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Growth and morphometry of the pygmy whitefish (Prosopium coulteri) in British Columbia McCart, Peter James 1963

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GROWTH AND MORPHOMETRY OF THE PYGMY WHITEFISH (PROSOPIUM COULTERI) INBRITISH COLUMBIA by PETER JAMES MCCART B.A. The U n i v e r s i t y of Oregon, 1958 A Thesis Submitted i n P a r t i a l F u l f i l m e n t of the Requirements f o r the Degree of MASTER OF SCIENCE i n the DEPARTMENT OF ZOOLOGY We accept t h i s t h e s i s as conforming t o the r e q u i r e d standard THE UNIVERSITY OF BRITISH COLUMBIA October, 1963 I n 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 m a y b e g r a n t e d b y t h e H e a d o f m y 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 m y w r i t t e n p e r m i s s i o n . I n s t i t u t e o f F i s h e r i e s D e p a r t m e n t o f Z o o l o g y 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 V a n c o u v e r 8, C a n a d a 6 S e p t e m b e r 1963 i ABSTRACT The present study i s , i n par t , a descr ip t ion of mer i s t i c v a r i a t i o n i n the pygmy whi t e f i sh , Prosopium c o u l t e r i , of B r i t i s h Columbia f i s h wi th those of other areas. The species was shown to be h igh ly var iab le m e r i s t i c a l l y both wi th in and between populations. There are ind ica t ions i n some characters of a north-south c l i n e of mer i s t i c counts. One character ( g i l l raker counts) seems to form a V-shaped curve of v a r i a t i o n . The major part of the study i s a comparison of the growth and r e l a t i v e growth of f i s h from four B r i t i s h Columbia lakes . The two "giant" forms from MacLure and McLeese Lakes are more l i k e one another i n r e l a t i v e growth than l i k e e i ther of the two dwarf forms inhab i t ing Cluculz Lake or Tacheeda Lake. The possible r e l a t ionsh ip between growth, form and environment i s discussed. v i i i ACKNOWLEDGEMENTS The author wishes to thank Dr. C. C. Lindsey who suggested the problem and who guided the ear ly f i e l d work, and Dr. R. Rosenblatt and Dr. P. A . Lark in who provided invaluable advice concerning the analys is and in te rpre ta t ion of data. Thanks are a l so due to Dr. N . J . Wilimovsky, Dr. T. G. Northoote, and Dr. P. A . Dehnel for c r i t i c a l l y reading the manuscript, and to Dr. J . D. McPhail for much useful advice as w e l l as to Mr. J . Nelson, Mr. D. Gordon and Mr. R. Rounds for t h e i r assistance i n f i e l d work. The author i s indebted to the F isher ies Research Board of Canada and the Nat ional Research Council for a Fisher ies Research Board of Canada Studentship awarded for 1962 - 1963. i i TABLE OF CONTENTS page INTRODUCTION 1 MATERIALS AND METHODS 3 F i e l d data 3 Counts and Measurements 4 Age and growth 8 Food s t u d i e s 9 The h a b i t a t 9 RESULTS M e r i s t i c s I-7 Age and growth 33 Age at m a t u r i t y 61 Length - weight r e l a t i o n s h i p 63 R e l a t i v e growth 64 Depth d i s t r i b u t i o n 75 Food h a b i t s 80 DISCUSSION 84 SUMMARY 91 BIBLIOGRAPHY 94 i i i LIST OF TABLES page Table 1 Col lec t ions examined 5 Table 2 Limnological data and f i s h complement of four B r i t i s h Columbia lakes 11 Table 3 Range of mer i s t i c counts i n s i x species of Prosopium 18 Table 4 Frequency d i s t r i b u t i o n of l a t e r a l l i n e scale counts i n Prosopium c o u l t e r i 20 Table 5 Frequency d i s t r i b u t i o n of p y l o r i c caeca counts i n Prosopium c o u l t e r i 21 Table 6 Frequency d i s t r i b u t i o n of g i l l raker counts i n Prosopium c o u l t e r i 22 Table 7 Frequency d i s t r i b u t i o n of pectoral and p e l v i c ray counts i n Prosopium c o u l t e r i 23 Table 8 Frequency d i s t r i b u t i o n of dorsal and anal ray counts i n Prosopium c o u l t e r i 24 Table 9 Frequency d i s t r i b u t i o n of ver tebra l counts i n Prosopium c o u l t e r i 25 Table 10 Means of mer i s t i c counts for various populations of Prosopium c o u l t e r i 27 Table 11 Length d i s t r i b u t i o n of age groups of Cluculz Lake Prosopium c o u l t e r i 34 Table 12 Length d i s t r i b u t i o n of age groups of Tacheeda Lake Prosopium c o u l t e r i 35 Table 13 Length d i s t r i b u t i o n of age groups of MacLure Lake Prosopium c o u l t e r i 36 Table 14 Length d i s t r i b u t i o n of age groups of McLeese Lake Prosopium c o u l t e r i 37 i v Table 15 Calculated body - scale re la t ionsh ips for pygmy whi t e f i sh from f ive B r i t i s h Columbia lakes 46 Table 16 Calculated t o t a l length at end of each year of l i f e of each age group and average growth for the combined age groups i n Cluculz Lake . . . . 48 Table 17 Calculated t o t a l length at end of each year of l i f e of each age group and average growth for the combined age groups i n Tacheeda Lake . . . 49 Table 18 Calculated t o t a l length at end of each year of l i f e of each age group and average growth for the combined age groups i n MacLure Lake . . . . 50 Table 19 Calculated t o t a l length at end of each year of l i f e of each age group and average growth for the combined age groups i n MacLure Lake . . . . 51 Table 20 Mean fork length i n centimeters and instantaneous annual growth rates of pygmy whi t e f i sh i n four B r i t i s h Columbia lakes 56 Table 21 Age at maturity of pygmy whi te f i sh i n four B r i t i s h Columbia lakes 62 Table 22 Data r e l a t i n g measurements of various body parts to standard length for four B r i t i s h Columbia lakes 67 Table 23 Depth d i s t r i b u t i o n and catch of pygmy whi te f i sh i n MacLure and McLeese lakes during summer 1962 76 Table 24 Depth d i s t r i b u t i o n and catch of pygmy whi te f i sh i n Cluculz and Tacheeda lakes during summer 1962 77 Table 25 Stomach contents of pygmy whi te f i sh from four B r i t i s h Columbia lakes expressed as estimated percentage of t o t a l volume. A l l f i s h taken i n 1962 ...T 82 V LIST OF FIGURES page F i g u r e 1 Diagram of eye measurement 8 F i g u r e 2 Contour map of C l u c u l z Lake 12 F i g u r e 3 Contour map of McLeese Lake 13 F i g u r e 4 Contour map of MacLure Lake 14 F i g u r e 5 Contour map of Tacheeda Lake 15 F i g u r e 6 Map of B . C . showing l o c a t i o n of the f o u r s tudy lakes 16 F i g u r e 7 L a t i t u d i n a l v a r i a t i o n i n a n a l r a y s , p e c t o r a l r a y s , and l a t e r a l l i n e s ca le s i n Prosopium  c o u l t e r i 30 F i g u r e 8 L a t i t u d i n a l v a r i a t i o n i n v e r t e b r a e , g i l l r a k e r s and p y l o r i c caeca i n Prosopium c o u l t e r i . . 31 F i g u r e 10 Diagram i l l u s t r a t i n g s c a l e measurements used . . . . 38 F i g u r e 11 R e l a t i o n of a n t e r o - l a t e r a l r i d g e s c a l e measurement t o f o r k l e n g t h i n Kinbasket Lake f i s h , 39 F i g u r e 12 R e l a t i o n of a n t e r i o r r a d i u s s c a l e measurement t o f o r k l e n g t h i n Kinbasket Lake f i s h 39 F i g u r e 13 R e l a t i o n of a n t e r i o r r a d i u s s c a l e measurement t o f o r k l e n g t h i n Kinbasket Lake and C l u c u l z Lake f i s h 40 F i g u r e 14 R e l a t i o n s h i p of s c a l e l e n g t h t o f o r k l e n g t h i n Kinbasket Lake pygmy w h i t e f i s h 42 F i g u r e 15 R e l a t i o n s h i p of s c a l e diameter to f o r k l e n g t h - i n Kinbasket Lake pygmy w h i t e f i s h 42 v i Figure 16 Relat ionship of scale diameter to fork length i n Tacheeda Lake pygmy whi te f i sh 43 Figure 17 Relat ionship of scale diameter to fork length i n Cluculz Lake pygmy whi te f i sh 43 Figure 18 Relat ionship of scale diameter to fork length i n McLeese Lake pygmy whi te f i sh 44 Figure 19 Relat ionship of scale diameter to fork length i n MacLure Lake pygmy whi te f i sh 45 Figure 20 Relat ionship of scale diameter to fork length i n Lake Superior pygmy whi t e f i sh 52 Figure 21 Calculated length at end of each year of growth for Cluculz Lake pygmy whi te f i sh ( s o l i d l i n e - females; broken l i ne i males) 53 Figure 22 Calculated length at end of each year of growth for Tacheeda Lake pygmy whi t e f i sh ( s o l i d l i n e - females; broken l i n e - males) 53 Figure 23 Calculated length at end of each year of growth for MacLure Lake pygmy whi te f i sh ( s o l i d l i n e - females; broken l i n e - males) 54 Figure 24 Calculated length at end of each year of growth for : McLeese Lake pygmy whi te f i sh ( s o l i d l i n e - females; broken line-males) 54 Figure 25 P lo t of instantaneous growth ra te against spec i f ied s ize for pygmy whi te f i sh i n four B r i t i s h Columbia lakes 57 Figure 26 Calculated length at end of each year of growth for female pygmy whi te f i sh i n four B r i t i s h Columbia lakes 59 Figure 27 Length-weight r e l a t ionsh ip of MacLure Lake pygmy whi te f i sh 65 v i i Figure 28 Relat ionship of predorsal length to standard length . 68 Figure 29 Relat ionship of head length to standard length 68 Figure 30 Relat ionship of body depth to standard length 69 Figure 31 Relat ionship of i n t e r o M t a l width to standard length 69 Figure 32 Relat ionship of o rb i t length to standard length . . . 70 Figure 33 Relat ionship of length of upper jaw to standard length 70 Figure 34 Relat ionship of length of dorsal f i n base to standard length 71 Figure 35 Relat ionship of length of anal f i n base to standard length 71 Figure 36 Relat ionship of height of anal f i n to standard length 72 Figure 37 Relat ionship of height of dorsal f i n to standard length 72 Figure 38 Relat ionship of length of pectoral f i n to standard length 73 Figure 39 Relat ionship of length of pe lv i c f i n to standard length 73 Figure 40 Depth d i s t r i bu t i ons of whi te f i sh i n four B r i t i s h Columbia lakes during Summer, 1962 78 INTRODUCTION The pygmy wh i t e f i sh , Prosopium c o u l t e r i (Eigenmann and Eigenmann), i s a small coregonine f i s h widely d i s t r i bu t ed throughout the lakes and r i ve r s of the North American C o r d i l l e r a from the Columbia River drainage northward to Alaska . In add i t i on , a r e l i c t population i s known to inhabi t Lake Superior (Eschmeyer and B a i l e y , 1 9 5 4 ) . Aside from a few populations i n the Columbia River bas in , the pygmy whi te f i sh of B r i t i s h Columbia has never been adequately described. The present study i s , i n pa r t , a descr ip t ion of mer i s t i c v a r i a t i o n w i th in the species i n B r i t i s h Columbia and a comparison of B r i t i s h Columbia f i s h wi th those of other areas. T y p i c a l l y , the pygmy whi t e f i sh i s character ized by a very slow growth ra te and small s i ze at maturi ty. There i s , however, w i t h i n the province of B r i t i s h Columbia, considerable d i s p a r i t y i n the s ize at maturity of f i s h from di f ferent populat ions. The s izes at ta ined by f i s h i n MacLure and McLeese Lakes great ly exceed those reported for any other populat ion. The major part of th i s study i s a comparison of the age and 2 growth of the MacLure and McLeese lake populations wi th the more t y p i c a l "pygmy" growth form of f i s h from Cluculz and Tacheeda Lakes. An attempt has been made to corre la te these differences i n growth rate wi th factors i n the phys ica l and b i o t i c environment. In add i t ion , the r e l a t i v e growth of body parts of f i s h i n the four populations has been analyzed to discover whether there ex i s t s any r e l a t ionsh ip between t h i s and growth r a t e . 