n either case fewer specimens would be l e f t , except perhaps i n the up-inlet l o c a t i o n . Among the problems the present study opens up i s that exemplified by the d i f f e r i n g reactions of populations of Euphausia p a c i f i c a to t h e i r "home" and to a series of "foreign" waters. The evidence can be interpreted i n two ways. A group of specimens entering B. C.coastal waters may have among themselves a v a r i e t y of tolerances which could 152 enable some specimens to inhabit one set of conditions, and others to inhabit another. This would be feasible i f i n fact the properties to which they were reacting i n d i f f e r e n t waters were common ones and modified only to the extent, for example, that proportions changed i n d i f f e r e n t waters. A l t e r -natively, the specimens entering r;coastal areas could be si m i l a r i n tolerance and subsequently inhabit d i f f e r i n g waters by adapting tojtheir properties possibly i n one genera- . t i o n or more probably over several. Unfortunately, the data from the present study do not indicate which of these a l t e r -natives apply. The usual taxonomic characters used i n the i d e n t i f i -cation of Euphausia p a c i f i c a (eyes large and spherical, lack' of rostrum on carapace, strong denticle near middle of cara-pace, abdomen without denticles or keels and the structure of the male copulatory organ Banner, 1950; Boden, Johnson and Brinton, 1955) were present i n specimens of t h i s species c o l l e c t e d i n Indian Arm, S t r a i t of Georgia and Juan de Fuca S t r a i t . On t h i s basis, they were regarded as l o c a l popula-tions, and not subspecies, of a species. I f i t i s assumed that the populations are p h y s i o l o g i c a l l y adapted (see above) to d i f f e r e n t , but adjoining, habitats perhaps they may be referred to as "ecological races" of a species. In either case, i t i s in t e r e s t i n g to speculate on the properties of the d i f f e r e n t waters, and the reactions of specimens to these, which resulted i n specimens preferring "home" water over "foreign" waters. This i s e s p e c i a l l y so i n view of the 153 continuity of the various waters. From the survey above i t i s apparent that the present study strongly suggests the presence of properties other than (or as well as) temperature and s a l i n i t y acting as a means of regulating occurrences of some pelagic zooplanktonic species. It i s c l e a r also,that many problems have been indicated. There seems l i t t l e doubt, however, that the relationships between species and waters outlined and the physiological problems implied i n these are important to the understanding of the ecology of pelagic organisms. 154 IX. SUMMARY AND CONCLUSIONS Temperature-salinity (T-S) diagrams and the geograph-i c a l d i s t r i b u t i o n s of temperature, s a l i n i t y and density(o"t) have shown the ranges of temperature and s a l i n i t y i n Indian Arm over a two year period including changes associated with seasonal fluctuations and periodic intrusions of- outside water entering the i n l e t from outside, presumably: from the S t r a i t of Georgia through Burrard I n l e t . The adults of four species of euphausiids (Euphausia  p a c i f i c a , Thysanoessa s p i n i f e r a , Thysanoessa longipes and Thysanoessa r a s c h i i ) and the developmental stages of E. p a c i f i c a have been related to|environmental conditions i n Indian Arm by means of Temperature-Salinity-Plankton (T-S-P) diagrams and by p r o f i l e s of the i n l e t showing occurrences i n r e l a t i o n to isotherms, isohalines and isopycnals. Of the four species, E_. p a c i f i c a i s a resident species and i s the most tolerant towards environmental conditions i n Indian Arm, followed by the expatriate species T_. s p i n i f e r a , T_. longipes and T. r a s c h i i i n order of decreasing tolerance. A l l species, whether resident or expatriate, were useful as b i o l o g i c a l indicators of oceanographic changes i n Indian Arm, p a r t i c u -l a r l y with reference to the detection of outside waters entering the i n l e t . Wide variations i n d i s t r i b u t i o n occurred not only amoncpt species but also within the developmental sequence of the resident species, E_. p a c i f i c a ; the e a r l i e r develop-155 mental stages (nauplii, metanauplii) were markedly r e s t r i c t e d i n t h e i r d i s t r i b u t i o n to deeper water when compared with the broad v e r t i c a l d i s t r i b u t i o n of the eggs, l a t e r developmental stages (ca l y p t o p i i , f u r c i l i a ) and the adults. Indications were that temperature and s a l i n i t y may have been, at least i n part, "regulatory factors", p a r t i c u -l a r l y for waters between about 10 m and the surface. The general absence of the expatriate species and the occurren-ces of only small numbers, or more often the absence, of E. p a c i f i c a i n these upper waters may have been dependent on the reactions of specimens towards the maximum tempera-ture and s a l i n i t y changes ( i . e . , thermocline and halocline) c h a r a c t e r i s t i c of the upper waters. That portion of the laboratory study concerned with the migration of euphausiids i n temperature, s a l i n i t y and combined temperature-salinity structures demonstrated relationships s i m i l a r to those for the upper waters i n Indian Arm. In the laboratory the migration of specimens decreased as the temperature increased and s a l i n i t y decreased towards the surface, the e f f e c t becom-ing more pronounced i n tests where the rate of change of temperature and s a l i n i t y were increased and i n tests where temperature and s a l i n i t y structures were combined. These tests indicated, however, that at least some of the specimens were considerably more tolerant of high temperatures and low s a l i n i t i e s than was generally indicated by the f i e l d studies; and t h i s despite the steeper gradients used in the laboratory. From t h i s i t i s suggested that even i n upper waters i n Indian 156 Arm other properties i n addition to temperature and s a l i n i t y , may also have been instrumental i n determining the d i s t r i b u -t i o n of euphausiids. It i s believed that while expatriate species were transported into Indian Arm i n association with intruding waters, the resident species, at least to some extent, was flushed out of the i n l e t along with the subsequent volume displacement and transport of resident water. For expat-r i a t e specimens which have entered the i n l e t and for resident specimens which have remained within the i n l e t , t h e i r occur-rences and d i s t r i b u t i o n i n intermediate-depth and deeper waters indicated the probable presence of regulatory factors other than temperature and s a l i n i t y . This was subsequently demonstrated i n the migration and sur v i v a l of E. p a c i f i c a i n the laboratory. It i s postulated that properties "unique" i n some way to d i f f e r e n t waters, and the reactions of speci-mens towards these, were important. From the f i e l d study i t appeared f i r s t l y , that the expatriates transported by intruding waters into Indian Arm were intolerant of the properties of Indian Arm water, and secondly, that the resident species (at least those which were not flushed out of the i n l e t ) while tolerant of the properties of Indian Arm water reacted adversely towards the properties of intruded waters. Furthermore, general absence of E. p a c i f i c a , T_. s p i n i f e r a and T. longipes from the deep waters, below 120 m, and of T. r a s c h i i from waters below 60m did not appear to be associated with temperature and s a l i n i t y 157 but rather to an adverse reaction of specimens towards the "unique properties" of deep water. In the laboratory specimens of E. p a c i f i c a were, i n general, more tolerant towards "home" water than towards "foreign" waters. Specimens migrated more r e a d i l y and sur-vived i n larger numbers and for longer periods i n "home" waters than i n "foreign" waters or i n mixtures of the two. Again, t h i s was not attri b u t a b l e to temperature or s a l i n i t y but rather to some other property or properties, and the reactions of specimens towards such, i n waters from d i f f e r -ent but (geographically) continuous l o c a t i o n s . The nature of the "unique properties" i s unknown. It i s suggested that the small numbers, and often complete absence of expatriate species i n Indian Arm, during periods when intruded water from outside was decreasing i n influence through mixing and d i l u t i o n with resident water, may be com-parable to the r e l a t i v e l y poor survival i n the laboratory of populations of E. p a c i f i c a c o l l e c t e d from outside ( S t r a i t of Georgia, Juan de Fuca S t r a i t ) of Indian Arm and placed i n Indian Arm water. This would i n f e r , for specimens associated with outside water,a deficiency of some essential property or properties or (and perhaps as well as)the presence of some deleterious property or properties i n Indian Arm water. Si m i l a r l y , the decrease i n abundance and/or s h i f t i n d i s t r i -bution of a resident population of E. p a c i f i c a i n Indian Arm, during periodic intrusions of outside water, may be comparable to the lessened c a p a b i l i t i e s for migration and survival i n the 158 laboratory of J3 . p a c i f i c a c o l l e c t e d i n Indian Arm and placed i n "foreign" waters ( S t r a i t of Georgia, Juan de Fuca S t r a i t and Malaspina S t r a i t ) . This would i n f e r , for a population resident to Indian Arm, a deficiency of essential properties and/or the presence of deleterious properties i n waters from outside of the i n l e t . 