3 MATERIALS AND METHODS F i e l d Data During the summer of 1962, pygmy whitefish were c o l l e c t e d i n four lakes i n B r i t i s h Columbia: Tacheeda Lake i n the MacKenzie River drainage; MacLure Lake i n the Skeena River drainage; and two lakes, Cluculz and McLeese, i n the Fraser River drainage basin. A l l f i s h were taken i n monofilament g i l l n e t s approximately f i f t y feet i n length. These were of two kinds: eight-foot deep nets ranging i n size from % inch to 2% inches, and twenty-five-foot deep nets of 1%, 2, and 2% inches stretch measure. Nets were f i s h e d at known depths f o r periods of from four to t h i r t y - s i x hours; generally about twelve hours. The approximate position of each f i s h i n the net was recorded at the time of removal. After being removed from the net, the f i s h were s l i t to hasten the preservation of stomach contents and then placed i n a forty per cent solution of formalin. 4 Other f i e l d data include temperature p r o f i l e s for each lake recorded at i r r egu la r in t e rva l s using an E lec t ron ic thermometer manufactured by Appl ied Research Associa tes , A u s t i n , Texas; and two ser ies of oxygen determinations made during August at MacLure and Cluculz Lakes. Counts and Measurements Counts and measurements were made af ter the f i s h had been.washed.and transferred to for ty per cent i sopropyl a l c o h o l . Specimens examined The specimens examined are from the co l l e c t i ons of the Ins t i tu t e of F isher ies Museum, Univers i ty of B r i t i s h Columbia, or are from as yet uncatalogued c o l l e c t i o n s made by the author during the summer of 1962 (the l a t t e r are designated by numbers pref ixed wi th the l e t t e r " s " ) . Col lec t ions which were examined i n whole or i n part are l i s t e d below i n Table 1. Counts The d e f i n i t i o n of various counts was that of Hubbs and Lagler (1957). Wherever necessary a binocular microscope was used as an a i d i n counting. a) l a t e r a l l i n e sca les . The count was terminated at the end of the hypural p l a t e , the pos i t i on of which was determined 5 by the crease formed when the t a i l of the f i s h was s h a r p l y bent . In most cases there were o n l y two or three l a t e r a l l i n e s c a l e s beyond t h i s p o i n t . Gaps where s c a l e s had been removed by g i l l net s t rands or o therwise l o s t were br idged by the enumeration of empty s c a l e p o c k e t s . Tab le 1. C o l l e c t i o n s examined C o l l e c t i o n Numbers L o c a l i t y A l a s k a Brooks Lake A l e k n a g i k Lake MacKenzie Drainage Dease Lake Tacheeda Lake Skeena Drainage MacLure Lake F r a s e r Drainage Moose Lake Yel lowhead Lake McLeese Lake C l u c u l z Lake Columbia R i v e r Drainage K i c k i n g Horse R i v e r B l aeb er ry R i v e r Kinbasket Lake L a i r d Creek Lake S u p e r i o r Keewenaw Bay BC 58 - 418 BC 60 - 399, BC 62 - 967 BC 56 - 477 S94, S95, S154, S177 S172A, S172B S69, S72, S179 BC 57 - 384 BC 57 - 385 BC 57 - 386 BC 57 - 390, BC 57 - 391 S83, S84, S86, S88, S89, S157, S160 S104, S143, S178 BC 56 BC 56 BC 56 BC 56 493 472 476 189 BC 55 - 387 BC 57 - 416 6 b) g i l l rakers . Counts were made of a l l g i l l rakers , inc lud ing rudimentary ones, on the f i r s t arch on the l e f t s ide . In a l l but a few cases i t was not necessary to remove the g i l l a rch. c) p y l o r i c caeca. Because of the small number of caeca found i n i n d i v i d u a l f i s h , i t was not necessary to remove each caecum at the time of enumeration. The d iges t ive t rac t was severed jus t an ter ior to the stomach and then removed from the body cav i ty for examination. The d iges t ive t rac t was l e f t attached at i t s poster ior end to prevent i t s separation from the specimen. d) dorsal and anal rays . A l l an ter ior unbranched rays were included i n th i s count. The l a s t double ray , d ivided near the base, was counted as one. e) vertebrae. A l l ver tebra l counts were made from X-ray negatives produced by a General E l e c t r i c Model "D" machine us ing Type "M" Indus t r i a l Kodak f i l m . Exposures averaged about 1600 mill iampere seconds at a distance of f i f t y - f i v e inches. The hypural vertebrae were included i n the counts. P la te 14, Diagram H i n Norden (1962) was used as a guide. f) pec tora l and p e l v i c rays . Although both l e f t and r i g h t f in s were counted, the two d id not appear to d i f f e r s i g n i f i c a n t l y and only the counts for the l e f t pec tora l and l e f t p e l v i c f in s are included here. A l l rays , branched and unbranched, were counted. 7 Measurements Measurements of standard length and various body parts were made to the nearest tenth of a mi l l imete r using a pa i r of d i a l - r ead ing c a l i p e r s . In a few cases, where the standard length of a f i s h exceeded the 200 mm capacity of the c a l i p e r s , measurements were made wi th d iv iders and a r u l e . A l l measurements were made exact ly as described i n Hubbs and Lagler (1957). The exceptions were: a) body depth. This measurement was taken as the distance from the anter ior base of the dorsal f i n to the anter ior base of the p e l v i c f i n . This was done so as to el iminate discrepancies a r i s i n g from d is ten t ion due to expansion of the swim bladder or from s l i t t i n g . b) length of eye. The length of the eye was measured as indica ted i n Figure 1. This measurement i s the midl ine distance from the pos ter ior margin of the eyebal l to the an te r ior f o l d of the v e s t i g i a l adipose eye l id (as i d e n t i f i e d by K. W. Stewart, personal communication). I t was f e l t that t h i s method of measurement would give more e a s i l y reproducible r e su l t s than the usual measurement of length of o r b i t . Measurements were a lso made of the height of the dorsal and anal f i n s . The length of the dorsal and anal base, the length of the l e f t pec tora l and p e l v i c f i n s , head length, i n t e r -o r b i t a l width , predorsal length, and length of the upper jaw. A N T E R I O R FOLD OE ADIPOSE E Y E L I D Figure 1. Diagram of eye measurement Age and Growth A l l fork lengths, weighs, and scale samples were taken from preserved f i s h . Sex and state of maturity were determined at the same time. Fork lengths were determined us ing a measuring board. The scales were removed from an area l y i n g between the dorsal f i n and the l a t e r a l l i n e . The scales were then cleaned by gentle scraping and sandwiched between two s l i des which were then taped together. Scales mounted i n t h i s way have been kept 9 for as long as nine months without showing any signs of drying, c rack ing , or w r i n k l i n g . Measurements of annul i were made at a magnificat ion of X43.8 us ing and Bausch and Lomb s l i d e projec tor . A simple nomograph was used i n back c a l c u l a t i o n . Food Studies The amounts of various food items present i n the die ts of pygmy whi te f i sh were determined by emptying the contents of the stomachs in to a squared p e t r i d i s h . The food items were then separated in to groups and a v i s u a l estimate recorded of the r e l a t i v e proportions of the various foods represented. Because of the small s i ze of most stomach samples, the contents of from f ive to ten stomachs were combined i n making the estimate. Only the stomachs of large MacLure Lake f i s h were examined i n d i v i d u a l l y . The Habitat Table 2 presents the ava i lab le p h y s i c a l , chemical, and b i o l o g i c a l data for each of the four lakes . Figures 2 to 5 i l l u s t r a t e the contour cha rac te r i s t i c s of the lakes and the main ne t t ing areas. Their geographical pos i t ion i s shown i n Figure 6. None of the lakes has been the subject of in tens ive l imnolog ica l i nves t i ga t i on . The lakes f a l l i n to two groups. Tacheeda and Cluculz are both r e l a t i v e l y deep lakes wi th a low to moderate content of 1 0 disso lved s o l i d s (TDS). This f i s h fauna i s dominated by salmonid species (seven i n Cluculz Lake and s i x i n Tacheeda). The other two lakes , McLeese and MacLure, are smaller , shallower, and have considerably higher TDS values. In each case only two salmonids are present, Salmo gai rdner i and Prosopium c o u l t e r i . Northcote and L a r k i n (1956) have demonstrated a s i g n i f i c a n t r e l a t ionsh ip between lake produc t iv i ty and t o t a l d issolved s o l i d content of B r i t i s h Columbia lake waters. Lake p roduc t iv i ty was shown to increase wi th increasing TDS. F i e l d observations would indica te that the i r general iza t ion holds true i n th i s case and that Cluculz and Tacheeda are indeed less productive than McLeese and MacLure. Within the groups, Tacheeda appears to be less productive than Cluculz and McLeese less productive than MacLure. Data are meagre, however, and th i s ranking i s la rge ly subject ive . 11 Tab le 2 . L i m n o l o g i c a l data and f i s h complement of f o u r B r i t i s h Columbia lakes CLUCULZ MACLURE MCLEESE TACHEEDA E l e v a t i o n Maximum Depth Mean Depth T o t a l D i s s o l v e d S o l i d s Surface Area 2500 200' 97 ' 118 ppm 1800' 73 ' 3 6 . 