159 X. "LITERATURE CITED Banner, A. H. 1950. 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The d i s t r i b u t i o n of Sagitta gazellae Ritter-Zahony. Discovery; Rept., 27: 235-278. 1958. The d i s t r i b u t i o n of the Chaetognatha of the Southern Ocean. Discovery Rept., 29: 199-228. Ekman, S. 1953. Zoogeography of the Sea-.SjJdgwick and Jackson Ltd., London, 417 pp. Fraser, F. C. 1936. On the development and d i s t r i b u t i o n of the young stages of k r i l l (Euphausia superba ). Discovery  Rept., 14: 1-192. Gilmartin, M. 1960. The primary production of a B r i t i s h Columbia f j o r d . Ph. D. Thesis, Univ. B. C. 1962. Annual c y c l i c changes i n the physical oceanog-raphy of a B r i t i s h Columbia f j o r d . J . F i s h . Res. Bd.  Canada, 19(5): 921-974. Haffner, R. E. 1952. Zoogeography of the bathypelagic f i s h , Chauliodus. Systematic Zool., 1(3): 113-133. Hedgpeth, J . W. 1957. Editor, Treatise on marine ecology and paleoecology. 1, Geol. Soc. Amer.Mem.,No.67, New York, 1296 pp. In s t i t u t e of Oceanography, University of B r i t i s h Columbia, Data Report No.18, Indian Arm Cruises, i960. ' 1961. Ibid., Data Report No. 19, B r i t i s h Columbia Inlet Cruises,1961. 1964. Ibid., Data Report No. 24, B r i t i s h Columbia and Alaska Inlet Cruises, 1964. 162 Moore, H. B. 1950. The r e l a t i o n between the scattering layer and Euphausiacea. B i o l . Bull.,99 (2): 181-212 1952. Physical factors a f f e c t i n g the d i s t r i b u t i o n of euphausiids i n North A t l a n t i c . B u l l . Mar. Sc. Gulf and  Caribbean, 1(4): 278-305. Moore, H. B. and E. G. Corwin. 1956. The e f f e c t s of tempera-ture, illumination and pressure on the v e r t i c a l d i s t r i -bution of zooplankton. B u l l . Mar. Sc. Gulf and Caribbean. 6(4): 273-287. Moore, H. B., and M. Foyo. 1963. A study of the temperature factor i n twelve species of oceanic copepods. B u l l . Mar. Sc. Gulf and Caribbean, 13(4): 502-515. Moore, H. B., H. Owre and E. C. Jones. 1953. Planktoniof the F l o r i d a Current. 111. The control of the v e r t i c a l d i s t r i b u t i o n of zooplankton i n the daytime by l i g h t and temperature. B u l l . Mar. Sc. Gulf and Caribbean. 3(2): 83-95. Mullin, M. M. 1963. Some factors a f f e c t i n g the feeding of marine copepods of the genus Calanus. Limnol. and  Oceanogr., 8: 239-250. Paquette, R. G., and H. F. Frolander. 1956. Improvements i n the Clarke-Bumpus plankton sampler. J . Cons. Perm. Internat. Explor. Mer.,22(l): 284-288. Pickford, G. E. 1946. Vampyroteuthis i n f e r n a l i s Chun. An archaic dibranchiate cephalopod. 1. Natural h i s t o r y and d i s t r i b u t i o n . Dana Rept., 29: 1-40. 1952. The Vampyromorpha of the "Discovery" expeditions. Discovery Rept. 26: 197-210. Pickard, G. L. 1955. B r i t i s h Columbia I n l e t s . Trans. Am.  Geophys. Union, 36: 879-901. 1961. Oceanographic features of i n l e t s i n the B r i t i s h Columbia mainland coast. J . F i s h . Res. Bd. Canada, 18: 907-999. Prosser, C. L., and F. A. Brown, J r . 1961. Comparative  Animal Physiology, 2nd ed. W. B. Saunders Co., Philadelphia, 688 pp. Regan, L. 1963. F i e l d t r i a l s with the Clarke-Bumpus plankton sampler. Effects of coarse- and fine-meshed nets over a range of speeds on euphausiid c o l l e c t i o n s . University of  B r i t i s h Columbia, I n s t i t u t e of Oceanography, Manuscript Rept. No. 16. 28 pp., 7 f i g . 163 Salmon, J . T. 1949. New methods i n microscopy for the study of small insects and arthropods. Trans. Roy. Soc. New  Zealand, 77(5): 250-253. Shan, Kuo-cheng. 1962. Systematic and ecological studies on copepoda i n Indian Arm, B r i t i s h Columbia. M. Sc.  Thesis, University of B. C. S h i r a i s h i , K., and L. Provasoli. 1959. Growth factors as supplements to inadequate al g a l foods for Tigriopus  japonicus. Tohoku J . Agr. Res., 10: 8 9 - 9 6 . Srinivasagam, R. T. 1966. E f f e c t of b i o l o g i c a l condition-ing of sea water on development of larvae of a sedentary polychaete. Nature, No. 5063: 1-2. Strickland, J . D. H., and T. R. Parsons. 1961. A manual of sea water analysis. B u l l , F i s h . Res. Bd. Canada, 125: 1-185. Sverdrup, H. U., MU .W. Johnson and R. H. Fleming. 1942. The  oceans, t h e i r physics, chemistry and general biology. Prentice-Hall Inc., New York, 1060 pp. Tabata, S., and G. L. Pickard. 1957. The physical oceanog-raphy of Bute Inlet, B r i t i s h Columbia. J . Fish, Res. Bd. Canada, 14: 487-520. Waldichuk, M. 1957. Physical oceanography of the S t r a i t of Georgia, B r i t i s h Columbia. J . Fis h . Res. Bd. Canada, 14(3): 321-486. Wilson, D. P. 1951. A b i o l o g i c a l difference between natural sea waters. J . Mar. B i o l . Assoc., U.K., 30: 1-26-Wilson, D.P. and F. A. J . Armstrong. 1952. Further experi-ments on b i o l o g i c a l differences between natural sea waters. J . Mar. B i o l . Assoc., U. K. 31: 335-349. 1954. B i o l o g i c a l differences between sea waters; experiments i n 1953. J . Mar. B i o l . Assoc., U.K.33:347-360. 164 TABLE 1. The maximum and minimum temperature, s a l i n i t y and oxygen values recorded i n Indian Arm from January, 1960, through August, 1961. Temperature (C°) S a l i n i t y ( °/oo) Oxygen (ml/1) Maximum Date Station Depth 20.21 Aug. 1,1951 2 0m 27.32 Mar. 23, I960 6 200m 9.53 Feb. 16, 1960 6 0m Minimum Date Station Depth 3.08 Dec.16, 1960 6 0m 2.42 Apr. 20, 1960 2 0m 1.31 Jan. 4, 1960 6 200m T A B L E 2. Euphausia pacifica N O . / m. 3 o 0.1 0.9 O 1.0 - 4.9 O 5.0 - 9.9 O 10.0 - 24.9 O 25.0 - 49.9 O 50.0 - 74.9 Q 75.0 - 86.0 TABLE 3. Thysanoessa spinifera Thysanoessa longipes Thysanoessa raschii N O . / 10 c u . m . o 1.0 " 1.9 O 2 . 0 - 2 . 9 O 3.0 - 5.0 O 5.1 - 9.9 O 10.0 -19.9 O 20.0 "30.3 167 TABLE 4. The maximum and minimum values of temperature and s a l i n i t y i n which the developmental stages of Euphausia p a c i f i c a were c o l l e c t e d i n Indian Arm, from September, 1960 to July-August, 1961. Developmental Stage Temperature (°C) min. max. S a l i n i t y min. (°/oo) max. Adults 5.3 13.8 7.0 27.15 Eggs 7.7 16.8 14.0 27.1 Nauplius I 8.0 11.0 24.7 27.1 Nauplius II 7.85 10.3 25.6 27.18 Metanauplius 7.85 9.4 25.6 27.18 F i r s t Calyptopis 8.0 12.4 23.6 27.18 Second Calyptopis 8.0 12.4 23.4 27.0 Third Calyptopis 7.1 12.5 23.4 26.8 F i r s t F u r c i l i a 8.1 13.2 23.6 27.0 Third F u r c i l i a 8.0 13 .2(18.5) 23.3(22. 0) 27.18 Sixth F u r c i l i a 8.0 13 .8(18.5) 23.3(22. 0) 27.1 168 TABLE 5 The maximum and minimum values of temperature and s a l i n i t y i n which adult specimens of Euphausia p a c i f i c a , Thysanoessa  s p i n i f e r a , Thysanoessa longipes and Thysanoessa r a s c h i i were co l l e c t e d i n Indian Arm, January, 1960 to July-August, 1961. Species Temperature (°C) min. max. S a l i n i t y ( u / o o ) min. max. Euphausia p a c i f i c a 5.3 13.8 7.0 27.3 Thysanoessa s p i n i f e r a 6.6 13.7 14.3 27.3 Thysanoessa longipes 7.6 10.3 24.5 27.15 Thysanoessa r a s c h i i 8.8 11.7 25.7 26.81 '* 169 TABLE 6 The v e r t i c a l migration of Euphausia p a c i f i c a i n r e l a t i o n to s a l i n i t y when varying temperature structures are superimposed upon similar s a l i n i t y structures (Figs. 133, 134 and 135). figure Mean S a l i n i t y Gradient (°/oo/cm Mean Temperature Gradient ) (CO/cm) S a l i n i t y Range of Unrestrictec Migration (100%) S a l i n i t y Range of I Decreasing Migration Limiting S a l i n i t y With no Further Migration 133 134 135 0.38 ( 0.39 0.42 0.08 "Constant" Pemperature) 0.40 0.58 26.5-21.3°/oo 26.9-22.2°/oo 26.9-24*0°/°° 19.7- 8.5°/ot 20.8- 10. 0°/l 22.9- 14.8°/< D 8.5°/oo 10.0°/°c D O 14.8°/oc 170 TABLE 7 The v e r t i c a l migration of Euphausia p a c i f i c a i n r e l a t i o n to temperature, when s a l i n i t y structures are superimposed upon temperature structures (Fig. 136). Mean" Temperature Gradient (C°/cm) Mean S a l i n i t y Gradient (°/oo/cm) Temperature Range of Unrestricted Migration (100%) Temperature Range of Decreasing Migration Limiting Temperature With No Further Migration (a) 0.41 0.00 (constant s a l i n i t y ) 9.0-14.7 °C 16.2-25,5°C 25.5 °C (b) 0.40 0.39 9.0-13.6 °C 14.7-23.0°C 23.0 °C (c) 0.58 0.42 9.0-13.0 °C 14.0-22.3°C 22.3 °C 171 TABLE 8 Survival i n the laboratory of Euphausia p a c i f i c a i n "home" water (Indian Arm) and i n "foreign" waters ( S t r a i t of Georgia, Juan de Fuca S t r a i t and Malaspina S t r a i t ) . Euphausiids c o l l e c t e d i n  Indian Arm. Temperature constant at 10 °C. Waters adjusted to similar s a l i n i t i e s . Figure Date Water 3 a l i h i t y j. / Survival Percentage Days 143a June 16 -Aug. 6, 1965 - I.A. 1 (control') - Geo. 1 - J . de F. 1 26.9,: 26.3 26.5 80% n i l 50% (52) ( 9) (42) 143b Dec.9, 1965-Jan.20,1966 - I.A.