4 ' 208 ppm 2400' 152' 5 3 . 6 ' 250 ppm 2382' 195' 5 7 . 4 ' 52 ppm 6223 acres 785 acres 841 acres 1460 Trout and Char S a l v e l i n u s namaycush x x S. malraa x x Salmo g a i r d n e r i x x x x Oncorhynchus nerka x W h i t e f i s h Prosopium c o u l t e r i x x x x P . w i l l i a m s o n i x x Coregonus c lupea formis x x Suckers Catostomus macroche i lus x x C. commersoni x x C. catestomus x x x x Minnows R i c h a r d s o n i u s b a l t e a t u s x x x x P t y c h o c h e i l u s oregonensis x x x x M y l o c h e i l u s caurinum x x x x S c u l p i n s Cottus asper x x x Burbot L o t a l o t a x x CLUCULZ L A K E N S C A L E :1IN.= 6612 F T O NETTING A R E A Figure 2 . Contour map of Cluculz Lake McLEESE LAKE Figure 3. Contour map of McLeese Lake SCALE :1IN.= 2000 FT. ONETTING AREA MAC LURE L A K E Figure 4 . Contour map of McLure Lake SCALE: I IN= 2000 FT. ONETTING A R E A TACHEEDA LAKE N SCALE:IIN.= 3200 FT. O N E T T I N G A R E A Figure 5. Contour map of Tacheeda Lake Figure 6 Map of B r i t i s h Columbia showing loca t ion of the four study lakes 17 RESULTS Meristics Whitefishes (Coregonidae) are notorious for the high degree of meristic v a r i a b i l i t y found within and between populations of the same species. In t h i s respect the species making up the genus Prosopium are not d i f f e r e n t from others. The meristic counts of the s i x species of Prosopium are compared i n Table 3. Of the s i x , three (P. spilonotus, P. gemmiferum, and P. abyssicola) are endemic to Bear Lake, Idaho and Utah, and presumably constitute single, homogeneous populations. The samples counted were small (Snyder, 1919). For these reasons the small range of counts i s not unexpected. The other three species, which range over a much wider area, show considerable v a r i a b i l i t y . In general, pygmy species of a group tend to have fewer parts than c l o s e l y r e l a t e d larger fishes. Barlow (1961) has demonstrated a reduction i n the number of f i n rays and scales i n a dwarf species of the goby G i l l i c h t h y s . Myers (1958), generalizing about fishes of minute s i z e , notes, among other Table 3. Range of mer i s t i c counts i n s i x species of Prosopium WILLIAMSONI SPILONOTUS CYLINDRACEUM ABYSSICOLA GEMMIFERUM COULTERI Holt (1960) Snyder(1917) J .D.McPhai l (pers.comm.) Snyder(1917) Snyder(1917) This study Number of Specimens 357 22 8 + 4 + 1 0 10 10 229 L a t e r a l l i n e scales 73 - 92 74 - 81 83 - 107 69 - 76 71 - 77 50 - 72 G i l l rakers 17 - 25 18 - 22 14 - 21 18 - 23 4 1 - 4 4 12 - 20 P y l o r i c caeca 50 - 146 135..- 140 50 - 130 73 - 78 81 - 86 13 - 33 Dorsal rays 11 „ 14 1 0 - 1 2 13 15 10 - 11 9 - 1 1 10 - 13 Anal rays 10 - 13 9 - 1 1 11 - 13 9 - 11 11 - 12 10 - 14 Vertebrae 53 - 61 59 - 65 50 - 55 Pec tora l rays 14 - 18 13 - 18 CO 19 trends, a reduction i n the number of scales and a s i m i l a r but less s t r i k i n g reduction i n the number of f i n rays . Of the s i x species, P. c o u l t e r i i s dis t inguished by i t s small number of l a t e r a l l i n e scalels, g i l l rakers , and, most important i n the opinion of Eschmeyer and Bai ley (1954), i t s very low p y l o r i c caeca count. Although counts of vertebrae are not ava i l ab le for the three Bear Lake whi tef ishes , i t i s not u n l i k e l y that the low numbers cha rac t e r i s t i c of pygmy whi t e f i sh are a l so d i s t i n c t i v e . The numbers of f i n rays do not appear to be s i g n i f i c a n t l y di f ferent from those of other species . The only review of mer i s t i c v a r i a t i o n i n Prosopium  c o u l t e r i i s Eschmeyer and B a i l e y ' s 1954 paper repor t ing the discovery of a r e l i c t population of the f i s h i n Lake Superior at a distance of over 1100 miles from the nearest population i n the Columbia River bas in . The authors did not examine B r i t i s h Columbia f i s h from outside of the Columbia River system and there i s , consequently, a considerable hiatus i n t h e i r discussion of geographic v a r i a t i o n from southern B r i t i s h Columbia to Alaska . This work presents counts for add i t i ona l Columbia populations as w e l l as data for f i s h from the Fraser , Skeena and Mackenzie basins i n B r i t i s h Columbia. In add i t i on , counts were made on pygmys from Brooks Lake and Lake Alegnagik, Alaska , and Lake Superior. These counts are presented i n tables 4 to 9. In every case, an analys is of variance indicates a s i gn i f i c an t difference between the means of the populations (the F values are included wi th the t a b l e s ) . Table 4 . Frequency d i s t r i b u t i o n of l a t e r a l l i n e s c a l e counts i n Prosopium c o u l t e r i T n „ A T T n H LATERAL LINE SCALES L U U U I U N - 5 0 5 1 5 2 5 3 5 4 5 5 5 6 5 ? 5 g 5 Q 6 Q 6 1 6 2 63 64 65 66 67 68 69 70 71 N Mean SD Brooks Lake — 1 3 2 2 4 3 3 1 1 — 20 54.85 2.21 MacKenzie Drainage Dease Lake — 1 1 — 3 2 3 4 2 — 1 — 1 - 20 56.10 2.62 Tacheeda Lake 1 — 1 1 3 4 4 1 2 1 2 — 20 57.65 3.56 Skeena Drainage MacLure Lake — - 2 3 2 2 3 2 2 4 20 61.75 2.45 F r a s e r Drainage Moose Lake 1 1 1 — 1 4 1 1 3 5 — 1 1 20 61.60 3.22 Yel lowhead Lake 1 — 2 1 — 2 — 2 2 1 11 57.09 2.98 McLeese Lake 1 1 1 2 1 5 6 1 1 — 1 - 20 54.95 2.33 C l u c u l z Lake — 1 — 2 2 1 — 2 1 2 3 3 2 2 2 22 58.59 3.91 Columbia Drainage K i c k i n g Horse R. 1 — 1 1 5 — 2 1 — 1 — 12 61.75 2.95 B l a e b e r r y R i v e r 1 1 1 2 — 3 3 2 - - 1 2 — 1 2 — 1 20 62.90 4 .16 K inbaske t Lake — — 1 — 1 — 1 4 5 2 2 2 1 1 20 60.25 2.59 L a i r d Creek 1 4 2 3 2 3 2 1 1 1 20 57.80 2.54 O Table 5. Frequency d i s t r i b u t i o n of p y l o r i c caeca counts i n Prosopium c o u l t e r i PYLORIC CAECA 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 N Mean SD LOCALITY Alaska Brooks Lake 7 4 2 2 4 1 20 17.90 2.13 MacKenzie Drainage Dease Lake 2 6 2 3 2 1 1 3 — 20 19.95 2.25 Tacheeda Lake 1 3 1 3 7 4 — 1 - 20 21.20 2.46 Skeena Drainage MacLure Lake 3 2 2 3 2 4 4 20 19.35 2.16 Fraser Drainage Moose Lake 1 1 1 3 4 2 6 1 — 1 20 21.50 2.14 Yellowhead Lake 1 — 3 1 3 1 — 1 1 11 19.27 3.13 McLeese Lake — 4 1 1 2 1 2 - 11 16.09 2.02 Cluculz Lake — 1 1 5 3 2 1 — 4 1 1 19 20.10 3.07 Columbia Drainage K i c k i n g Horse R. 2, — — 1 1 4 1 - 1 — 1 — — 1 12 23.50 4.12 Blaeberry River 1 — 1 4 5 — 4 3 1 1 : - 20 20.85 2.35 Kinbasket Lake 1 4 4 3 3 2 — 1 1 19 21.95 2.32 L a i r d Creek 1 2 1 2 1 3 1 2 2 1 — 2 1 1 — — — 20 23.05 3.85 Table 6. Frequency d i s t r i b u t i o n of g i l l raker counts i n Prosopium c o u l t e r i T nriTTTV GILL RAKERS U A A L i i Y 12 13 14 15 16 17 18 19 20 N Mean SD Alaska Brooks Lake - - 1 12 5 1 - - 19 16.32 0.66 MacKenzie Drainage Dease Lake — — — — 2 9 7 1 1 20 17.50 0.95 Tacheeda Lake 2 12 4 2 — - - -> 20 14.30 0.78 Skeena Drainage MacLure Lake 1 12 7 - - — — — 20 14.30 0.56 Fraser Drainage Moose Lake 2 9 2 6 1 20 13.75 1.17 Yellowhead Lake — 2 8 1 11 13.90 0.55 McLeese Lake — — 7 10 3 - 20 15.80 0.69 Cluculz Lake 1 8 8 2 1 — — — 20 13.70 0.92 Columbia Drainage K i c k i n g Horse R. 1 4 5 1 1 — 12 14.66 1.24 Blaeberry River —. 3 11 6 — - - — - - 20 14.15 0.69 Kinbasket Lake 3 4 11 2 — -~ 20 13.60 0.89 L a i r d Creek — 1 7 9 3 — ~ 20 . 15.70 0.79 F = 41.76 : ' ;  to ro Table 7. Frequency d i s t r ibu t ions of pectoral and p e l v i c ray counts i n Prosopium c o u l t e r i LOCALITY LEFT PECTORAL RAYS 13 14 15 16 17 18 N Mean SD LEFT PELVIC RAYS 9 10 11 N Mean SD Alaska Brooks Lake 5 7 7 1 — 20 15.20 0.89 5 15 — 20 9.75 0.46 MacKenzie Drainage Dease Lake 8 12 20 13.60 0.51 1 19 20 9.95 0.23 Tacheeda Lake 1 7 7 5 - - 20 15.80 0.88 4 16 — 20 9.80 0.40 Skeena Drainage MacLure Lake 1 13 6 -- — 20 15.25 0.56 — 15 5 20 10.25 0.46 Fraser Drainage 0.40 Moose Lake 6 14 _ _ - - 20 15.70 0.51 2 17 1 20 9.95 Yellowhead Lake — 3 8 — 11 15.27 0.45 1 10 _ _ 11 9.91 0.32 McLeese Lake 7 12 1 20 14.70 0.56 4 16 __ 20 9.80 0.40 Cluculz Lake — 6 11 2 - - 19 15.79 0.62 2 17 1 20 9.95 0.40 Columbia Drainage Kick ing Horse R. — 2 6 4 _«. 12 15.17 0.74 6 6 _ - 12 9.50 0 .52 Blaeberry River - - 1 13 5 1 — 20 15.30 0.69 5 15 — 20 9.75 0.46 Kinbasket Lake _ _ 13 6 1 — 20 15.40 0.61 1 18 1 20 10.00 0.32 L a i r d Creek 1 — 6 7 6 20 16.85 1.05 2 16 2 20 10.00 0.46 F = 23.000 r o Table 8. Frequency d i s t r i bu t ions of dorsal and anal f i n ray counts i n Prosopium c o u l t e r i DORSAL FIN RAYS 10 11 12 13 'N Mean LOCALITY SD ANAL FIN RAYS 10 11 12 13 14 N Mean SD Alaska Brooks Lake 5 10 5 -- 20 11.00 0.73 — 4 10 6 -- 20 12.10 0.73 MacKenzie Drainage Dease Lake 5 13 2 _ _ 20 10.85 0.61 — 15 5 20 11.25 0.46 Tacheeda Lake — 8 12 — 20 11.61 0.51 — 3 10 7 — 20 12.20 0.68 Skeena Drainage 0.46 MacLure Lake 1 16 3 — 20 11.10 0.46 — 6 14 -- 20 11.70 Fraser Drainage 0.83 Moose Lake _ _ 5 14 1 20 11.80 0.56 — 1 7 9 3 20 12.70 YeUowhead Lake 1 3 6 1 11 11.64 0.84 1 — 2 8 _ _ 11 12.54 0.95 McLeese Lake 7 11 2 20 11.75 0.65 — 6 10 4 —— 20 11.90 0.73 Cluculz Lake — 17 3 — 20 11.85 0.40 — 11 7 2 20 12.55 0.69 Columbia Drainage 0.74 Kick ing Horse R. 5 7 12 11.58 0.52 — 3 6 3 12 12.00 Blaeberry River 6 14 20 11.70 0.51 — 4 13 3 _ — 20 11.95 0.61 Kinbasket Lake _ _ 2 15 3 20 12.05 0.51 8 11 1 20 12.65 0.61 L a i r d Creek 1 . 10 8 1 20 11.45 0.69 — — 3 11 6 20 13.15 0.69 F = 6.94 F = 10.87 r o 4> Table 9. Frequency d i s t r ibu t ions of ver tebral counts i n Prosopium c o u l t e r i LOCALITY 50 51 52 53 VERTEBRAE 54 55 N Mean SD Alaska Brooks Lake 1 10 7 2 -- -- 20 51.50 0.76 MacKenzie Drainage Dease Lake _ _ 5 15 20 51.75 0.46 Tacheeda Lake — 7 9 3 — 19 51.79 0.71 Skeena Drainage MacLure Lake — 2 10 5. 