(control) - Geo. - J . de F. 26.6 26.8 26.5 100% 50% n i l (43) (43) ( 9) 144a Jan. 26-Mar.14,1966 - I.A.(control) - Geo. - J . de F. 26.9 26.8 26.8 60% 30% n i l (47) (47) (47) 144b Feb.25 -Mar.30,1966 - I.A.(control) - J . de F. - Mai. 26.9 26.5 26.7 60% 10% n i l (33) (33) ( 6) 145a A p r i l 15 -June 1,1966 - I.A.(control) - I.A.-J. de F. (1:1) . - J . de F. J - J . de F. 4 26.9 26.85 26.8 33.1 2 57% n i l 13% n i l (47) (47) (47) (47) 145b A p r i l 15 -June 1,1966 - I.A.(control) - I.A.-Mal.(3:1) - I.A.-Mal.(2:1) - I.A.-Mal.(1:1) - Mai. 26.9 26.88 26.87 26.85 26.8 57% 10% n i l n i l n i l (47) (39) (34) ( 6) ( 3) I.A. - Indian Armj Geo. - S t r a i t of Georgia; J . de F. - Juan de Fuca S t r a i t ; Mai. - Malaspina S t r a i t . u n f i l t e r e d seawater; z undiluted; c i r c l e s ; triangles 172 TABLE 9 Survival i n the laboratory of Euphausia p a c i f i c a i n "home" and "foreign" waters. Euphausiids c o l l e c t e d i n Juan de Fuca S t r a i t . Temperature constant at 10°C. Waters adjusted to sim i l a r s a l i n i t i e s . Figure Date Water S a l i n i t y Survival Percentage Days 146a Dec. 9,1965-Jan.20,1966 - J.de F.(control] - J.de F. - Geo. - I. A. 32.8 1 26.5 26.8 26.6 80% 100% 50% 80% (43) (43) (43) (43) L46b Jan.26 -Feb.25,1966 - J . de F. - Geo. - I. A. 26.8 26.8 26.9 60% 20% 30% (31) (31) (31) J . de F. - Juan de Fuca S t r a i t ; Geo. - S t r a i t of Georgia; I. A. - Indian Arm. undiluted seawater 173 TABLE 10 Survival i n the laboratory of Euphausia p a c i f i c a i n "home" and "foreign" waters. Euphausiids c o l l e c t e d i n the S t r a i t of  Georgia. Temperature constant at 10°C. Waters adjusted to sim i l a r s a l i n i t i e s . Figure Date Water S a l i n i t y Surv Lval Percentage days 147a July 27 -Sept.3,1965 -Geo. 1 -I.A. 1 26.3 26.4 n i l n i l (34) (37) 147b Sept. 8 -Oct.16,1965 -Geo. 1 -I.A. 1 26.8 26.6 50% 40% (37) (37) J . de F. - Juan de Fuca S t r a i t ; Geo.- S t r a i t of Georgia; I. A. - Indian Arm. :;•,'!:. u n f i l t e r e d seawater 174 Fig. 1 — Indian Arm, British Columbia, and adjacent regions. a — Location of oceanographic and plankton stations in Indian Arm. b — Locations of collections of euphausiids and seawater for laboratory studies ( A - Indian Arm, B - Malaspina Strait, C - Strait of Georgia and D - Juan de Fuca Strait ). 175 Fig. 2 — Mean temperature-salinity (T-S) curves for the period from September, 1960 to July-August, 1961, for those standard depths applicable at Stations 2, 6, 9, 12 15 and 23 (see text). Fluctuations in temperature and salinity are shown for surface water (between 0 and about 5m), transition water at intermediate depths (approximately 5 to 75m) and for deep water (between about 75m and the bottom at 200m). .3 — Temperature-salinity diagram of Indian Arm for January, 1960. Inserts show isotherms (a) and isohalines (b) in longitudinal sections of the inlet. g. 4 — As above, for February, 1960. 20 18 a 2 u 10 STATION NUMBERS 6 9 12 IS 23 J A N U A R Y , I960 60 16 120 u e E 180 -— i U 14. PT Oi bj CC Q r) 60' r-RA 12. 120 . 9 . 0 180 IO-50m ' 5 m 75-200m*fe] Om — i — 6 — i — 10 — i — 20 — i — 24 12 14 16 18 SALINITY- ( % o ) 22 26 28 20 STATION NUMBERS 6 9 12 15 FEBRUARY. I960 IO-50i 5 m 0 m 75-200m — i — 12 i i > 14 SALINITY "io" — i — 22 10 18 24 26 28 177 Fig. 5 — Temperature-salinity diagram of Indian Arm for March, 1960. Inserts show isotherms (a) and isohalines (b) in longitudinal sections of the inlet. Fig. 6 — As above, for April, 1960. 20 18 ~ 16 U 14 u rc 3 <I2 ui a I 10 0 60 120 E 180 X r -a 0 Ul Q 60 120 180 STATION NUMBERS 2 6 9 12 15 MARCH . I960 12 IS 23 2 7 . 0 -0 m 5m IO-30m 50 - 200m' - i 1 i —I « I r — l — l — 22 24 26 28 — i — 8 10 12 14 16 18 20 SALINITY \Ao) 20 18 0 i 60 16' 120 o E „ o -= 180 Ul rc < rc ui a ui 10 STATION NUMBERS 6 9 12 15 23 APRIL , I960 •8.0 • X 14. i-a. 0 Ul Q . 60 12' 120 180 5m Om I O - 5 0 m ^ 75-200m* 6 8 10 12 14 16 18 20 22 24 26 28 SALINITY i%o) ' 178 Fig. 7 — Temperature-salinity diagram of Indian Arm for June, 1960. Inserts show isotherms (a) and isohalines (b) in longitudinal sections of the inlet. Fig. 8 — As above, for July, 1960. 20 18 16 U 14 LLI CC => r-< 12 (T U a 10 STATION NUMBERS 6 9 12 15 12 15 23 60 120 180 0 tn i 10 5 -30m J UNE . I960 50m 7S-200m' —r— 20 — i — 22 • 26 12 14 SALINITY 18 24 28 20 18 60 — 16 120 O © •B 180 14 UJ DC <I2 UJ a §io STATION NUMBERS 6 9 12 15 X r-a UJ o 23 13.0 • " o 0 m JULY . I960 5-30m " . o o 50 m 75"200nf i 22 — i r -26 10 12 14 16 18 SALINITY (v&o) 20 24 28 179 Fig. 9 — Temperature-salinity diagram of Indian Arm for September, 1960. Inserts show isotherms (a) and isohalines (b) in longitudinal sections of the inlet. Fig. 10 — As above, for October, 1960. 20 18 L J or r-< or u a 2 LU 10 8-o 60 STATION NUMBERS 6 9 12 is 16 120 . — . E 180 I 14-. r-a 0 UJ Q 60 12- 120 180 S E P T E M B E R . I960 0 m 5 - 50m 75 - 200m 10 12 14 16 18 SALINITY (%o) 20 2 2 2 4 2 6 28 20 18 STATION 6 9 NUMBERS 12 15 23 16 14 ul tr Z3 r-< 12 (X Ul a x V-a ui Q OCTOBER . I960 Om 5 "50m O oo o • 75m 100-200m 10 12 14 SALINITY 18 20 22 24 26 28 180 Fig. 11 — Temperature-salinity diagram of Indian Arm for December, 1960. Inserts show isotherms (a) and isohalines (b) in longitudinal sections of the inlet. Fig. 12 — As above, for January, 1961. 20, STATION NUMBERS 6 9 12 15 DECEMBER . I960 IO-30m % V o 0 <K>. o Y 50-200m * On - i C r -6 8 12 14 16 18 SALINITY \%o) — i — 22 — i — 24 —i i— 26 28 10 20 20, 18 ~ 16^  O 14-1 UJ oc p-< I2J UJ a 2 u) I— I0-I STATION NUMBERS 6 9 12 IS Om J A N U A R Y . I96I 5-50m 7 5 " 2 0 0 m i i i • i • i • 1 ' i ' l 6 8 10 12 14 16 18 . SALINITY ( % o ) - i — 24 i • 26 20 22 28 . 13 — Temperature-salinity diagram of Indian Arm for February, 1961. Inserts show isotherms (a) and isohalines (b) in longitudinal sections of the inlet. g. 14 — As above, for March, 1961. 2 0 18 — 16 U 14 ui rc z> r-< 12 rc U l a 2 10-S T A T I O N N U M B E R S 6 9 12 15 23 F E B R U A R Y . 1961 Om 75-200m —r— 8 10 12 14 S A L I N I T Y ho) 18 2 0 2 2 2 4 2 6 2 8 2 0 18 0 60 _ 16 120 U o e 180 X 14 1-d 0 U l U l rc Q 60 h-< I 2 120 :MPE 180 r^ lO S T A T I O N N U M B E R S 6 9 12 15 23 M A R C H . 1961 Om 0 0 ° I 0 - 50m 5 v '<£' 75-200m I i — 2 6 2 8 —r-6 1 0 12 14 16 18 2 0 S A L I N I T Y (v6o) 2 2 2 4 182 Fig. 15 — Temperature-salinity diagram of Indian Arm for April, 1961. Inserts show isotherms (a) and isohalines (b) in longitudinal sections of the inlet. Fig. 16 — As above, for June, 1961. 201 18 — 16 14. UJ r-< 12^  UJ a UJ t— 10 STATION NUMBERS 2 6 9 1 2 15 2 3 E x u Q 0 m APRIL . 1961 5 " 5 0 m 7 5 - 2 0 0 m — i — 26 10 12 ~I4 16 ' iT SALINITY {%o) — i — 20 22 20, 24 28 STATION NUMBERS o 6 9 12 15 23 O m JUNE . 1961 75-200m'*"' 1 — i — 26 10 12 14 SALINITY I6 0 • 18 20 22 24 28 g. 17 — Temperature-salinity diagram of Indian Arm for July-August, 1961. Inserts show isotherms (a) and isohalines (b) in longitudinal sections of the inlet. g. 18 — Fluctuations in the distribution of density in Indian Arm shown by the three selected isopycnals of c% 19.5, 20.75 and 21.0, between January and June, 1960. STATION NUMBERS 185 Fig. 19 — Fluctuations in the distribution of density in Indian Arm as shown by the three selected isopycnals of fft 19.5, 20.75 and 21.0, between July 1960, and January, 1961. STATION NUMBERS g. 20 — Fluctuations in the distribution of density in Indian Arm as shown by the three selected isopycnals of o"t 19.5, 20.75 and 21.0, betwe February and July - August, 1961. STATION NUMBERS 18JZ Fig. 21 — Temperature-salinity-plankton (T-S-P) diagram of Indian Arm in which the occurrences of adults of Euphausia pacifica are shown in relation to total ranges of temperature (°C) and salinity (o/op) for the period from September, 1960, to July-August, 1961. In this and in Figs. 22-27 specimens are shown only as being present (points within a line or lines) or absent. 18'8 Fig. 22 — Temperature-salinity-plankton (T-S-P) diagram of Indian Arm in which the occurrences of eggs (points within solid lines) and f i r s t nauplius stage (within dotted lines) of Euphausia pacifica are shown in relation to total ranges of temperature (UC) and salinity (°/oo) for the period from September, 1960, to July-August, 1961. Eggs were collected only during.March through July-August, 1961; f i r s t nauplius stage collected only during April through July-August, 1961. 