3 — 20 52.45 0.89 Fraser Drainage 0.83 Moose Lake 4 9 6 1 20 53.20 Yellowhead Lake 1 2 4 4 w _ 11 52.00 1.00 McLeese Lake _ _ 1 10 9 _ _ 20 52.40 0.61 Cluculz Lake -- 2 8 6 4 20 52.60 0.95 Columbia Drainage 53.33 Kick ing Horse River _ _ 1 6 5 12 0.67 Blaeberry River _ — 2 17 1 20 52.95 0.40 Kinbasket Lake 4 4 8 4 20 52.60 1.05 La i rd Creek 1 3 9 7 - - — 20 52.10 0.86 F = 9.67 26 A notab le f e a t u r e of the m e r i s t i c c h a r a c t e r s of Prosopium c o u l t e r i i s the extreme ranges of counts even w i t h i n a s i n g l e p o p u l a t i o n . In the B l a e b e r r y R i v e r sample, f o r i n s t a n c e , there was a twenty-n ine per cent d i f f e r e n c e between the lowest and h ighes t numbers of l a t e r a l l i n e s c a l e s . In the K i c k i n g Horse R i v e r f i s h , there was a d i f f e r e n c e of f o r t y - o n e per cent and e i g h t y - t h r e e per cent r e s p e c t i v e l y between the lowest and h ighes t g i l l r a k e r and p y l o r i c caeca counts . The d i f f e r e n c e between p o p u l a t i o n s i s , of c o u r s e , even g r e a t e r : f o r t y - t w o per cent f o r l a t e r a l l i n e s c a l e s ; s i x t y - s i x per cent f o r g i l l r a k e r s ; and 151 per cent f o r p y l o r i c caeca . Thus, the s i z e of the sample i s s m a l l i n comparison w i t h the v a r i a t i o n . In most cases the range of counts of any one c h a r a c t e r f o r a s i n g l e p o p u l a t i o n over laps the means of a l l p o p u l a t i o n s . As a r e s u l t , w i t h o u t l a r g e r samples from each l o c a l i t y , any c o n c l u s i o n s based on a comparison of means can o n l y be t e n t a t i v e l y accepted . Where p o s s i b l e , a t l e a s t twenty i n d i v i d u a l s from e a c h p p u l a t i o n were counted. C o n s i d e r i n g t h a t a l l toge ther o n l y seventeen p o p u l a t i o n s are represented spread over a t h i r d of Nor th A m e r i c a , the t e n u i t y of any c o n c l u s i o n s i s even more obv ious . Table 10 presents the means f o r s e v e r a l m e r i s t i c c h a r a c t e r s of seventeen p o p u l a t i o n s . F igure s f o r f i v e of these p o p u l a t i o n s have been taken i n whole or i n pa r t from Eschmeyer and B a i l e y (1954) . These are i n d i c a t e d by an a s t e r i s k ( * ) . Only means of samples of ten f i s h or more are i n c l u d e d . (Means f o r the p e c t o r a l and p e l v i c rays were a r r i v e d a t by h a l v i n g t h e i r f i g u r e s which t o t a l l e d the l e f t and r i g h t f i n s ) . The Table 10. Means of mer i s t i c counts for various populations of Prosopium c o u l t e r i LOCALITY LAT°N LONG MAT LLS GR PC VERT DR AR PlR ? 2 R Alaska Brooks Lake 58 157 30-35 54.85 *Aleknagik Lk 60 159 30-35 61.77 *Chignik Lk 56 159 30-35 63.75 MacKenzie River Drainage Dease Lake 59 130 30-35 56.10 Tacheeda Lake 55 123 30-35 57.65 16.32 17.90 13.70 23.00 14.56 17.50 14.30 19.95 21.20 51.50 11.00 12.10 52.57 11.12 11.70 11.56 12.75 51.75 10.85 11.25 51.79 11.61 12.20 15.20 9.75 14.75 9.85 15.19 9.64 13.60 9.95 15.80 9.80 Skeena River Drainage MacLure Lake 55 127 35-40 61.75 14.30 19.35 52.45 11.10 11.70 15.25 10.25 Fraser River Drainage Cluculz Lake 54 123 35-40 58.59 13.70 20.10 52.60 11.85 12.55 15.70 9.95 Moose Lake 53 120 35-40 61.60 13.75 21.50 53.20 11.80 12.70 15.70 9.95 Yellowhead 53 119 35-40 57.09 13.90 19.27 52.00 11.64 12.54 15.27 9.91 McLeese Lake 53 122 40-45 54.95 15.80 16.09 52.40 11.75 11.90 14.70 9.80 Columbia River Drainage Kinbasket R 52 118 35-40 60.25 13.60 21.95 52.60 12.05 12.65 15.40 10.00 Blaeberry R 52 118 35-40 62.90 14.15 20.85 52.95 11.70 11.95 15.30 9.75 K i c k i n g Horse 51 117 35-40 61.75 14.66 23.50 53.33 11.85 12.00 15.17 9.50 L a i r d Creek 50 117 40-45 57.80 15.70 23.05 52.10 11.45 13.15 16.85 10.00 * B u l l Lake 49 116 40-45 60.70 16.71 11.83 12.57 15.89 9.88 *Lake MacDonald 49 114 40-45 59.20 17.20 11.40 12.54 16.00 9.67 *Lake Superior 48 87 35-40 57.14 18.20 17.60 53.09 10.90 13.20 14.62 10.28 * Counts wholly or pa r t ly from Eschmeyer and Bai ley (1955) M.A.T. Mean Annual Temperature N> 28 table a l so includes the approximate l a t i tude and longitude of the l o c a l i t y and the range of mean annual temperature. Mean annual temperature was chosen to represent c l i m a t o l o g i c a l condit ions f i r s t , because the wide geographic spread of samples must i nev i t ab ly mean considerable va r i a t i on i n developmental rates and hatching times; and secondly, because the exact period at which various mer i s t i c ser ies are l a i d down i n pygmy whi te f i sh i s unknown. Some, such as vertebrae, may be determined jus t p r i o r to hatching (as i n Salmo t r u t t a , Taning, 1952). On the other extreme, age group 0 f i s h may s t i l l be without scales toward the end of t he i r f i r s t summer of growth. Thus, temperature condit ions i n no one month would have a meaningful r e l a t i onsh ip to mer i s t i c va r i a t i on between populations. I f the means of various mer i s t i c characters are graphed against the l a t i tude of sample areas (F igs . 7, 8) there appears to be a general tendency toward an increase i n parts i n the more southerly populat ions. This tendency i s quite apparent i n the graphs for anal rays and vertebrae. I t may be present, but wi th a higher degree of sca t te r ing i n pec tora l ray and p y l o r i c caeca counts. The number of l a t e r a l l i n e scales seems to vary randomly wi th l a t i t u d e . F i n a l l y , the r e l a t i o n between g i l l rakers and l a t i tude would appear to be a V-shaped curve wi th the greatest numbers of rakers at the extremes of l a t i tude and low counts i n the middle of the geographic range. Various authors have reported l a t i t u d i n a l c l i ne s of mer i s t i c counts i n f i shes . Jordan (1891) and Hubbs (1925) both reported that northern fishes generally possess more vertebrae than r e l a t ed , more southerly forms. Since then, numerous other 29 examples have been documented i n v o l v i n g ve r tebrae and o ther m e r i s t i c c h a r a c t e r s . L indsey (1953) and W e i s e l (1955) f o r the r e d s i d e s h i n e r , Taning (1952) f o r Salmo t r u t t a and Seymour (1959) f o r Oncorhynchus tshawytscha are examples. Exper imenta l work has shown that m e r i s t i c s e r i e s vary as the r e s u l t of the i n t e r a c t i o n of both genotypic and phenotypic components. The r e l a t i o n between m e r i s t i c counts and temperature i s most f r e q u e n t l y V-shaped w i t h the h i g h e s t or lowest counts at moderate temperatures (Tan ing , 1952, f o r Salmo t r u t t a ) , but as L indsey (1962) p o i n t e d o u t : "Demonstrat ion of V-shaped r a t h e r than s imple d i r e c t or i n v e r s e r e l a t i o n s h i p s between m e r i s t i c counts and temperature sometimes r e q u i r e s r e a r i n g at extremes c l o s e t o the upper or lower temperature t o l e r a n c e s of the s p e c i e s . The i n f l e c t i o n i n the curve may not be d i s c o v e r e d i f a narrower range of temperatures i s u s e d . " Other environmenta l f a c t o r s can a l s o i n f l u e n c e m e r i s t i c count s : s a l i n i t y , l i g h t i n t e n s i t y , oxygen and carbon d i o x i d e t ens ions have a l l been s t u d i e d and shown t o a f f e c t the fo rmat ion of p a r t s , presumably by v a r y i n g the r a t e of metabol i sm. Most of these vary w i t h l a t i t u d e and any one, or a l l of them might be the cause of a l a t i t u d i n a l c l i n e . However, temperature i s u s u a l l y c o n s i d e r e d t o be the most impor tan t . N o t i c e that the n o r t h e r n -most samples do come from the areas w i t h the lowest mean annual temperatures . The southern p o p u l a t i o n s , on the o ther hand, have the h i g h e s t mean annual temperatures . 30 13 12 CO 111 Q_ O 17 S16 LU < LU > 60 55 ANAL RAYS o ° o 0 0 0 o 0 o o o o ) 0 J 0 o o 1 1 1 I 1 . - 1 1 1 1 1 1 1 1 J PECTORAL RAYS - o -0 0 o 8 O o » o o o 8 o o o 1 1 1 1 1 . 1 1 1 1 ' ' « —' -LATERAL LINE SCALES o o 0 o 0 o o o 0 0 0 0 o 0 o 1 1 1 1 1 1 o 1 1 1 I I 60 55 Q 50 45 LATITUDE N. F i g u r e 7. L a t i t u d i n a l v a r i a t i o n i n a n a l r a y s , p e c t o r a l r a y s , , and l a t e r a l l i n e s c a l e s i n Prosopium c o u l t e r i 3 1 53 52k cn h -£17| CD Z 1 5 LU I14 < 2A 22 20 18 16 VERTEBRAE o o — o o > 0 0 0 o _ o 0 0 0 o • I I I 1 1 1 1 1 1 1 1 1 GILL RAKERS 0 0 0 0 o 0 0 o 8 o o 0 -1 1 1 1 1 0 0 1 1 o 1 1 1 1 1 1 PYLORIC CAECA 1 0 0 0 o o 0 0 0 0 0 o J 1 1 1 1 I o 0 1 1 1 1 1 1 1 60 55 50 A5 LATITUDE °N. Figure 8. L a t i t u d i n a l v a r i a t i o n i n vertebrae, g i l l rakers , and p y l o r i c caeca i n Prosopium c o u l t e r i 32 I t i s u n l i k e l y that i n nature any one of these environmental factors approaches extreme l i m i t s and i n most cases only one limb of the V i s represented by geographical c l i n e s . In salmonids, the usual tendency i s for parts to increase wi th increas ing l a t i t u d e , toward the colder end of the range. The opposite trend seems to be cha rac t e r i s t i c of most mer i s t i c ser ies i n the pygmy wh i t e f i sh . The V-shaped re l a t ionsh ip of g i l l rakers and la t i tude i s except ional . I f t h i s V-shaped curve i s r e a l , i t may mean that g i l l raker numbers are more l a b i l e to environmental modif ica t ion than other mer i s t i c characters i n the pygmy white-f i s h . This i s i n cont radic t ion to Svardson's (1950, 1952) opinion that , i n wh i t e f i sh , g i l l rakers are least modified by environmental inf luences . On the other hand, the g i l l raker counts may be la rge ly gene t ica l ly determined and not the d i rec t r e su l t of differences i n environment. Svardson (1952) has demonstrated a r e l a t ionsh ip between body s ize mer i s t i c counts i n Swedish wh i t e f i sh . Comparing ninety-four populations of Coregonus he found that the number of scales along the body increased wi th the body s ize of the population and that whi t e f i sh populations wi th few g i l l rakers d i sp lay , on an average, a better growth than populations wi th numerous g i l l rakers . On the basis of ava i l ab le data no such r e l a t ionsh ip can be shown for any mer i s t i c series i n the pygmy wh i t e f i sh . Although MacLure Lake pygmys, the fastest growing, have high counts, McLeese Lake f i s h , which have the second largest adult weight, have one of the lowest scale counts. Seven populations have lower g i l l raker counts than MacLure Lake f i s h , eleven have fewer g i l l rakers than McLeese Lake f i s h . 