03 _JL_ TEMPERATURE o _ i _ ro _ L _ (•c) _ L _ co _i_ ro o o H coH ro to > r - _ I *~ •H -< ov O m O > z m o 00 > > © z m > O c Ho CO r; c CO H c z m o c i > c G) to m o — - 0 0 ro o " 0 0 0 O ° © roJ ro © o o ro. ro. ro co & g ° o 189 Fig. 23 — Temperature-salinity-plankton (T-S-P) diagram of Indian Arm in which the occurrences of second nauplius stage (points within dotted lines) and metanauplius (within solid lines) of Euphausia pacifica are shown in relation to total ranges of temperature (°C) and salinity (°/oo) for the period from September, 1960, to July-August, 1961. Specimens were collected only during April through July-August, 1961. 20-18 J J U N E , J U L . " A U G . 144 Euphausia pacifica SEPT . , O C T . or or u a § i o . 8-NAUPLIUS TJ METANAUPLIUS MAR., APR. 64 D E C , J A N . , FEB . 8 7—*—r 6 8 ~1 r 10 T T 14 16 18 SALINITY (°/oo) -I 1 r 20 — , r 22 24 I r 26 2 8 19D Fig. 24 — Temperarure-salinity-plankton (T-S-P) diagram of Indian Arm in which the occurrences of f i r s t , second and thrid calyptopis stages (points within solid line) as a group, are shown in relation to total ranges of temperature (°C) and salinity (°/oo) for the period from September, 1960, to July-August, 1961. Calyptopii were collected only during September and October, 1960, and April through July-August, 1961. 20-r 64 J U N E , J U L . " A U G . I4J LU or cc UJ Q. ui H- 10-Q4 Eu phausia pacifica C A L Y P T O P I S i.nr.ui MAR., APR. SEPT., OCT. o o O 0 o 0 0 °0 64 D E C , J A N . , FEB . 8 I 1 1 ' 1 1 1 ~ > — 20 22 24 26 28 8 10 i— 12 T j r-14 S A L I N I T Y i  r 16 18 ( % o ) 1 9 1 Fig. 25 — Temperature-salinity-plankton (T-S-P) diagram of Indian Arm in which the occurrences of f i r s t , third and sixth f u r c i l i a stages (points within solid lines), as a group, are shown in relation to total ranges of temperature (°C) and salinity (°/oo) for the period from September, 1960, to July-August, 1961. F u r c i l i a were collected only during September and October, 1960, and during April through July-August, 1961. 192 Fig. 26 — Temperature-salinity-plankton (T-S-P) diagram of Indian Arm in which the occurrences (points within solid line) of adults of Thysanoessa spinifera are shown in relation to total ranges of temperature (°C) and salinity (°/oo) for the period from September, I960, to July-August, 1961. _ L _ TEMPERATURE CD _i_ C c ) _ l _ O) I oo ro o CD-I OH o m O > z m o CD > o c r-H ,2 Q o CD: Ol Q c z m o c i > c ro-1 CO > 2 > po > -o 30 H -< O H CO m TD H O o O o o ro ro" ro ro of ro . oo 19.3 Fig. 27 — Temperature-salinity-plankton (T-S-P) diagram of Indian Arm in which the occurrences of adult specimens of Thysanoessa longipes (points within solid line) and Thysanoessa raschii (within dotted line) are shown in relation to total ranges of temperature (°C) and salinity ( /oo) for the period from September, 1960, to July-August, 1961. 20-8H I4J U J or 5 I2H cr LkJ a U J H 10 8H 64 J U N E , J U L . " A U G . Thysanoessa longipes ADULTS Thysanoessa raschi ADULTS M A R . , A P R . D E C , J A N . , FEB. 8 S E P T . , O C T . , o o o o o o , f , 6 8 I T 26 —r 10 " T — 12 i 1 r-14 SALINITY 1 r 16 18 (%o ) 20 T r 22 i— 24 28 19.4 Fig. 28 — The geographical occurrences of adults of Euphausia pacifica; (a), Thysanoessa spinifera (b), Thysanoessa longipes (c) and Thysanoessa raschii (d) in longitudinal sections of Indian Arm for the period from September, 1960, through July-August, 1961. Specimens are shown only as being present (hatched areas) or absent. STATION NUMBERS o"i 1 *- 1 i 2 H-CL U ° O i — • ; • L Q •• ' • i i i — i — i 195 Fig. 29 — The geographical occurrences of the developmental stages (eggs (a); f i r s t (b) and second (c) nauplius stages; metanauplius (d); f i r s t , second and third calyptopis stages (e); and f i r s t , third and sixth f u r c i l i a stages (f) ) of Euphausia pacifica in longitudinal sections of Indian Arm for the period from September, 1960, through July-August, 1961. Specimens are shown only as being present (hatched areas)or absent. STATION NUMBERS 196 Fig. 30 — Temperature-salinity-plankton (T^S-P) diagram showing night (blocked-in circles) and day (open circles) occurrences of adults of Euphausia pacifica in relation to temperature and salinity for January, 1960, Insert shows the occurrences in subsurface waters on an expanded scale. Relative abundance (no./m^) is indicated by the diameter of circle (see Table 2). Depths, in metres, indicate vertical ranges of groups of temperature-salinity intercepts and euphausiids at six stations in Indian Arm. Fig. 31 — As above, for February, 1960. 20, 18 — 16^  U I4J, UJ cc UJ a JANUARY. I960 30 m 60m o. •8 90m oo 180 m 7*^7. 26 27 0m 28 i • i • 1 • 1 • i 1 1 i — — r — — , i — 12 14 16 18 20 22 24 26 SALINITY (%o) 6 8 10 28 20, 18 -I6J, O UJ CC Z3 r -< I 2-i CC a 2 UJ 10 FEBRUARY. I960 30m 6 0 m Q 90m 26 27 28 Om • > i • 14 SALINITY 10 12 18 20 22 24 26 28 197 Fig. 32 — Temperature-salinity-plankton (T-S-P) diagram of occurrences of adults of Euphausia pacifica for March, 1960. For details, see caption of Fig. 30. Fig. 33 — As above, for April, 1960. 20, 18 u u CC <\2\ u a £ I0J M A R C H . I960 30m A <£ o 90m 60m O 180m 26 27 28 Om T 10 12 14 16 18 SALINITY Iv&o) 20 22 24 26 28 20-, 18 .— 16 -I4J, L U cr U J a 2 UJ APRIL . I960 30 m oo 60m o n § Q,90m O • ° o° <g> 180m 10 2 6 2 7 28. O m - , , 1 , , • i 1 • i > 1 ' 1 ' 1 • i ' — — i ' r 6 8 10 12 14 16 18 20 22 24 26 28 SALINITY {%o) 19 8 Fig. 34 — Temperature-salinity-plankton (T-S-P) diagram of occurrences of adults of Euphausia pacifica for June, 1960. For details, see caption of Fig. 30. Fig. 35 — As above, for July, 1960. Insert not included. 20, f8 — 164 I'M ui CC ID t-<\2\ rc u a J U N E . I960 726 0 m © 60 m <v om O 180m 27 28 i • 1 • i • 12 14 16 SALINITY (°/6o) 9 30 m 6 8 10 18 ~20 22 ' 24 26 "~ 28 20, "8 — I6JJ u 144 U J rc < I2j U l a £|0J JULY. I960 ~8~ — i — 10 ° • 0 m 30m 60m .p) 90 180m' 12 14 16 18 SALINITY (Ao) 20 — i — 22 — i — 24 — i — 26 28 199 Fig. 36 — Temperature-salinity-plankton (T-S-P) diagram of occurrences of adults of Euphausia pacifica for September, 1960. For details, see caption of Fig. 30. Fig. 37 — As above, for October, 1960. 2 0 18 — 16 U 14 i d CC D 12 10 S E P T E M B E R . I 9 6 0 0 m 30 m 60m * O 90m I IBOnT —I 1 1 1 I r——r—i—r—r— 18 2 0 2 2 2 4 2 6 2 8 ~B~ 10 12 14 16 S A L I N I T Y (%o) 2 0 18 O C T O B E R . I 9 6 0 0m o o • e e o o 30m ft* o o 90m f^S — 16 O 14. UJ CC r> i— < 12 cc UJ a §10. 10 12 14 S A L I N I T Y 18 2 0 22 2 4 2 6 2 8 20 :o Fig. 38 — Temperature-salinity-plankton (T-S-P) diagram of occurrences of adults of Euphausia pacifica for December, 1960. For details, see caption of Fig. 30. Fig. 39 — As above, for January, 1961. 20, 18 — 16^  o K 4 Ul cc D <I24 ui a DECEMBER , I960 0 m T 9.5 8.5 7.5 26 30 m 60 m a O 90 m o Q f 180m 27 28\ I i I r-10 12 14 16 18 20 22 24 26 28 SALINITY (v&o) 20, 18 — «e4 o 14 ui cc 3 12 10 J A N U A R Y . 1961 0 m • 30 m 60 m 9 0g ) 9 0 m 26 27 , 28 i • i » i • i • i • i • i • i i i i i • i 6 8 10 12 14 16 18 20 22 24 26 SALINITY [%o) 28 '201 Fig. 40 — Temperature-salinity-plankton (T-S-P) diagram of occurrences of adults Euphausia pacifica for February, 1961. For details, see caption of Fig. 30. Fig. 41 — As above, for March, 1961. 12 14 16 18 SALINITY l/rjo) 20 2 2 24 26 t 28 MARCH.1961 25 15 m t 60m 3 ° m „ • Q 9 0 m 4» 26 27 28 Om So*, —I— 26 1 ' 81 ' 10 \2~^ 14 16 18 SALINITY (vbo) 20 —i— 22 — r — 24 28 202 Fig. 42 — Temperature-saliniry-plankton (T-S-P) diagram of occurrences of adults of Euphausia pacifica for April, 1961. For details, see caption of Fig. 30. Fig. 43 — As above, for June, 1961. Insert not included. 20, 18 u 14 ui CC 12 10 APRIL . 1961 25 l 5 „ m o 30m 60m 26 0 m 90 m I 80 m 27 28. — i — 26 ~6~ T" — , 1 1 i 1 • i 1 1 — 10 12 14 16 18 SALINITY ( % o ) —I r-20 — i — 22 — i — 24 28 44 — Temperature-salinity-plankton (TsS-P) diagram of occurrences adults of Euphausia pacifica for July-August, 1961. For details, see caption of Fig. 30. 20, 18 — 16^  U 144 Ld rt <I2] u i a PloJ JULY - AUGUST , 1961 0 m 8m ^nsm ~ 30m o e o 45m • 60m 180 m —r-8 — i — 22 — i — 24 — i i — 26 28 10 12 14 16 18 SALINITY \Ao) 20 204 Fig. 45 (a-o) — Longitudinal sections of Indian Arm showing occurrences during the night (blocked-in circles) and day (open circles) of adults of Euphausia pacifica, between January, 1960, and July-August, 1961. Relative abundance (no. /m3) is indicated by the diameter of the c i r c l e . STATION NUMBERS 205 Fig. 46 — Temperature-salinity-plankton (T-S-P) diagram of Indian Arm showing occurrences of eggs of Euphausia pacifica for March, 1961. Depths, in metres, indicate the vertical range from which groups of temperature-salinity intercepts and eggs were obtained at six stations. Insert: the occurrences in longitudinal section of Indian Arm. Relative abundance (no. /m?) is indicated by the diameter of the circle (see Table 2). Fig. 47 — As above, for April, 1961. 2 0 , 18 I d CC z> < 12H CC UJ a i i o j M A R C H . 1961 S T A T I O N 6 . 9 N U M B E R S 12 15 23 0 m l5-60m 8Q#S r90-IOOrrf 2 0 , 10 12 14 S A L I N I T Y 18 2 0 2 2 24 26 2 8 A P R I L . 1961 •18 — 16^ O 14 cc CC UJ a Id I2H 10 E — 60 X eZ 1 2 0 UJ : Q 180 S T A T I O N N U M B E R S 6 9 12 15 o O O o 15" 60m 9 0 - l 8 0 r r l — i • 1 • i ' 1 • 1 • i 1 i i 1 — 10 12 14 16 18 20 2 2 2 4 S A L I N I T Y (%o) 2 6 2 8 206 Fig. 4 8 — Temperature-salinity-plankton (T-S-P) diagram of Indian Arm showing occurrences of eggs of Euphausia pacifica for June, 1961. For details, see caption of Fig. 46. Fig. 49 — As above, for July-August, 1961. 7 g. 50 — Temperature-salinity-plankton (T-S-P) diagram of Indian Arm showing the night (blocked-in circles) and day (open circles) occurrences of the f i r s t nauplius stage of Euphausia pacifica for April, 1961. Depths, in metres, indicate the vertical range from which groups of temperature-salinity intercepts and nauplii were obtained at six stations. Insert: the occurrences i-noa longitudinal section of Indian Arm. Relative abundance (no. /m ) is indicated by the diameter of the circle (see Table 2). 208 Fig. 51 — Temperature-salinity-plankton (T-S-P)' diagram of Indian Arm showing the night (blocked-in circles) and day (open circles) occurrences of the f i r s t nauplius stage of Euphausia pacifica for June, 1961. For details, see caption of Fig. 50. Fig. 52 — As above, for July- August, 1961. I ' l l 1 ' I • I 1 I • I I < 1 I I I t I I t 6 8 10 12 14 16 18 20 22 24 26 28 SALINITY (VOO) 209 Fig. 53 — Temperature-salinity-plankton (T-S-P) diagram of Indian Arm showing the night (blocked-in circles) and day (open circles) occurrences of the second nauplius stage of Euphausia pacifica for April, 1961. Depths, in metres, indicate the vertical range from which groups of temperature-salinity intercepts and nauplii were obtained at six stations. Insert: the occurrences in a longitudinal section of Indian Arm. Relative abundance (no. /m3) is indicated by the diameter of the circl e (see Table 2). Fig. 54 — Temperature-salinity-plankton (T-S-P)^ diagram of Indian Arm showing the night (blocked-in circles) and day (open circles) occurrences of the second nauplius stage of Euphausia pacifica for June, 1961. For details, see caption of Fig. 53. Fig. 55 — As above, for July-August, 1961. 20, 18 — 16^  0 m J U N E . 1961 14 ui rc NUMBERS 12 15 8m * Q o 15 m Vo ' 30 m „° • o 45 m 80M 60m 90m 180m 6 — i — 22 — i — 24 — i — 26 10 12 14 16 18 20 SALINITY \Ao) 28 20 , J U L Y - A U G U S T , 1961 0 m 18 — 16 J u 144 ui rc D cc '2^ Ul a 1104 8 m ° 00 o„ 15 m o o° STATION NUMBERS 6 9 12 IS — 60 £ 1 2 0 Ul O 180 45m 60m 90m 30m 180m —I 1 1 r | i I i— 20 2 2 2 4 2 6 28 ~I0 ' 12 ' 14 16 Ie" SALINITY ( % o ) 211 Fig. 56 — Temperature-salinity-plankton (T-S-P) diagram of Indian Arm showing the night (blocked-in circles) and day (open circles) occurrences of metanauplius of Euphausia pacifica for April, 1961. Depths, in metres, indicate the vertical range from which groups of temperature-salinity intercepts and metanauplii were obtained at six stations. Insert: occurrences in a longitudinal section of Indian Arm. Relative abundance (no. /m3) is indicated by the diameter of the circ l e (see Table 2). 212 Fig. 57 — Temperature-salinity-plankton (T-S-P) diagram of Indian Arm showing the night (blocked-in circles) and day (open circles) occurrences of metanauplius of Euphausia pacifica for June, 1961. For details, see caption of Fig. 56. Fig. 58 — As above, for July-August, 1961. 6 8 10 12 14 16 18 20 22 24 26 28 SALINITY (v6o) 21-3 Fig. 59 — Temperature-salinity-plankton (T-S-P) diagram of Indian Arm showing the night (blocked-in circles) and day (open circles) occurrences of the f i r s t calyptopis stage of Euphausia pacifica for September, 1960. Depths, in metres, indicated the vertical range from which groups of temperature-salinity intercepts and calyptopii were obtained at six stations. Insert: the occurrences in a longitudinal section of Indian Arm. Relative abundance (no":, /m3) is indicated by the diameter of the circle (see Table 2). Fig. 60 — As above, for April, 1961. 20, 18 — 164 u S E P T E M B E R . I960 144 0 m cr ZZ> < 124 cr ui a lio4 STATION 6 9 NUMBERS 12 15 23 30m Q b o 60 m ° 0 o 90 m %9 180m i 22 i 24 20, 10 12 14 SALINITY 18 20 26 28 18 — 164 u A P R I L . 1961 14 cr zz> 12 10 — : 6o i 120 ui a ieo STATION 6 9 NUMBERS 12 15 Om 15-60 m 90-l80nt 1~ —T— 8 "io" i • i • i • i 12 14 16 18 SALINITY [%o) —r— 20 —i— 22 — i • 1— 24 26 28 Fig. 61 — Temperature-salinity-plankton (T-S-P) diagram of Indian Arm showing the night (blocked-in circles) and day (open circles) occurrences of the f i r s t calyptopis stage of Euphausia pacifica for June, 1961. For details, see caption of Fig. 59. Fig. 62 — As above, for July-August, 1961. 215 Fig. 63 — Temperature-salinity-plankton (T-S-P) diagram of Indian Arm showing the night (blocked-in circles) and day (open circles) occurrences of the second calyptopis stage of Euphausia pacifica for September, 1960. Depths, in metres, indicate the vertical range from which groups of temperature-salinity intercepts and calyptopii were obtained at six stations. Insert: the occurrences in a longitudinal section of Indian Arm. Relative abundance (no. /m3) is indicated by the diameter of the circl e (see Table 2). Fig. 64 — As above, for April, 1961. 20, 18 — 164 u 144 ui cc D <I24 ui a § I 0 J S E P T E M B E R . I 9 6 0 S T A T I O N 6 9 N U M B E R S 12 15 0 m 23 30 m C» o 60 m O 90m 8o ISO m' —f 2 8 10 12 14 S A L I N I T Y 2 0 i 2 2 2 4 - 1 — 26 20-, 18 — 164 u 14 rc 3 r-< CC U l a 2 12 10 A P R I L . 1961 E — 60 X t 120 ui Q 180 T S T A T I O N N U M B E R S 6 9 12 15 Om i 12 - 1 ' — 16 (%o) - T r -ie —r— 20 I5"60m 90-IBOnJ ~24 ' 2 6 "~~ 2 8 10 14 S A L I N I T Y 2 2 216 Fig. 65 — Temperature-salinity-plankton (T-S-P) diagram of Indian Arm showing the night (blocked-in circles) and day (open circles) occurrences of the second calyptopis stage of Euphausia pacifica for June, 1961. For details, see caption of Fig. 63. Fig. 66 — As above, for July-August, 1961. 10 12 14 16 18 20 22 24 26 28 SALINITY ( Ao) 217 Fig. 67 — Temperature-salinity-plankton (T-S-P) diagram of Indian Arm showing the night (blocked-in circles) and day (open circles) occurrences of the third calyptopis stage of Euphausia pacifica for October, 1960. Depths, in metres, indicate the vertical range from which groups of temperature-salinity intercepts and calyptopii were obtained at six stations. Insert: the occurrences in a longitudinal section of Indian Arm. Relative abundance (no. /m^ ) is indicated by the diameter of the circle (see Table 2). Fig. 68 — As above, for April, 1961. 2 0 184 u a < I 2 ^ L U a ¥\0\ O C T O B E R , I 9 6 0 0 m S T A T I O N N U M B £ R S 6 9 12 15 23 3 0 m § 8 60m o ° •e o 90m 0° O i80m°8» 2 0 N 1 0 12 14 16 18 S A L I N I T Y \/oo) 2 0 2 2 2 4 2 6 2 8 18 -— 16 H O A P R I L . 1961 N U M B E R S 12 15 I5"60m 90-l80nJ i > 16 (%>) —r— 18 - i — 2 0 - i — 2 2 ~ 2 4 ' 2 6 " ~ 2 8 10 12 14 S A L I N I T Y 218 Fig. 69 — Temperature-salinity-plankton (T-S-P) diagram of Indian Arm showing the night (blocked-in circles) and day (open circles) occurrences of the third calyptopis stage of Euphausia pacifica for June, 1961. For details, see caption of Fig. 67. Fig. 70 — As above, for July-August, 1961. 2 0 , 18 — 164 14. ul C C D r-< 124 cr ui a 1104 J U N E . 1961 0 m 6 STATION NUMBERS 6 9 12 15 —f— 8 —T 12 - r — — r — > — 14 SALINITY 6 m ( ? ) 15m ' i 20 3 0 m 45m £ > 0 6 0 m 9 0 m 1 8 0 m 22 24 26 28 10 18 20, 18' _ 164 u 14 ui cr < I 2 4 ui a 2 £ i o 4 JULY - AUGUST . 1961 T-6 -r-8 STATION 6 9 NUMBERS 12 15 0 m 8 m 1 5 m • O a o • o O 3 0 m 4 5 m 0 ° ° 0 6 0 m ©CP 9 0 m 1 8 0 m — r — 22 • 24 i i 26 28 10 12 14 16 18 SALINITY \Ao) 20 219 Fig. 71 — Temperature-salinity-plankton (T-S-P) diagram of Indian Arm showing the night (blocked-in circles) and day (open circles) occurrences of the f i r s t f u r c i l i a stage of Euphausia pacifica for September, 1960. Depths, in metres, indicate the vertical range from which groups of temperature-salinity intercepts and f u r c i l i a were obtained at six stations. Insert: the occurrencessin a longitudinal section of Indian Arm. Relative abundance (no. /m3) is indicated by the diameter of the circ l e (see Table 2). Fig. 72 — As above, for April, 1961. 6 8 10 12 14 16 18 20 22 24 26 28 SALINITY (>6o) 22D Fig. 73 — Temperature-salinity-plankton (T-S-P) diagram of Indian Arm showing the night (blocked-in circles) and day (open circles) occurrences of the f i r s t f u r c i l i a stage of Euphausia pacifica for June, 1961. For details, see caption of Fig. 71. Fig. 74 — As above, for July-August, 1961. 221 Fig. 75 — Temperature-salinity-plankton (T-S-P) diagram of Indian Arm showing the night (blocked-in circles) and day (open circles) occurrences of the third f u r c i l i a stage of Euphausia pacifica for September, 1960. Depths, in metres, indicate the vertical range from which groups of temperature-salinity intercepts and f u r c i l i a were obtained at six stations? Insert: the occurrences in a longitudinal section of Indian Arm. Relative abundance (no./m3) is indicated by the diameter of the c i r c l e (see Table 2). Fig. 76 — As above, for April, 1961. 