33 Age and Growth Age and growth c a l c u l a t i o n s were made f o r a t o t a l of 437 f i s h : 155 from C l u c u l z Lake ; 144 from Tacheeda; 108 from MacLure; and 60 from McLeese. The f i s h were taken a t i r r e g u l a r i n t e r v a l s from May t o September, 1962. For most of the summer the sma l l e s t nets i n use were one i n c h s t r e t c h measure. A h a l f -i n c h net was a v a i l a b l e f o r on ly a s h o r t p e r i o d i n September. As a r e s u l t , very few f i s h of a l e n g t h l e s s than 100 mm were taken and none s m a l l e r than 75 mm. Numerous attempts a t beach s e i n i n g of young were u n s u c c e s s f u l , probably because the young, l i k e the a d u l t f i s h , occupy waters too deep f o r the u s u a l s e i n i n g methods. The f i s h t h a t were taken i n g i l l nets extended, w i t h the e x c e p t i o n of thos taken from MacLure Lake , over a very narrow range. The s i z e and age d i s t r i b u t i o n of the sample i s g iven i n Tables 11 to 14. The u s u a l techniques of b a c k - c a l c u l a t i o n r e q u i r e the use of a s c a l e measurement which has a l i n e a r r e l a t i o n s h i p t o the l e n g t h of the f i s h at a l l ages. Because young f i s h were absent from the g i l l net c o l l e c t i o n s , there was no proof t h a t l i n e a r r e g r e s s i o n s c a l c u l a t e d f o r o l d e r f i s h a p p l i e d e q u a l l y t o them. F o r t u n a t e l y , a s e r i e s of se ined c o l l e c t i o n s of pygmy w h i t e f i s h was a v a i l a b l e from Kinbasket Lake on the Columbia R i v e r . These f i s h ranged i n s i z e from 25 mm t o 122 mm. Measurements were made of s e v e r a l s c a l e dimensions i l l u s t r a t e d i n F i g u r e 10. Two of these measurements show an i n f l e c t i o n when the f i s h has a t t a i n e d a l e n g t h of about 100 mm. The i n f l e c t i o n i s Table 11. Length d i s t r i b u t i o n of age groups of Cluculz Lake Prosopium c o u l t e r i Age Group Length i n t e r v a l (cm) I I I I I I IV V VI M F M F M F M F M F M F 8.0 - 8.5 — 1 - - - -8.6 - 9.0 1 9.1 - 9.5 1 9.6 - 10.0 10.1 - 10.5 1 10.6 - 11.0 2 2 11.1 - 11.5 2 — 7 10 2 3 1 11.6 - 12.0 1 6 17 2 3 1 12.1 - 12.5 - - - - — 4 20 5 15 2 12.6 - 13.0 8 1 12 1 1 — 13.1 - 13.5 1 — 12 13.6 - 14.0 2 2 — 14.1 - 14.5 - 1 14.6 - 15.0 15.1 - 15.5 — — 1 2 1 15.6 - 16.0 - 1 To ta l Number 2 1 2 3 20 56 10 48 5 6 2 Average Length 9.2 8.1 11.3 11.0 11.6 12.1 11.6 12.7 12.2 14.2 — 15.6 Table 12. Length d i s t r i b u t i o n of age groups of Tacheeda Lake Prosopium c o u l t e r i Age Group Length In terva l (cm) I I I I I I IV V VI ; M F M F M F M F M F M F 7.0 — 7.5 7.6 - 8.0 1 1 8.1 - 8.5 2 3 1 8.6 — 9.0 — — 2 9.1 - 9.5 — — 1 -9.6 - 10.0 — 1 1 10.1 - 10.5 -•- 2 1 2 -10.6 - 11.0 — „ 1 9 1 7 — 1 11.1 - 11.5 2 1 19 — 7 11.6 - 12.0 15 — 6 12.1 - 12.5 2 — 15 — 2 12.6 - 13.0 2 4 — -13.1 - 13.5 1 13.6 - 14.0 - - — — 1 Tota l Number 2 3 7 15 3 45 0 31 0 7 0 1 Average Length 8.2 8.4 9.0 1.0.6. 10.8 1 1 . 4 . . — . . 1 2 . 0 . — 12.6 — 13.6 Table 13. Length d i s t r i b u t i o n of age groups of MacLure Lake Prosopium c o u l t e r i Age Group Length (cm) I I I I I I IV V VI VII V I I I IX i n t e r v a l M F M F M F M F M F M F M F M F M F 10.0- 11.0 — — 12 9 11.1- 12.0 — — 6 1 12.1-13.0 — — 1 1 13.1-14.0 — 4 3 14.1-15.0 — — 6 1 - -15.1-16.0 — — 1 — - -16.1-17.0 17.1-18.0 — 1 1 18.1-19.0 3 1 2 — 1 19.1-20.0 1 4 1 1 20.1-21.0 - - — 2 1 - - — — 1 21.1-22.0 7 4 22.1-23.0 2 1 — 1 2 - - - -23.1-24.0 3 — 1 1 2 24.1-25.0 - - - - 5 — 3 — — 25.1-26.0 - 3 - - 4 - - 2 26.1-27.0 - 1 27.1-28.0 - — 1 Tota l Number 0 30 15 4.. 8 14 9 1 10 4. 9 0 3 0 0 0 1 Ave Length — — 12.1 11.7 19.2 19.0 21.0 21.9 18.5 24.5 22.5 24.8 — 25.7 — - - — 27.1 CO ON 37 Table 14. Length d i s t r i t u b i o n of age groups of McLeese Lake Prosopium c o u l t e r i Age Group Length (cm) I I I H I IV V i n t e r v a l M F M F M F M F M F 10.0- 11.0 — 1 3 11.1- 12.0 — — 2 1 12.L-L3.0 - -13.1-14.0 14.1-15.0 5 4 15.1-16.0 3 19 - -16.1-17.0 — - - — — 3 10 17.1-18.0 3 1 18.1-19.0 - 1 19.1-20.0 1 — 3 Tota l number 0 0 3 4 11 36 1 1 0 4 Ave Length — — 11 .110 .9 15.3 15.8 17.8 19.4 — 19.4 most marked i n the an te ro - l a t e ra l r idge ( F i g . 11), but i s a lso present i n measurements of the an ter ior radius of the scale ( F i g . 12). The i n f l e c t i o n i n the anter ior radius i s more obvious i f the measurements of Cluculz Lake f i s h , which are la rger , are graphed along wi th those of the Kinbasket Lake samples ( F i g . 13). The superposit ion of data i n t h i s fashion i s subject to error as the scale size-body length re la t ionsh ips are probably not i d e n t i c a l i n the two populat ions, but i n th i s case the error i s probably small i n r e l a t i o n to the magnitude of the i n f l e c t i o n . The data can be interpreted as forming two l i n e s : one l i n e extends to about 100 mm and includes most of the Kinbasket Lake f i s h and the smallest f i s h from Cluculz Lake; and the second l i n e includes the majority of Cluculz f i s h and few largest Kinbasket Lake f i s h . Obviously, a regression l i n e ca lcu la ted for f i s h larger than 100 mm (most of the sample f i sh) would give an intercept for the scale size-body length r e l a t ionsh ip which would be far too high for smaller f i s h . For t h i s reason, nei ther anter ior radius nor an te ro - la te ra l r idge measurements were useful i n the back-ca lcu la t ion of growth. The i n f l e c t i o n i s probably due to changes i n r e l a t i v e growth coincident w i th the attainment of matur i ty . In both Cluculz and Kinbasket the f i s h spawn for the f i r s t time at the end of t h e i r t h i r d summer at a length of about 100 mm. As far as 39 Figure 11. Rela t ion of an te ro - l a t e ra l r idge scale measurement to fork length i n Kinbasket Lake f i s h 0 300 600 SCALE MEASUREMENT (mm.) XA 3.8 E . j j 1 0 -X I— o z LLl _ J _ 5 cr o Li_ -L 0 300 600 SCALE MEASUREMENTSm.)X43.8 Figure 12. Rela t ion of an ter ior radius scale measurement to fork length i n Kinbasket Lake f i s h 15 £ x i — CD Z LU _ o 10 • • • -. .V . *' ' ' :*•£*•:• *•* *• . «» »* * • •« .« .* X " * » " it*. * KINBASKET K M • CLUCULZ 1 1 1 i i 0 300 6 00 9 00 1200 1500 SCALE MEASUREMENT( mm.)XA3.8 Figure 13. Rela t ion of anter ior radius scale measurement to fork length i n Kinbasket Lake and Cluculz Lake f i s h o 41 the author i s aware, such i n f l e c t i o n s have not been previously described for wh i t e f i sh . Two other scale measurements, scale length and scale diameter, both showed a s t r a i g h t - l i n e re la t ionsh ip to body length (F igs . 14, 1 5) for Kinbasket Lake. D i f f i c u l t y i n i d e n t i f y i n g annul i along the pos ter ior margin i n older f i s h precluded the use of scale length, and scale diameter was therefore chosen as the best measurements for the purpose of back-ca lcu la t ion . The scale diameter - fork length re la t ionsh ip i s graphed for Tacheeda, C l u c u l z , McLeese and MacLure Lakes i n Figures 16 to 19. In the f i r s t three lakes , the sample f i s h concentrated i n a very small segment of the range over which growth occurred - - toward the upper l i m i t . Linear regression of scale diameter against fork length resu l ted i n an apparent intercept which, i n each case, was f e l t to be far too h igh . Presumably t h i s resu l ted from differences i n i n t r a - c l a s s and in t e r - c l a s s co r r e l a t i ons . The preponderance of f i s h from a few year classes seems to have biased the r e s u l t . The c lus te r s of points do, however, appear to be very nearly i n l i n e wi th the ca lcula ted regression for Kinbasket Lake data which includes a considerable range of s i z e s . The re la t ionsh ips are probably not i d e n t i c a l , but i n the absence of further data, the intercept ca lcula ted for Kinbasket Lake was used i n back-c a l c u l a t i n g the lengths of f i s h from the other three lakes . Because the MacLure Lake sample extended over a much broader length range, the ca lcula ted intercept i s probably quite r e l i a b l e and i t was used i n back-ca lcula t ion for the f i s h from the lake . 0 300 600 900 1200 S C A L E M E A S U R E M E N T (mm)X43.8 Figure 14.' Relat ionship of scale length to fork length i n Kinbasket Lake pygmy whi te f i sh E X 10 LU cn s o • ••• •J, • 0 300 600 900 1200 SCALE M E A S U R E M E N T S . ) X 4 3 . 8 Figure 15. Relat ionship of scale diameter to fork length i n Kinbasket Lake pygmy whi te f i sh Figure 16. Relat ionship of scale diameter to fork length i n Tacheeda Lake pygmy whi t e f i sh I l i l 1_ 0 300 600 900 1200 1500 SCALE MEASUREMENT (mm) X 43.8 Figure 17. Relat ionship of scale diameter to fork length i n Cluculz Lake pygmy whi te f i sh J 1 300 600 900 1200 1500 SCALE MEASUREMENT (mm.)Xao Figure 18. Relat ionship of scale diameter to fork length i n MacLeese r Lake pygmy whi te f i sh » i I I I I L_ 0 300 600 900 1200 1500 1800 2100 SCALE MEASUREMENT (mm.) X A3.8 Figure :_9, ' R e l a t i o n s h i p of s c a l e diameter t o f o r k l e n g t h i n MacLure Lake pygmy w h i t e f i s h 0 300 600 900 1200 1500 1800 2100 2400 SCALE MEASUREMENT (mm.) XA3.8 46 Table 15. C a l c u l a t e d body-sca le r e l a t i o n s h i p s f o r pygmy w h i t e f i s h from f i v e B r i t i s h Columbia lakes MacLure McLeese C l u c u l z Tacheeda Kinbaske t 0.010990 0.008544 0.005624 0.006734 0.007972 0.388788 2.004891 4.708823 3.788794 1.324125 1.313413 1.075486 0.635308 0.637988 0.539005 0.971181 0.854798 0.793345 0.838985 0.983139 Slope of Regres s ion L i n e I n t e r c e p t of Regre s s ion L i n e Standard E r r o r of Es t imate C o r r e l a t i o n Data r e l a t i n g to the body-sca le r e l a t i o n s h i p of pygmy w h i t e f i s h from the f i v e lakes i s g iven i n Table 15. The r e g r e s s i o n was m a c h i n e - c a l c u l a t e d from data obta ined f o r every s c a l e . Back-c a l c u l a t i o n was c a r r i e d out a c c o r d i n g t o the formula L+- - I L - I q L = I + -I S n o r J! = fn where L n i s the l e n g t h of the f i s h at the end of the N t n year of l i f e , I i s the i n t e r c e p t of the sca le-body r e l a t i o n s h i p , L t i s the l e n g t h of the f i s h at c a p t u r e , S t i s the diameter of the s c a l e a t the t ime of capture and S n i s the diameter of the s c a l e w i t h i n the N t h annulus . In p r a c t i c e the c a l c u l a t i o n was performed used a s imple nomograph. Eschmeyer and B a i l e y (1954) do not appear t o have used an i n t e r c e p t i n b a c k - c a l c u l a t i n g the growth of pygmy w h i t e f i s h i n Lake S u p e r i o r . They s t a t e that "Growth c a l c u l a t i o n s were by 47 d i rec t proport ion". (This i n sp i te of the fact that specimens from lake Superior i n the Ins t i tu te of F isher ies Museum do appear to exh ib i t an intercept i n the scale diameter - fork length r e l a t i onsh ip ( F i g . 