20, 18 — I6H] 144 u l cr r-< 124 cr ui a i i o j S E P T E M B E R . I960 0 m STATION 6 9 NUMBERS 12 15 23 ~20~ — i — 22 3 0 m 60m * Q O 90m 8g 180 m* 20 n 10 12 14 SALINITY 18 24 26 28 18 — 164 o 14 cr 12 10 APRIL . 1961 0 e ~ 60 X a 120 STATION NUMBERS 6 9 12 15 180 0 0 m I5"60m 90"I80m — i — 24 i 26 10 12 14 16 18 SALINITY (/'oo) 20 22 28 222 Fig. 77 — Temperature-salinity-plankton (T-S-P) diagram of Indian Arm showing the night (blocked-in circles) and day (open circles) occurrences of the third f u r c i l i a stage of Euphausia pacifica for June, 1961. For details, see caption of Fig. 75. Fig. 78 — As above, for July-August, 1961. 22<3 Fig. 79 — Temperature-salinity-plankton (T-S-P) diagram of Indian Arm showing the night (blocked-in circles) and day (open circles) occurrences of the sixth f u r c i l i a stage of Euphausia pacifica for September, 1960. Depths, in metres, indicate the vertical range from which groups of temperature-salinity intercepts and f u r c i l i a were obtained at six stations. Insert: the occurrences in a longitudinal section of Indian Arm. Relative abundance (no. /m^ ) is indicated by the diameter of the c i r c l e (see Table 2). Fig. 80 — As above, for October, 1960. Fig. 81 — Temperature-salinity-plankton (T-S-P) diagram of Indian Arm showing the night (blocked-in circles)7and day (open circles) occurrences of the sixth f u r c i l i a stage of Euphausia pacifica for June, 1961. For details, see caption of Fig. 79. Fig. 82 — As above, for July-August, 1961 20-18 0 m J UNE . 1961 I 6H NUMBERS 12 IS 8 m <% 15 m °A° 30m V 45m 60 m 180ml 8 10 12 14 16 18 20 SALINITY (/<K>) 22 24 26 28 20! 18 16 JULY - A U G U S T , 1961 0 m 144 a D <I24 u i a u i h - I O J NUMBERS 12 15 Bm 4 « 15 m 30 m 180m —r~ 8 10 12 14 I6.0 . 18 SALINITY l/Oo) 20 22 24 26 28 225 Fig. 83 — Temperature-salinity-plankton (T-S-P) diagram showing night (blocked-in circles) and day (open circles) occurrences of adults of Thysanoessa spinifera in relation to temperature and salinity for January, 1960. Insert shows the occurrences in subsurface waters on an expanded scale. Relative abundance (no. /10m3) is indicated by the diameter of the cir c l e (see Table 3). Depths, in metres, indicate vertical ranges of groups of temperature-salinity intercepts and euphausiids at six stations in Indian Arm. Fig. 84 — As above, for February, 1960. 20, 18 - 1 6 ^ o 14 i d CC 3 12 a 2 Ld 10 JANUARY . I960 7+n; 30m 1 60m 90 m O O 12 180 m 2 6 27 28 0 m i ' i • i 6 8 10 i • i 12 14 16 18 SALINITY (%o) 20 22 24 26 28 20, 18 I d CC <\Z\ CC Ld a 2 Ld 10 FEBRUARY. I960 ~6~ ~8~ • 10 - i — 12 30 m 60 m 90m 180m 26 27 28 0 m i 20 T 24 i 26 14 SALINITY 18 22 28 226 Fig. 85 — Temperature-salinity-plankton (T-S-P) diagram of occurrences of adults of Thysanoessa spinifera for March, 1960. For details, see caption of Fig. 83. Fig. 86 — As above, for April, 1960. 20, 18 -— 16-1 ui cc a. M A R C H . I960 0 m 30mvr" \ • 3 ) 180 m 26 -10 12 14 16 18 20 22 24 26 28 SALINITY 20, 18 — 16^  U 14 Ul cc 12 Q . §io4 APRIL . I960 i 10 0 m 16 30 m o " „ ° 8 26 60 m • • 90m O ° o° og 180 m 27 28 \ 12 14 SALINITY (%o) —r— 18 —r— 20 — i — 22 — i — 24 26 28 227 Fig. 87 — Temperature-salinity-plankton (T-S-P) diagram of occurrences of adults of Thysanoessa spinifera for June, 1960. For details, see caption of Fig. 83. Fig. 88 — As above, for July, 1960. 20 18 — 164 JUNE . I960 0 m I'M u i cc 3 r - . < 124 CC UJ a l i o J 30 m 60m 90-!80m 20, 10 12 14 16 18 20 2 2 24 26 28 SALINITY v4o) 18 — 16^  U 144 u i cc 3 <I24 UJ a 2 10 J U L Y . I960 ° • 0 m e o 6 0 moO 90 iSOm* I » I 10 12 14 16 ! 8 20 22 24 26 28 SALINITY \Ao) 89 — Teraperature-salinity-plankton (T-S-P) diagram of occurrences of dults of Thysanoessa spinifera for September, 1960. For details, see aption of Fig. E3. 90 — As above, for October, 1960. 20, 18 - 1 6 144 ui cc ZD i r ' 2 4 ui Q . 2 10 SEPTEMBER . I960 ~6~ i • i — 8 10 Om 30 m 4 60 m o 90m I80mv i ' i ' i 12 14 16 18 20 22 24 26 SALINITY i%o) 28 20, 18 — 164 144 ul cc ZD r -< 124 CC Ul a i i o j OCTOBER . I960 9.5 8.5 7.5 26 60 m 90 m O ' o 180 m 27 0 m 30m i o °60m 0 9 28 i 12 • i • 14 SALINITY — i — 18 —r— 20 • 22 — i — 26 ~8~ 10 he) 24 28 229 Fig. 91 — Temperature-salinity-plankton (T-S-P) diagram of occurrences of adults of Thysanoessa spinifera for December, 1960. For details, see caption of Fig. 83. Fig.; 92 — As above, for January, 1961. DECEMBER . I960 0 m 9.5 8.5 7.5*»^ 30 m 60 m 90 m OO* 180m 27 28. _• \ I » 1 1 1 r— 22 24 26 28 ~6~ ~8~ 10 12 14 16 18 SALINITY (Ao) 20 JANUARY. 1961 9.5 8.5 • e O 60 m 30 m 0 o • o O/-3K 90m ° 0 | « o 180 m 26 " 27 28. 0 m o o 6 8 10 12 14 16 18 20 22 24 26 28 SALINITY [%o) 93 — Temperature-salinity-plankton (T-S-P) diagram of occurrences dults of Thysanoessa spinifera for February, 1961. For details, see aption of Fig. 83. 94 — As above, for March, 1961. FEBRUARY. 1961 0 m i 10 15m 30 m o o 60m O o 0 0 O o o 9 0 m r o • f • e 0 o O 180m o e 0 0 o 25 26 27 28. \ i < i • 18 — i — 20 12 14 16 SALINITY ° ' o ) 22 24 26 28 M A R C H . 1961 -1-6 8 3 0 m 0 6 . ° m « 0 m • • 8 w „ «S . o isom o 2 5 £ L , 27 0 m 28. \ ft o "io ' \Z ' 14 ' 16 18 20~ SALINITY (>0o) — i > i > i i — 22 24 26 28 231 Fig. 95 — Temperature-salinity-plankton (T-S-P) diagram of occurrences of adults of Thysanoessa spinifera for April, 1961. For details, see caption of Fig. 83. Fig. 96 — As above, for June, 1961. 20, 18 - 1 6 4 O 1*4 Ld CC rj LJ a L J t— 104 APRIL , 1961 0 m 15 "60m 90"l80m 20, —i • 1 • i • 1 ' 1 1 1 i i 1 1 1 1 1 — , 10 12 14 16 18 20 22 24 26 28 SAL IN ITY ( % > ) 18 -164 144 L J cr zz> \-< 12 or L J 0 m J U N E . 1961 8m V , 104 30m 01 15m 2 V . ° 4 5 " 6 0 m o „ „ 90m 5 *& 180m 10 12 14 16 , 4 18 20 22 24 26 28 SALINITY V/6o . 97 — Tempera tu re-sa l i n i t y-p l ank ton '(T-S-P) diagram of occurrences adu l t s of Thysanoessa s p i n i f e r a f o r Ju l y-August , 1961. Fo r d e t a i l s , see c ap t i on of F i g . 83. 20, o o J U L Y - A U G U S T 1961 0 m 0 18 0 U e o 14 UJ CC t-< 12 CC  y c u a 2 0 • Bm A :9 30 m ° o a ti1 r- 10 60 mOcr 8- 9 0 m M ^ 1 60 m 6 1 1 i 1 1 1 - I 1 I I I I I • I • I ' 1 ' 1 ' 1 ' I ' 1 ' t 6 8 10 12 14 16 18 20 22 24 26 28 SAL IN ITY (%o) 233 Fig. 98 £a-o) — Longitudinal sections of Indian Arm showing occurrences during the night (blocked-in circles) and day (open circles) of adults of Thysanoessa spinifera, between January, 1960, and July-August, 1961. Relative abundance (no. /lOm^) is indicated by the diameter of the c i r c l e . STATION NUMBERS 234 Fig 99 — Temperature-salinity-plankton (T-S-P) diagram showing night (blocked-in circles) and day (open circles) occurrences of adults of Thysanoessa longipes in relation to temperature and salinity for January, 1960. Relative abundance (no. /10m3) is indicated by the diameter of the circ l e (see Table 3). Depths, in metres, indicate the vertical range of groups of temperature-salinity intercepts and euphausiids at six stations in Indian Arm. Fig. 100 — As abpve, for February, 1960. 20-1 18 — 16-O 14^ DC Z) t-CC LU a FEBRUARY . I960 0 m 30 m 60-|80m I • I ' r — i 1 1 r — i 1 i 1 1 1 1 1 • i • i 1 — 6 8 10 12 14 I 6 . 0 , . 18 2 0 2 2 24 2 6 28 SALINITY l/<5o) 101 — Temperature-salinity-plankton (T-S-P) diagram of occurrences f adults of Thysanoessa longipes for March, 1960. For details, see aption of Fig. 99. 102 — As above, for April, 1960. 20 M A R C H . I960 184 — 16-O 144 ui cc ZZ> <I2J ui a 2 ui H 104 0 m 3 0 " 6 0 m $ 90-J80m <gp i ' i • i » i • i • i • i • • - • • i • • • 6 8 10 12 14 I6_ 18 20 22 24 26 28 SALINITY {%o) 2 0 n APRIL . I960 184 i.e-j u o 14, ui cc ZD U l CL 2 Ul h— I O H 0 m 30m 60-180 m "5 ' 10 ' J2 ' U ' 16 ' 18 " 20 " 22 ' 24 ' 26 "~ 28 SALINITY (%o) . 103 — Temperature-salinity-planktori (T-S-P) diagram of occurrences of adults of Thysanoessa longipes for June, 1960. For details, see caption of Fig. 99. g. 104 — As above, for July, 1960. 20 181 16 JUNE . I960 14-LU r - . <I2^ LU a 2 u . f-IOJ 0 m 30 m O a o 60m , 90 " 180m T — i — > — » — • — i — • i — i — • — i i • i • i i i 10 12 14 I 6. 0 . . 18 2 0 2 2 24 26 SALINITY [Aol 28 20 n 18 — 16^  144 LU or LU a 2 cu , r - 104 J U L Y . I960 0 m 30m o O 60m o o° • 90-l80m 10 12 14 16 18 SALINITY iAo) 20 22 24 26 28 237 Fig. 105 Temperature-salinity-plankton (T^S-P) diagram of occurrences of adults of Thysanoessa longipes for September, 1960. Insert shows the region which is presented on an expanded scale in subsequent months. For details, see caption of Fig. 99. Fig. 106 — As above, for October, 1960. Insert shows the occurrences in subsurface waters on an expanded scale of temperature and salinity. T 10 12 ' 14 ' 16 ' is SALINITY ( % 0 ) 20 22 24 26 28 20 18 — 16 O 14, ui cr z> t-< 12 cr a 2 ui 1 a O C T O B E R . I960 9.5 ~6~ 0 m 30m o""" 0 ° o60m o a 10 12 • 1 1 14 SALINITY "l8~ • 20 1 22 24 26 28 238 Fig. 107 — Temperature-salinity-plankton (T-S-P) diagram of occurrences of adults of Thysanoessa longipes for December, 1960. For details, see caption of Figs. 99 and 106. Fig. 108 — As above, for January-, 1961. 