2 0 ) ) . Van Oosten (1929) describes a t y p i c a l coregonine sca le . His descr ip t ion of the annulus was used as a guide i n the loca t ion and measurement of year marks i n the pygmy whi te f i sh under study. No year round samples are ava i lab le but during 1962 a l l f i s h showed evidence of new growth by the end of May, p l ac ing the termination of annulus formation somewhere at the end of A p r i l or ea r ly i n May. In general, annul i were not d i f f i c u l t to place. Exceptions were f ishes of advanced age i n which increments of growth were very small and annul i consequently very close together and f i s h from McLeese Lake where the annul i tended to be very i n d i s t i n c t e spec ia l ly ear ly i n l i f e . This l a t t e r phenomenon may be r e l a t ed to the very rapid ear ly growth of these f i s h . Any f i s h scale i n which the pos i t ion of the annul i was s t i l l questionable after three readings was discarded. Nevertheless without f i s h of known age for comparison, aging of f i s h by the scale method i s at best only ten ta t ive . False annul i due to spawning s t ress or other growth checks may be ind is t inguishable from r e a l ones. The calculated lengths at various ages are given for the four lakes i n Tables 16 to 19. Figures 21 to 24 present the average length at d i f ferent ages for the males and females of each lake . In each populat ion, male f i s h grow at about the same 48 ra te as females for the f i r s t two years of l i f e . Af ter t h i s , there i s an increasing d i spa r i t y i n the growth of the two sexes. Presumably t h i s i s re la ted to the onset of sexual maturity which d i f f e r e n t i a l l y affects the sexes. The difference i n growth i s probably even more pronounced than the figures indica te due to Table 16. Calculated t o t a l length at end of each year of l i f e of each age group and average growth for the combined age groups i n Cluculz Lake AGE GROUP NUMBER OF FISH LENGTH AT END OF YEAR 1 2 3 4 5 6 I 2 M 6.4 1 F 5.3 I I 2 M 5.5 9.6 3 F 5.5 9.1 I I I 20 M 5.0 8.6 10.7 56 F 5.3 8.9 11.2 — — — IV 10 M 5.1 7.6 10.0 11.2 •at —• —• .— 48 F 5.0 8.1 10.6 12.1 — V 5 M 4.7 8.0 9.9 11.0 11.8 6 F 5.2 8.4 10.9 12.7 13.6 VI 0 M 2 F 5.3 8.4 10.8 12.7 14.0 15.2 Grand average ca lcula ted length: M 5.1 8.4 10.4 11.1 11.8 _ _ F 5.2 8.6 10.9 12.2 13.7 15.2 Increment of average: M 5.1 3.3 2.0 0.7 0.7 F 5. 2 . 3.4 2.3 . 1.3 1.5 1.5 49 Table 17. Calculated t o t a l length at end of each year of l i f e of each age group and average growth for the combined age groups i n Tacheeda Lake AGE GROUP NUMBER OF FISH LENGTH AT END OF YEAR I 2 3 M F 5.8 5.8 I I 7 15 M F 5.7 6.1 8.o 8.9 I I I 3 45 M F 6.4 5.8 8.6 8.5 10.0 10.5 IV 0 31 M F 5.8 8.5 10.4 11.4 V 0 7 M F 5.7 7.9 10.2 11.5 12.4 — VI 0 1 M F 6.2 8.4 10.8 11.1 12.1 13.4 Grand average ca lcu la ted length: M 5.9 8.2 10.0 F 5.8 8.5 10.5 11.4 12.3 13.4 Increment of average: M 5.9 2.3 1.8 F 5.8 2.7 2.0 0.9 0.9 1.1 the se lec t ive effect of g i l l net sampling. In Tacheeda Lake, the extreme case, only twelve male f i s h were taken during the en t i re summer. There i s no reason to suppose that the unequal sex r a t i o i n the sample represents a r e a l s i t ua t ion i n the lake . Observations 50 Table 18. Calculated t o t a l length at end of each year of l i f e of each age group and average growth for the combined age groups i n MacLure Lake A G E N U M B E R L E N G T H AT END OF YEAR GROUP OF FISH 1 2 3 4 5 6 7 8 9 I OO M F I I 30 15 M F 5.3 5.4 8.7 8.7 I I I 4 M F 4.9 5.5 9.5 9.0 13.3 14.1 IV 14 9 M F 5.2 5.8 8.9 8.8 14.3 13.8 18.8 19.1 V 1 10 M F 4.7 5.5 8.7 8.9 13.0 15.2 15.6 19.9 17.4 22.8 VI 4 9 M F 4.9 5.0 7.8 8.4 13.4 13.5 17.5 18.1 19.8 20.6 21,5 23.2 VII 0 3 M F 6.1 8.5 15.0 20.4 22.4 23.9 25.0 — V I I I 0 0 M F IX 0 1 M F 6.8 10.5 15.6 18.3 21.5 22.5 23.6 25.0 26 Grand average ca lcu la ted length: M 5.2 8.8 13.9 18.4 19.3 21.5 -F 5.5 8.8 14.3 19.2 21.8 23.3 24.6 25.0 26.2 Increment of average: M 5.2 3.6 5.1 4.5 0.9 2.2 F 5.5 3.3 5.5 4.9 2.6 1.5 1.3 0.4 1.2 51 Table 19. Calculated t o t a l length at end of each year of l i f e of each age group and average growth for the combined age groups i n McLeese Lake AGE GROUP NUMBER OF FISH ' LENGTH AT END OF YEAR 1 2 3 4 5 I 0 M 0 F I I 3 M 6.5 9.5 —*«• 4 F 7.1 9.5 — — — I I I 11 M 7.3 11.2 14.6 36 F 7.0 10.9 14.8 — --IV 1 M 6.6 9.7 13.7 16.7 1 F 6.4 9.8 15.2 17.8 V 0 M 4 F 6.7 9.5 13.1 16.8 18.5 Grand average ca lcu la ted length: M 7.1 10.8 14.5 16.7 F 7.0 10.6 14.6 17.0 18.5 Increment of average: M 7.1 3.7 3.7 2.2 •— mm F 7.0 3.6 4.0 . 2.4 1.5 i n MacLure Lake indica te that the sexes school together so that i t i s u n l i k e l y that the disporportionate number of females i s the r e su l t of sampling i n areas where females are more l i k e l y to be found. Probably, most of the males of any one year class never reach a su f f i c i en t s i ze to become l i a b l e to capture by a one-inch g i l l net because of t he i r lower growth rate and greater mor ta l i ty SCALE MEASUREMENT (mm.) X 43.8 Figure 20. Relat ionship of scale diameter to fork ' length i n Lake Superior pygmy wh i t e f i sh Figure 21. 2 3 4 5 6 7 Y E A R O F L I F E Calculated length at end of each year of growth for Cluculz Lake pygmy wh i t e f i sh ( s o l i d l i n e -females; broken l i n e - males) Figure 22. 2 3 A 5 6 7 Y E A R O F L I F E Calculated length at .end of each year of growth for fEacheeda Lake pygmy whi te f i sh ( s o l i d l i n e -females; broken l i n e - males) MACLURE LK. YEAR OF LIFE Figure 23. Calculated length at end of each year of growth for MacLure Lake pygmy whi t e f i sh ( s o l i d l i n e - females; broken l i n e - males) 1 2 3 4 5 6 7 Y E A R OF LIFE Figure 24. Calculated length.at end of each year of growth for McLeese Lake pygmy whi t e f i sh 55 at young ages. S i g n i f i c a n t l y , most of the males were taken during September at a time when they would be approaching t he i r maximum seasonal growth and so coming to a s i ze at which one-inch g i l l nets would be more e f f ec t i ve . This was a lso the only time at which a h a l f - i n c h net was used. Thus the one-inch net, the p r i n c i p l e means of capture, crops only the faster growing or longer l i v e d males and therefore presents a biased pic ture of male growth ra tes . In Tacheeda, which has the slowest growing pygmy whi te f i sh i n the four l akes , the female growth rates may be s i m i l a r l y biased as might the ca lcu la ted growth rates for Cluculz Lake pygmys. By contras t , the f i s h i n McLeese and MacLure Lakes were probably inadequately sampled by the ava i lab le nets . Because of the poor representation of males i n some samples, comparison of growth i n the four populations has been r e s t r i c t e d to data for female f i s h . Table 20 presents data r e l a t ed to the growth i n length of f i s h from four lakes . L t and L t + ^ are, r e spec t ive ly , the average length of f i s h at the beginning and end of each year of growth. The increment i s the average increase i n length during any year, i n other words, L t + - |_ - L t . The instantaneous annual growth rate ( i ) i s defined as l o g 1 Q L t + 1 ( i n cms) - l o g 1 Q L t ( i n cms) The term, mean s i z e , as used here i s the mean s ize of the population at the midpoint of the growth period i f the animals are growing loga r i t hmica l l y . I t was calcula ted as Table 20. Mean fork length i n centimeters and instantaneous annual growth rates of pygmy whi te f i sh i n four B r i t i s h Columbia lakes I I I I I IV VI MacLure: Lt L t+1 Increment Mean Size 5.4 8.7 6.85 .20713 8.7 14.3 11.15 .21582 14.3 19.2 16.60 .12796 19.2 21.8 20.45 .05516 21.8 23.3 22.52 .02890 23.2 24.6 23.94 .02358 McLeese: Lt L t+1 Mean Size C lucu lz : Lt Lt+1 Mean Size 7.0 10.6 8.61 5.2 8.6 6.69 10.6 14.6 12.44 14.6 17.0 15.75 8.6 10.9 9.68 10.9 12.2 11.53 17.0 18.5 17.73 .18021 .13904 .06610 .03672 12.2 13.7 12.93 13.7 15.2 14.43 .21850 .10293 .04893 .0 5036 .04512 Tacheeda: L t L t+ I Mean Size 5.8 8.5 7.02 8.5 10.5 9.45 10.5 11.4 10.9 11.4 12.3 11.84 12.3 13.4 12.84 .16599 .09177 .03571 .03301 .03719 0 5 10 15 20 25 MEAN SIZE (FORK LENGTH) IN CENTIMETERS Figure 25'.. Plot to f- instantarieousrgrowth rate- aga-ins specified:.;size tf-or.-pygmy wh i t e f i s h i n four B r i t i s h Columbia Lakes 58 l o 8 1 0 L t + 1 + log L t a n t i l o g ( ) Lark in et a l . (1957), comparing the growth of d i f ferent populations of rainbow t rou t , state that " . . . i t i s desirable to dispense wi th age as a c r i t e r i o n of growth rate and to r e s t r i c t comparisons to growth rates of f i s h of the same s i z e , i . e . p lo t instantaneous growth rate against spec i f ied s i z e . " This has been done i n Figure 25. Most f ishes a t t a i n t he i r highest rate of growth during t h e i r f i r s t year of l i f e and thereafter the ra te of growth undergoes a rap id dec l ine . The graph shows that the expected decl ine takes place i n a l l four lakes . In Tacheeda Lake, which has the slowest growth rates for f i s h of comparable s i z e , the decl ine i s very rapid at f i r s t , but i t seems to be s t a b i l i z e d at about .035 for lengths above 11 cm. Samples of older f i s h are smal l , however, and may not be representat ive. Cluculz Lake f i s h are growing at a very high rate ear ly i n year I , but the rate of growth decl ines as r ap id ly as that of Tacheeda f i s h . The growth of larger f i s h i s a l so s i m i l a r i n kind to that of the Tacheeda populat ion. F i s h above 11.5 cm i n length appear to grow at a s table rate of .045 to .050. McLeese Lake f i s h show a decreasing rate of growth wi th increas ing s i z e , but the decl ine i s much less precipi tous than that i n Tacheeda or Cluculz Lake. As a consequence, moderately h igh growth rates are maintained over a wide range of s i z e s . Figure 26. Calculated length at end of each year of growth for female pygmy whi tef i sh i n four B r i t i s h Columbia lakes YEAR OF L IFE 60 The MacLure Lake population i s exceptional i n that during t he i r second year the instantaneous growth rate i s increas ing and th i s accelera t ion continues u n t i l the f i s h have reached a length of over 11 cm, when the inev i t ab le decl