20, 18 — 164 u K 4 UJ or 3 <!2 j U J a §104 D E C E M B E R , I960 9.5 8.5 30m _ o 60m • D • 90m 0 o o o o o ® 0 , O 180 m 26 27 28 A 0m — i 1 — — i 1 1 • 1 1- 1 i -i— 8 10 12 14 16 18 SALINITY iAo) 20 — i — 22 — i — 24 26 28 20, 18 — 164 u 14 U J or 3 12 10 J A N U A R Y . 1961 0 m 9.5 8.5 7.5 30 m 60 m , ° 90m o 180m 26 27 28. — i • i • i • — r ' 1 • I ' 1 ' r — — T — i — 10 12 14 16 18 20 22 24 26 SALINITY {%o) 28 239 Fig. 109 — Temperature-salinity-plankton (T-S-P) diagram of occurrences of adults of Thysanoessa longipes for April, 1961. For details, see captions of Figs. 99 and 106. Fig. 110 — As above, for June, 1961. 20, 18 - 1 6 4 u 144 u i cc 3 cl '24 u i a 2 u i 10 APR I L . 1961 8.54 7.5-Urr 15m 30m ° ° O 60m 90m 180m 25 , 26 27 28 Om I i I i I 20, 10 12 14 16 18 20 22 24 2 6 28 SALINITY i%o) 18 -164 U 144 u i cc . 3 \— < 124 cc u i a JUNE.1961 9.5 8.5 7.5 25 v o o o Q 60m O ° 75m 90m " ©• •* w 0 0 180m 8» 8 m 15m \. O 30m X o ° •e, , ' 26 27 28 i 12 • i • 14 SALINITY 8 10 18 20 22 24 • 26 28 . I l l — Temperature-salinity-plankton (T-S-P) diagram of occurrences of adults of Thysanoessa longipes for July-August, 1961. For details, see captions of Fig. 99 and 106. 20 "8 JULY - A U G U S T . 1961 0 m - 1 6 4 u 144 ui or <I24 ui a. § I 0 J 9.5 8.5 7.5 25 ~6~ O 60m 75m o o o o 90m 180 m 26 27 ,° 8 m 00 o 0 15 m O oO o ° ° ° 30 m • o o **••. , ° ° " 4 5 m 28 • ' < ' I < 1 i 1 — 10 12 14 16 18 SALINITY \Ao) 20 i 22 24 i i 26 28 241 Fig. 112 (a-o) — Longitudinal sections of Indian Arm showing occurrences during the night (blocked-in circles) and day (open circles) of adults of Thysanoessa longipes, between January, 1960, and July-August, 1961. Relative abundance (no. /I0m^) is indicated by the diameter of the c i r c l e . STATION NUMBERS 242 Fig. 113 — Temperature-salinity-plankton (T-S-P) diagram showing night (blocked-in circles) and day (open circles) occurrences of adults of Thysanoessa raschii inrrelation to temperature and salinity for July, 196 0. Depths, in metres, indicate the vertical range of groups of temperature-salinity intercepts and specimens at six stations. Insert shows the occurrence in a longitudinal section of Indian Arm. Relative abundance (no. /10m3) is indicated by the diameter of the circle (see Table 3). Fig. 114 — As above, for September, 1960. 243 Fig. 115 — Temperature-salinity-plankton (T-S-P) diagram of occurrences of adults of Thysanoessa raschii for October, 1960. For details, see caption of Fig. 113. Fig. 116 — As above, for December, 1960. 20 OCTOBER . I960 18-— 161 O 14. or <I2J LU a 2 LU i- 104 0 m STATION 6 g NUMBERS 12 15 3 0 m — i — 22 — i — 24 <><*> ° A 0 ° 6 0 m O 9 0 m 160 m % 10 12 14 SALINITY 16^ 18 20 201 26 28 DECEMBER . I960 18. 16-144 LU or i-< 124 or LU a 2 LU H I0J 0 e — 60 I -LU' Q leo STATION 6 9 NUMBERS I2 15 23 0 m 3 0 m 9 0 m °% 1 8 0 m V 10 12 14 SALINITY 16. 18 20 22 24 26 28 . 117 — Temperature-salinity-plankton (T-S-P) diagram of occurrences of adults of Thysanoessa "rasch"ii for July-August, 1961. For details, caption of Fig. 113. 245 Fig. 118 — Temperature and salinity structures in Indian Arm with respect to the vertical distribution and abundance of Euphausia pacifica at Station 9, night and day collections combined, February, 1961. TEMPERATURE ( °C ) SALINITY (%0) 246 Fig. 119 — Temperature and salinity structures in Indian Arm with respect to the vertical distribution and abundance of Euphausia pacifica at Station 9, night and day collections combined, March, 1961] 247 Fig. 120 — Temperature and salinity structures in Indian Arm with respect to the vertical distribution and abundance of Euphausia pacifica at Station 9, night and day collections combined, June, 1961. TEMPERATURE C O 5 10 15 20 25 30 SALINITY (% 0) g. 121 — Photograph of apparatus used in observing the migration of euphausiids in temperature and salinity structures in the laboratory. Front view. g. 122 — Photograph of apparatus used in observing the migration of euphausiids in temperature and salinity structures in the laboratory. Back view. Fig. 123 — Photographs of apparatus used in observing the migration of euphausiids in the laboratory. Layers of differing s a l i n i t i e s are alternately stained in order to demonstrate the establishment and nature of the salinity structure (salinity variation of 1.3 °/oo between layers or a mean gradient of 0.4 °/oo/cm over the entire column). Fig. 124 — Vertical migration in the laboratory (numbers reaching a particular level as percentage of total migrations) of Euphausia pacifica from Indian Arm, in sal i n i t y structures composed of "home" water (Indian Arm) and of "foreign" waters (Strait of Georgia, Juan de Fuca Strait ) . Mean salinity gradient of 0.4 °/oo/cm; temperature constant. : mean percentage migration for five tests in salinity structures c^omposed of Indian Arm water. Twenty adults in each test. Individual tests on April 1 ( • ), April 2 ( • ) , April 30 ( • ), June 26 ( A ) and July 9 ( X ), 1964. : mean percentage migration for three tests in salinity structures composed of "foreign" waters. Twenty adults in each test. Individual tests on May 23 ( D ) and June 12 ( O ), 1964, in Juan de Fuca Strait water, and on September 29 ( A ), 1964, in Strait of Georgia water. lOCh 8 0 H < cc o 604 INDIAN A R M / • / / 4 / ix x A .Q>oA—• J U A N DE F U C A , G E O R G I A 40H 20H OH / V / A A' * A / b b • A(3 0 5 T 0 n — 15 2 0 —i 1 25 27 S A L I N I T Y (%o) 252 Fig. 125 — Vertical migration in the laboratory of Euphausia pacifica, adults and f u r c i l i a , from Indian Arm in a salinity structure composed of Indian Arm water. Mean salinity gradient of 0.4 °/oo/cm; temperature constant. Twenty adults and 20 f u r c i l i a in the test. June, 26, 1964. SALINITY ( % o ) 253 Fig. 126 — Vertical migration in the laboratory of Euphausia pacifica from Indian Arm in relation to rate of change in salinity structures. Twenty adults in each of two tests in salinity structures with salinity decreasing in "steps" approximating 1.3 °/oo (A) and 3.0 °/oo (B) per layer. Temperature constant. July 9, 1964. SALINITY (%o) 0 5 10 15 20 25 28 0 - j - J 1 — « ' 1 1 60 254 Fig. 127 — A composite diagram showing maximum and minimum sa l i n i t i e s in relation to the vertical migration of adult Euphausia pacifica in the laboratory, o - mean percentage migration for five tests, April - July, ' 1964, in a mean salinity gradient of 0.4 °/oo/cm; • - percentage migration for one test, May 23, 1964, in a mean salinity gradient of 0.3 /oo/cm. Twenty specimens in each test. Temperature constant. % MIGRATION 255 Fig. 128 — Comparison of the vertical migration in the laboratory of Euphausia pacifica and Thysanoessa spinifera from Indian Arm in a salinity structure composed of Indian Arm water. Twenty adults of each species in each of two tests, in a structure with salinity decreasing at approximately 3.0 °/oo per layer. Temperature constant. July 9, 1964. 0 0 I OH 20-\ e I 30 ' r-CL Ld Q 40H 5 0 4 SALINITY (% 0) 10 _ L _ 15 i 20 i 25 • 28 0 — 9 4 - r l ^ ^ - 2 0 l00"{^ )'67 100. 100 O-Euph ausia pacifica W\-Thysanoessa spinifera 100— 100 60 256 Fig. 129 — Vertical migration in the laboratory of Thysanoessa longipes from the Strait of Georgia in a salinity structure composed of Strait of Georgia water. Fifteen adult euphausiids in a mean salinity gradient of 0.4 /oo/cm. Temperature constant. September 30, 1964. SALINITY ( %o) 5 10 15 20 25 30 257 Fig. 130 — V e r t i c a l migration in the laboratory (numbers reaching a particular' level as percentage of total migrations) of Euphausia pacifica from Indian Arm in temperature structures composed of Indian.Arm water. Salinity constant. Individual tests on October 22 ( A , o ), 1965, and on March 3 (• ), 1966. Twenty adults in each test. 60 258 Fig. 131 — A summary diagram showing temperature structures in the laboratory in relation to the migration of Euphausia pacifica from Indian Arm. Salinity constant. Migration tests on October 15 - 22, 1965 and on March 3, 1966. Twenty adults in each test. TEMPERATURE C O 259 Fig. 132 - - V e r t i c a l migration in the laboratory of Thysanoessa spinifera from Indian Arm in a temperature structure composed of Indian"^rUT^ite"r l^ffi c o n s t a n t - T w e n t y adults in a temperature structure of 0.68 uC/cm. March 3, 1966. 260 Fig. 133 — Vertical migration in the laboratory of Euphausia pacifica from Indian Arm in combined temperature and salinity structures composed of Indian Arm water. Mean percentage migration of five tests, April -July, 1964. Twenty adults in each test. a o X I— Q. LJJ Q 0-10-20-30-40-50-60 TEMPERATURE C O 5 20 30 i ME GRAC TC7 c m AN MENT S%o/cm 0.08 0.38 o—o % MIGRATION i 5 . 1 0 15 SALINITY (%o) 20 25 28 261 Fig. 134 — Vertical migration in the laboratory of Euphausia pacifica from Indian Arm in combined temperature and salinity structures composed of Indian Arm water. Twenty adults in the test. October 12, 1965. TEMPERATURE C O 10 15 2 0 _ j 25 i 28 ME GRAD T C % m AN IENT S%o/cm 0.40 0.39 A o—o V V 023-I oo1 % MIGRATION 0 i 5 — i 1 10 15 S A L I N I T Y (%o) 20 25 28 262 Fig. 135 — Vertical migration in the laboratory of Euphausia pacifica from Indian Arm in combined temperature and salinity structures composed of Indian Arm water. Twenty adults in the test. March 4, 1966. 0 5 _ L _ TEMPERATURE (°C) 10 15 2 0 i 25 i 28 10-20-£ o a Ld Q 30" 40 50-ME GRAD TC7 c m AN IENT S%o/cm 0.58 0.42 1 % MIGRATION 1 60 0 i 5 10 15 SALINITY (%o) 20 25 28 263 Fig. 136 — A summary diagram showing the effect on the vertical migration of Euphausia pacifica, with respect to temperature, when salinity structures are imposed-'upon temperature structures. Solid line represents the mean percentage migration for three tests, October 15 - 22, 1965. Dashed line represents a migration test on October 12, 1965. Dotted line represents a migration test on March 4, 1966. Twenty adults in each test. TEMPERATURE C O 264 F i g . 137 — A summary diagram comparing the d i s t r i b u t i o n and m ig ra t i on of Euphausia p a c i f i c a w i t h r e spec t to temperature and s a l i n i t y , i n I nd ian Arm and i n the l a b o r a t o r y . Labora to ry r e s u l t s are presented as contours a t 0, 25 , 50, 75, 100% m ig ra t i ons i n c o n d i t i o n s of : O - s a l i n i t y s t r u c t u r e s w i th constant temperature (mean of f i v e t e s t s , A p r i l - J u l y , 1964) • - temperature s t r u c t u r e s w i t h constant s a l i n i t y (mean of three t e s t s , October 15 - 22, 1965) - combined temperature and s a l i n i t y s t r u c t u r e s ; A - one t e s t , October 12 , 1965 and • - one t e s t , March 4, 1966. Presence i n the f i e l d ( Ind ian Arm) r e l a t i v e to temperature and s a l i n i t y : \\\\\\ between December and March, 1960 - 1 9 6 1 ; / / / / / / / between A p r i l and October , 1961.) TEMPERATURE ( ° C ) 265 Fig. 138 — Summary diagrams comparing the general occurrences and the migrations of Euphausia pacifica, with respect to temperature and salinity in Indian Arm and in the laboratory. top Distributional limits of E. pacifica in Indian Arm for one year (1960 - 1961). Zone 1 - maximum abundance of specimens Zone 2 - specimens few or rare Zone 3 - specimens not collected bottom Migration of E. pacifica in the laboratory. Zone A - unrestricted migration Zone B - decreasing migration Zone G - no migration SALINITY Woo) 266 Fig. 139 — Vertical migration in the laboratory of Euphausia pacifica in "home" water (Indian Arm) and in "foreign" water (Juan de Fuca Strait), when neither temperature nor salinity are limiting. Salinities are indicated; temperature, 10°C. Migrations in three variations of light intensity indicated by | ; 15 adults in each test. June 18, 1965. a. Migration in a column of Indian Arm water with no salinity decrease (control). b. Migration in a column of Indian Arm water with a small salinity decrease (1.32 °/oo) separating lower and upper waters. c. Migration in a column containing two waters (Indian Arm and Juan de Fuca Strait) separated by a small salinity decrease (1.07 °/oo). i (H 20H X CL Ul Q 40-50H 60 1fffi?T WATT , N D , R E C T — i uib d > — INDIAN ARM 26.760/00 O O O O 8 o (CONTROL) INDIAN ARM 26.76 0/00 a 267 Fig. 140 — Vertical migration in the laboratory of Euphausia pacifica in "home" water (Juan de Fuca Strait) and in "foreign" water (Indian Arm), when neither temperature nor salinity are limiting. Salinities are indicated; temperature, 10°C. Migrations in three variations of light intensity indicated by'. ^  ; 15 adults in each test. December 10, 1965. a. Migration in a column of Juan de Fuca Strait water with no salinity decrease (control). b. Migration in a column of Juan de Fuca Strait water with a small salinity decrease (0.94 °/oo) separating lower and upper waters. c. Migration in a column containing two waters (Juan de Fuca Strait and Indian Arm) separated by a small salinity decrease (0.26 °'/oo). 10-20-e o I I— 30 a . UJ o 40-50 60 100 6 WATT WATT A INDIRECT JUAN DE F U C A 0 26.O6 0/OO 0 0 8 8 o o § § 8 (CONTROL) JUAN DE FUCA 26.06*/oo a 268 Fig. 141 — Survival in the laboratory of Euphausia pacifica from Indian Arm in dilutions of Indian Arm water. Ten adults transferred to progressively diluted waters at two day intervals until none survived; 10 adults in control at 26.9 °/oo during the ten-fdays of March 12 - 21, 1966. D A Y S 9 g. 142 — Survival in the laboratory of Euphausia pacifica from Indian Arm in dilutions of Indian Arm water. Seventeen adults transferred to progressively diluted waters at two-day intervals until nonesurvived; 17 adults in control at 26.9 °/oo during the twelve days of April 18 -1966. 270 Fig. 143 — Survival in the laboratory of Euphausia pacifica in "home" water (Indian Arm) and in "foreign" waters (Strait of Georgia, Juan de Fuca St r a i t ) . Indian Arm specimens in "home" water acts as a control. a. — 10 adults/4 l i t r e s in each of the three waters. Salinity range, 26.3 - 26.9 °/oo; temperature, 10°C. June 16 - August 6, 1965. b. — 10 adults/4 l i t r e s in each of the three waters. Salinity range, 26.5 - 26.8 °/oo; temperature, 10°C. December 9, 1965 - January 20, 1966. 100 • o-o—o—o—o o ov-INDIAN ARM \ ( CONTROL) k-JUAN DE FUCA 100 80 4 0 2 0 30 40 NUMBER OF DAYS IV INDIAN ARM (CONTROL) o \ > — o - o |! 60 > cc D 40 20H o-o- GEORGIA o o—o -JUAN DE FUCA T T T 10 20 30 40 NUMBER OF DAYS 50 271 Fig. 144 — Survival in the laboratory of Euphausia pacifica in "home" (Indian Arm) and in "foreign" waters (Strait of Georiga, Juan de Fuca Strait and Malaspina Strait). Specimens in Indian Arm water act as a control. a — 10 adults/ 4 l i t r e s of each of the three waters. Salinity range, 26.8 - 26.9 °/oo; temperature, 10°C. January 26 - March 14, 1966. b — 20 adults/ 4 l i t r e s in Indian Arm (control) and Juan de Fuca Strait waters; 10 adults/ 4 l i t r e s of Malaspina Strait water. Salinity range, 26.5 - 26.9 9 / 0 0 ; temperature, 10°C. February 25 - March 30, 1966. -INDIAN ARM (CONTROL) -JUAN DE FUCA o—o-cv 10 20 30 40 NUMBER OF DAYS 50 100 804 i o—o-o—o—o O — O — < 60 > cr D * INDIAN ARM (CONTROL) o o—o 40 4 2 0 H - GEORGIA (MALASPINA) -JUAN DE F U C A 0 10 20 30 40 1 50 NUMBER OF DAYS 145 Survival in the laboratory of Euphausia pacifica in "home" water (Indian Arm), in "foreign" water (Juan de Fuca Strait) and in a mixturesof equal parts of the two. Specimens in Indian Arm water act as a control. Ten adults/ 4 l i t r e s (total of 40 animals) in each (circles) of Indian Arm, diluted Juan de Fuca Strait and mixture waters, with a salinity range of 26.8 - 26.9 °/oo. Ten adults/4 l i t r e s in undiluted (33.1 °/oo - triangles) water from Juan de Fuca Strait. Temperature, 10°C. April 15 - June 1, 1966. Survival in the laboratory of Euphausia pacifica in "home" water (Indian Arm), in "foreign" water (Malaspina Strait) and in three mixtures of these. Ten adults/ 4 l i t r e s (total 40 animals) in Indian Arm water (control); 10 adults/ 4 l i t r e s in Malaspina water and in each of the mixtures. Salinity, 26.8 - 26.9 °/oo; temperature, 10°G. April 15 -June 1, 1966. 100 -it 80-< 60H > or oo 40->5 20-\ VNx5oo-0—0—< 0 0 \— INDIAN ARM °- (CONTROL) •HNDIAN ARM N °\£jUAN DE F C J ^ ? \ > T T 10 20 30 40 NUMBER OF DAYS 50 100 INDIAN ARM O. (CONTROL) \ - 2 5 % MALASPINA \-33% \M ALA-V SPINA \ 1-50% " \ \ M ALA SPIN A %^"^  MALASPINA "O-O-O—o *o-o 1 — 10 — 1 — 20 o-o-o 30 40 50 NUMBER OF DAYS 273 Fig. 146 — Survival in the laboratory of Euphausia pacifica in "home" water (Juan de Fuca Strait) and in "foreign" waters (Strait of Georgia, Indian Arm). Specimens in Juan de Fuca water (diluted and undiluted) act as controls. Temperature, 10°C. a — 10 adults/ 4 l i t r e s in each of diluted Juan de Fuca Strait, Strait of Georgia and Indian Arm waters, with a salinity range of 26.5 - 26.8 °/oo; 10 adults/ 4 l i t r e s in undiluted (32.8 °/oo) water from Juan de Fuca Strait. December 9, 1965 - January 20, 1966. b — 10 adults/ 4 l i t r e s in each of diluted Juan de Fuca Strait, Strait of Georgia and Indian Arm waters, with a salinity range of 26.8 - 26.9 °/oo. January 26 - February 25, 1966. 100 1 80-< 6 0 H > > cr 40H o-o—o-o—o-JUAN DE FUCA o o o—I—o—o (DILUTED CONTROL) \, JUAN DE FUCA (CONTROL) - o — o — " 8 " INDIAN ARM -o—o- \ -o-o GEORGIA 20-0 I 1 1 1 — 0 20 30 40 NUMBER OF D A Y S — I 50 -JUAN DE FUCA (DILUTED CONTROL) NUMBER OF D A Y S 274 Fig. 147 — Survival in the laboratory of Euphausia pacifica in "home" water (Strait of Georgia) and in "foreign" water (Indian Arm). Specimens in Strait of Georiga water act as a control. a — 10 adults / 4 l i t r e s In the two waters. Salinity range, 26-.-3 - 26.4 °/oo; temperature, 10°C. July 27 - September 3, 1965. b — 10 adults / 4 l i t r e s in the two waters. Salinity range, 26.6 - 26.8 °/oo; temperature, 10°C. September 8 - October 16, 1965. 1001 80-g 60H > cc c/) 40-20 0 a o — - o — —o \-INDIAN ARM "GEORGIA1* V(DI LUTED \ £0NTgQy\ 0 10 20 NUMBER OF DAYS 50 100 o b-o 20-0 VINDIAN ARM BM.Oa»OsBOataO— O GEORGIA (DILUTED CONTROL) 0 10 20 30 40 50 NUMBER OF DAYS 

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