ine sets i n . The rate of decl ine i s moderate l i k e that of McLeese Lake pygrays. In Salmo ga i rdne r i , such i r r e g u l a r i t i e s i n the decl ine of growth rate wi th age have been a t t r ibu ted to changes i n niche which are a function of s i z e , s p e c i f i c a l l y , a change from plankton-feeding to piscivorous habits (Larkin et a l . , 1957). Conceivably, the exceptional increase i n the growth rate of MacLure Lake pygmy whi te f i sh r e su l t s from the attainment of some s i ze threshold which makes ava i lab le to them some h i ther to unavailable environmental resource. I t i s not known what t h i s might be. Figure 26 compares the lengths of female f i s h i n the four populations at various ages. At the end of the f i r s t year of growth, McLeese Lake f i s h have an average length which i s 1.0 to 1.8 cm greater than that of same-age f i s h i n the other three lakes . Instantaneous growth rates for year 0 have not been computed because the i n i t i a l s i z e of the f i s h i s unknown but the large s i ze of McLeese Lake f i s h at the formation of the f i r s t annulus i s undoubtedly the r e su l t of a higher growth ra te . The s i ze difference i s even greater at the end of year I , but only because of the larger i n i t i a l s i z e of McLeese f i s h . The growth rate i s ac tua l ly higher i n both Cluculz and MacLure Lakes. During t h e i r t h i r d summer the growth rate of the Cluculz Lake population undergoes the precipi tous decl ine already described, but that of MacLure f i s h ac tua l ly increases so that at the 61 formation of the t h i r d annulus they are only s l i g h t l y smaller than those from McLeese. In subsequent years, the MacLure population maintains i t s growth advantage and the f i s h are larger than McLeese pygmy whi te f i sh at every age. S i m i l a r l y , although Tacheeda Lake whi te f i sh are larger than e i ther the MacLure or Cluculz at the end of t h e i r f i r s t years, t h e i r growth rates decl ine more d r a s t i c a l l y than any, and i n the fo l lowing years they are always the smallest of the four. Age at Matur i ty Table 21 presents data r e l a t i n g to age at maturity for f i s h from the four study lakes . The determinations of state of maturity were made on f i s h taken four to eight months p r i o r to spawning, so that the data, e spec ia l ly for male f i s h , may be somewhat i n e r ro r . In most cases the f i s h are mature by the end of t h e i r t h i r d summer (age group I I ) . The exceptions are MacLure Lake where the f i s h of both sexes are not 100 per cent mature u n t i l age group IV and Tacheeda Lake where males are not a l l mature u n t i l age I I I . In Lake Superior (Eschmeyer and B a i l e y , 1954) a l l age group I I males were mature but females, l i k e MacLure Lake pygmy whi t e f i sh , matured more s lowly . In age group I I , only twenty per cent were mature and not u n t i l age IV were 100 per cent mature. Weisel and D i l l o n (1954) found numerous age I f i s h spawning i n B u l l Lake, Montana. These f i s h have an extianely rap id growth during t h e i r f i r s t two years of l i f e and the ear ly age of maturation may r e f l e c t 62 t h i s . In most l o c a l i t i e s pygmy whi te f i sh spawn sometime during November or December (Eschmeyer and B a i l e y , 1954) although Kendal l (1921) d id f i n d an Alaskan population spawning as ear ly as August. Table 21. Age at maturity of pygmy whi te f i sh i n four B r i t i s h Columbia lakes AGE GROUP NO. MALES % MATURE NO. FEMALES % MATURE MacLure I I I I I I IV 0 30 4 14 0 20 50 100 0 15 8 9 0 0 75 100 McLeese I I I I I I IV 0 3 11 1 0 100 100 100 0 4 35 1 0 100 100 100 Cluculz I I I I I I IV 2 2 21 8 0 100 100 100 1 3 56 46 0 100 100 96 Tacheeda I I I I I I IV 2 6 3 0 0 66 100 0 3 17 46 31 0 100 100 100 63 Indicat ions are that the four populations under study spawn, l i k e the majori ty , i n November or December. An except ional female, f i ve years of age and 12.3 cm i n length, co l l ec t ed i n Cluculz Lake on July 15, 1962 appeared to be r ipe and released eggs f ree ly when squeezed. No other f i s h i n s i m i l a r condi t ion were co l l ec ted even as la te as September 20, 1962. At the moment, i t seems best to regard t h i s f i s h as p h y s i o l o g i c a l l y a t y p i c a l . Both male and female pygmy whi te f i sh have nup t i a l tubercles at spawning time (Weisel & D i l l o n , 1954). These are most pronounced i n male f i s h . Several male f i s h co l l ec t ed during May i n Cluculz Lake s t i l l possessed unresorbed tubercules, but these were not apparent l a t e r i n the summer. New tubercles had not yet formed by mid-September. Length-Weight Relat ionship Figure 27 presents the length-weight r e l a t ionsh ip of preserved pygmy whi t e f i sh from MacLure Lake. The points represent a sample selected to provide a f a i r l y even d i s t r i b u t i o n of s i z e s . The l i n e has been f i t t e d by eye. Data for f i s h from the other three lakes appear to f a l l very nearly on the same l i n e . 64 Rela t ive growth Marr (1955) pointed out that the use of body dimensions expressed as per cent or per m i l l e of standard length could lead to confusing and doubtful conclusions. He recommended instead the wider use of regression analys is of the o r i g i n a l data as a t o o l i n the in te rpre ta t ion of a r e l a t i v e growth. In the present study, a ser ies of twelve measurements was made on f i s h from four lakes ( f i f t y f i s h each from Tacheeda and McLeese, and f i f ty -one f i s h each from Cluculz and MacLure). Per m i l l e r a t i o s of body parts to standard length were used only to determine whether there was a s i g n i f i c a n t difference i n the length of f in s between males and females. Eschmeyer and Bai ley (1954) report that Lake Superior males have larger f ins than females, but a ser ies of t - t e s t s f a i l e d to show any s ign i f i can t sexual dimorphism i n the four B r i t i s h Columbia populat ions. Consequently, the data for the two sexes have been combined. The data were converted to natural logs and a l i nea r regression of s i ze of body part against standard length was c a r r i e d out. The resu l t s then subjected to an analysis of co-variance. These are summarized i n Table 22. With the exception of head length, i n t e r o r b i t a l width , and a length of o r b i t , there i s no s i g n i f i c a n t difference i n the slope of r e l a t i v e growth l ines for the four lakes . The adjusted means are, however, s i g n i f i c a n t l y d i f ferent i n every case.(The tabled F value i s 2.65 at the .05 l e v e l , and 3.88 at the .01 l e v e l of s ign i f i cance . ) 66 The meaning of these d i f f e r e n c e s i n r e l a t i v e growth i s bes t a p p r e c i a t e d from a study of the graphs ( F i g s . 28 t o 39) which r e l a t e the common l o g a r i t h m of v a r i o u s body p a r t s to the common l o g a r i t h m of s tandard l e n g t h . In most cases a d i s t i n c t i o n can be made between the r e l a t i v e growth of the dwarf C l u c u l z and Tacheeda f i s h and t h a t of the l a r g e r f i s h from MacLure and McLeese. The dwarf forms have l a r g e r eyes , l a r g e r heads, longer m a x i l l a r i e s , s h a l l o w e r b o d i e s , and a narrower i n t e r o r b i t a l w i d t h . In a d d i t i o n , they have p r o p o r t i o n a t e l y longer p a i r e d and median f i n s . The a n a l f i n , though longer i n the dwarf forms, has a narrower base than t h a t of the l a r g e r f i s h . The w i d t h of the a n a l base does not appear t o be r e l a t e d t o the number of a n a l r a y s . The l e n g t h of the d o r s a l base may, however, be i n f l u e n c e d i n t h i s way. The C l u c u l z and McLeese Lake popu la t ions which have the l a r g e s t number of f i n elements a l s o have the broadest f i n bases . The p r e d o r s a l l e n g t h of the four p o p u l a t i o n s of Tacheeda and C l u c u l z Lakes have, r e s p e c t i v e l y , the longest and s h o r t e s t p r e d o r s a l measurements. S i m i l a r r e l a t i o n s h i p s between r a t e of growth and r e l a t i v e s i z e of body p a r t s have been noted i n o ther w h i t e f i s h e s . Svardson (1950) i n a s e r i e s of t r a n s f e r experiments i n v o l v i n g two spec ies of w h i t e f i s h e s found that i n each case the s lower growing p o p u l a t i o n had l a r g e r heads, sha l lower b o d i e s , l a r g e r eyes and long m a x i l l a r i e s . K o e l z (1929) showed tha t s low growing Coregonus c lupea formis r a i s e d i n the New York Aquarium had l a r g e r heads , eyes , snouts and pared f i n s than the f a s t e r growing parent s t o c k i n Lake E r i e . Table 22. Data r e l a t i n g measurements of various body parts to standard length f or four B r i t i s h Columbia lakes LAKE BD PDL LDB LBB HD HA LP LV HL IOW LP LUJ X l x 2 x 3 X4 X 5 X6 X7 X8 *9 X10 X l l X12 Tacheeda Lake Slope Intercept Correlation SE 1.148 -1.991 0.976 0.039 0.999 -0.808 0.991 0.020 0.958 -2.084 0.895 0.074 1.135 -2.610 0.926 0.071 0.990 -1.567 0.958 0.046 1.148 -2.048 0.955 0.055 1.103 -1.881 0.967 0.045 1.053 -1.883 0.975 0.037 1.041 -1.510 0.970 0.040 0.987 -2.744 0.937 0.057 0.933 -2.436 0.903 0.069 0.874 -2.422 0.917 0.059 Cluculz Lake Slope Intercept Correlation SE 1.091 -1.857 0.933 0.051 0.965 -0.752 0.980 0.024 0.927 -1.937 0.906 0.052 0.838 -1.830 0.817 0.072 0.047 -1.429 0.943 0.040 -1.090 -1.898 0.943 0.047 1.039 -1.702 0.935 0.048 0.945 -1.610 0.921 0.048 0.909 -1.263 0.954 0.035 0.915 -2.564 0.881 0.060 0.754 -2.007 0.899 0.045 0.722 -2.063 0.814 0.063 McLeese Lake Slope Intercept Correlation SE 1.102 -1.834 0.982 0.035 1.018 -0.852 0.994 0.019 1.028 -2.161 0.964 0.047 1.023 -2.255 0.960 0.940 0.937 -1.451 0.970 0.039 1.049 -1.881 0.973 0.041 1.036 -1.783 0.973 0.040 0.991 -1.787 0.969 0.041 0.996 -1.466 0.988 0.026 1.136 -2.996 0.968 0.048 0.795 -2.218 0.958 0.039 0.844 -2.392 0.934 0.053 MacLure Lake Slope Intercept Correlation SE 1.118 -1.872 0.991 0.049 1.012 -0.855 0.998 0.022 0.975 -2.062 0.986 0.054 1.028 -2.289 0.083 0.062 0.948 -1.513 0.993 0.035 1.069 -1.027 0.987 0.055 1.036 -1.831 0.993 0.040 0.981 -1.812 0.990 0.045 0.913 -1.278 0.996 0.026 1.060 0.722 -2.874-2.061 0.990 0.980 0.049 0.047 0.816 -2.332 0.980 0.053 Slope F Adj.Mean F. 0.321 12.710 1.179 20.506 0.567 22.016 1.899 79.610 1.660 1646.340 0.057 27.078 0.776 68.995. 1.144 6.479** 3.244* 5.488** 1.122 a 48.544 38.650 1956.890 54.985 1478.610 " -.65 at 5% 3.88 at 1% Figure 28 Relat ionship of predorsal length to standard length Figure 29 Relat ionship of head length to standard length Triangles Cluculz Crosses McLeese C i r c l e s MacLure Squares Tacheeda Figure 30) Relat ionship of body depth to standard length Figure 31 Relat ionship of i n t e r o r b i t a l width to standard length Triangles Cluculz Crosses McLeese C i r c l e s MacLure Squares Tacheeda ' ' ' ' ' I I J 6 7 8 9 10 15 20 30 STANDARD LENGTH(cm.) F i g u r e 32 R e l a t i o n s h i p of o r b i t l e n g t h t o s tandard l e n g t h F i g u r e 33 R e l a t i o n s h i p of l eng th of upper jaw t o s tandard l e n g t h T r i a n g l e s C l u c u l z Crosses McLeese C i r c l e s MacLure Squares Tacheeda Figure 34 Relat ionship of length of dorsal f i n base to standard length Figure 35 Relat ionship of length of anal f i n base to standard length Triangles Crosses C i r c l e s Squares Cluculz McLeese MacLure Tacheeda I I I I I I I J 6 7 8 9 10 15 20 30 STANDARD LENGTH (cm.) F i g u r e 36 R e l a t i o n s h i p of he ight of a n a l f i n t o s tandard l e n g t h F i g u r e 37 R e l a t i o n s h i p of he ight of d o r s a l f i n t o s tandard l e n g t h T r i a n g l e s C i r c l e s Crosses Squares C l u c u l z MacLure McLeese Tacheeda 601 HEIGHT ANAL FIN F i g . 36 7-6-5 -U -' • ' L_J I L - J 6 7 8 9 10 15 20 30 STANDARD LENGTH (cm.) F i g u r e 38 F i g u r e 39 R e l a t i o n s h i p of l e n g t h of p e c t o r a l f i n t o s tandard l e n g t h R e l a t i o n s h i p of l e n g t h of p e l v i c f i n t o s tandard l e n g t h T r i a n g l e s C l u c u l z Crosses McLeese C i r c l e s MacLure Squares Tacheeda LENGTH PECTORAL FIN Fig e38 7 -6 -5 -4 -' i i i i I I LI 6 7 8 9 10 15 20 30 STANDARD LENGTH (cm.) 74 Mart in (1949), by c o n t r o l l i n g the growth rates of rainbow trout through va r i a t i on i n temperature and d i e t , was able to produce differences i n body form. He demonstrated that the r e l a t i v e growth of body parts i n fishes was characterized by a ser ies of stanzas separated by sharp i n f l ec t i ons i n the r e l a t i v e growth constant. Generally speaking, there are four d i s t i n c t stanzas: at the eyed stage, at hatching, at o s s i f i c a t i o n , and at matur i ty . Mart in concluded that " . . . i n general there i s no causal connection between body form i n fishes and e i ther rate of development of subsequent growth ra te , although e i the r of these processes may indirectly affect con t ro l of body firm through t h e i r influence on s i ze at matur i ty ." In most cases the differences between populations of the same species are differences i n the intercept of the growth l ines rather than i n the slope of the l i n e s . Mart in was, however, able to pmduce slope differences i n the r e l a t i v e growth of the eyes and head by severely r e s t r i c t i n g the d ie t of experimental f i s h . In te res t ing ly , both these measurements show s ign i f i c an t differences i n slope i n the pygmy w h i t e f i s h . I t i s not known whether these differences might a lso be the r e su l t of def ic ien t d ie t i n the dwarf populations. I t i s very l i k e l y that the r e l a t i v e proportions of body parts i n the pygmy whi te f i sh are determined i n much the same way as that described by Mart in for the rainbow trout and other f i s h . Unfortunately, no small f i s h are ava i lab le from the populations under study so that there i s no d i r ec t evidence of growth i n f l e c t i o n s i n the pygmy w h i t e f i s h . Thus, although there are def in i t e differences i n the populations of the four lakes, the mechanics of determination a re not known. Depth D i s t r i b u t i o n Tables 23 and 24 summarize ne t t ing data for the summer of 1962. The tables include the t o t a l e f for t expended i n a p a r t i c u l a r depth stratum and the t o t a l catch of f i s h which resu l t ed . The uni t of e f f o r t , the net-hour was defined as a s i n g l e , f i f t y -foot long, e ight-foot deep monofilament nylon net f i s h i n g for a per iod of one hour. Data from twenty-five-foot deep nets were not used because these were not cons is tent ly employed. The data for the whole summer are summarized as catch per un i t of e f for t ( f i s h per net-hour) for each depth stratum and the resu l t s graphed i n Figure 40. For Tacheeda and Cluculz Lakes, data for two other whi tef i shes , Coregonus clupeaformis and Prosopium w i l l i a m s o n i , have been included. The data show two d i s t i n c t patterns of depth d i s t r i b u t i o n . In both McLeese and MacLure lakes , pygmy whi te f i sh extend from a depth of about f i f t een feet downward to depths of seventy and f i f t y feet r e spec t ive ly . Extensive net t ing i n deeper waters f a i l e d to produce a s ingle pygmy whi t e f i sh . In the other two lakes , Cluculz and Tacheeda, the upper l i m i t of d i s t r i b u t i o n i s about t h i r t y - f i v e feet , and the f i s h are numerous as far as the l i m i t of ne t t ing , 120 feet i n Cluculz and 100 feet i n Tacheeda l ake . In MacLure and McLeese Lakes the upper l i m i t of d i s t r i b u t i o n may coincide wi th the depth of the warmer e p i l i m n i a l water. In the other two lakes the depth d i s t r i b u t i o n during the summer i s considerably below that of the thermocline and may be Table 23. Depth d i s t r i b u t i o n and c a t c h of pygmy w h i t e f i s h i n MacLure and McLeese Lakes d u r i n g summer, 1962 DATE DEPTH STRATUM MacLure Lake : E i g h t - f o o t bottom sets 0-10 net no . hr s f i s h 10-net hr s 20 no. f i s h 20-net h r s 30 no. f i s h 30-net hrs 40 no. f i s h 40-net h r s 50 no . f i s h 50-net h r s 60 no . f i s h 60-70 net no . h r s f i s h June 2-6 48 J u l y 6-10 7% J u l y 31 0 Sept 20 0 0 0 0 0 36 17% 0 0 2 5 0 0 58 81% 7% 0 9 172 8 0 175 76 7% 96 26 28 8 46 40% 72 7% 0 8 0 8 0 34% 0 0 0 0 0 0 0 0 0 62 0 0 0 0 0 T o t a l 55% 0 53% 7 147 138 354 108 120 16 34% 0 62 0 C a t c h / u n i t e f f o r t 0.000 0.131 0.929 0.305 0.133 0.000 0.000 McLeese Lake : E i g h t - f o o t bottom sets 0-20 20- 40 40- 60 60- 80 80- 100 100 -120 June 13-16 29 J u l y 23 12 Sept 0 0 0 0 108 12 7 Ik 9 0 0 0 12 39% 0 8 0 0 51% 45 0 0 0 0 10% 16% 0 0 0 T o t a l 41 0 191% 9 51% 8 96% 0 27 0 C a t c h / u n i t e f f o r t .000 .047 .156 .000 .000 ON Table 24. Depth d i s t r i b u t i o n and catch of pygmy whi te f i sh i n Cluculz and Tacheeda Lakes during summer, 1962 (P - pygmy; M - mountain; L - lake whi tef i sh) DATE DEPTH STRATUM Cluculz Lake: Eight-foot bottom sets 0-20 20-40 40-60 60-80 80-100 100-120 net catch net catch net catch net catch net catch net catch hrs P M L hrs P M L hrs P . M: L hrs P M L hrs P M L hrs P M L 5/21-31 0 0 0 0 212 19 0 0 22 0 0 6 0 0 0 o; 0 0 0 0 6/10-24 159 0 27 20 93.5 3 12 6 35 19 0 0 8 10 0 0" 0 0 0 0 — —t 7/13-30 308 0 50 3 217.6 3 32 7 109.8 35 0 0 31 44 0 0 7 1 0 0 28 23 -0 0 Tota l 467 0 77 23 527 25 44 13 167 54 0 0 39 54 0 0 7 1 0 0 28 23 0 0 Catch per un i t e f fo r t : .000 P .047 P .323 P 1.385 P .143 P .821 P .164 M .083 M .000 M .000 M .000 M .000 M .049 L .025 L .000 L .000 L .000 L .000 L Tacheeda Lake: Eight-foot bottom sets 5/18 22 0 0 4 22 0 0 2 22 4 0 0 0 0 0 0 0 0 0 0 6/20-1 120.4 0 5 6 73.9 1% 2 8 42.8 9% 0 0 37.5 8 1 0 0 0 0 0 — — 7/20-2 61.2 0 43 17 100.5 5 12 18 74.4 29 0 5 17 2 0 0 0 0 0 0 mm mm 9/16 0 0 0 0 10 0 0 0 20 2 0 0 15 7 0 0 20 20 0 0 20 0 0 0 Tota l 203.6 0 48 27 206.4 6% 14 28 159.2 34J>0 5 69.5 17 1 0 20 20 0 0 20 0 0 0 Catch per un i t e f for t : .000 P .031 P .217 P .245 P 1.000 P 0.000 P .236 M .068 M .000 M .014 M 0.000 M 0.000 M .137 L .136 L .031 L .000 L 0.000 L 0.000 L 78 Figure 40 Depth d i s t r i b u t i o n s of whitefish i n four B r i t i s h Columbia Lakes during Summer, 1962 l a r g e l y the r e s u l t of c o m p e t i t i v e e x c l u s i o n by the other two w h i t e f i s h . Both of these Coregonus c lupea formis and Prosopium  w i l l j a m s o n i are most abundant inshore and t h e i r lower l i m i t o f d i s t r i b u t i o n almost e x a c t l y c o i n c i d e s w i t h the upper l i m i t of pygmy d i s t r i b u t i o n . The lumping of data p a r t l y obscures t h i s . A l t h o u g h a l l three w h i t e f i s h e s o f t en occurred i n the same depth s t r a t u m , r a r e l y was another spec ies of w h i t e f i s h found below a pygmy w h i t e f i s h i n a n e t . Except ions were a mountain w h i t e f i s h taken June 20-21 i n the 60 - 80 foot s t ra tum i n Tacheeda Lake and four lake w h i t e f i s h taken i n f i f t y fee t of water on J u l y 21 i n Tacheeda. The s h a l l o w lower l i m i t o f pygmy d i s t r i b u t i o n i n MacLure and.McLeese Lakes i s probably due t o low oxygen t ens ions the bottom w a t e r s . Both lakes have h i g h T o t a l D i s s o l v e d S o l i d s va lue s and are q u i t e p r o d u c t i v e . On J u l y 31 , 1962, the waters o f MacLure Lake from t h i r t y - t h r e e f ee t to the bottom conta ined o n l y 2 .4 mg/1 of Oxygen. No f i g u r e s a re a v a i l a b l e f o r McLeese l a k e , but a s i m i l a r s i t u a t i o n may have p r e v a i l e d . Both C l u c u l z and Tacheeda are deeper, more o l i g o t r o p h i c l a k e s . On J u l y 30 , 1962 the water a t 105 fee t i n C l u c u l z Lake s t i l l conta ined 4 .4 mg/1 of Oxygen. There i s no evidence of any d i u r n a l v e r t i c a l or h o r i z o n t a l ( i n s h o r e - o f f s h o r e ) movements i n the pygmy w h i t e f i s h . There i s some ev idence , however, of an o f f shore movement i n t o somewhat deeper water d u r i n g l a t e s p r i n g . In s h a l l o w O u t l e t Bay, C l u c u l z Lake , numerous pygmys were taken a t depths of 25 t o 30 f e e t d u r i n g May. Nets set i n the same area l a t e r i n the summer 80: :v. f a i l e d to take any pygmy wh i t e f i sh . Residents report s i m i l a r movements of lake whi te f i sh and lake t rou t . Mountain whi te f i sh are abundant i n the bay at a l l times. There i s no adequate evidence of th i s sort for the other lakes . At the depths where i t occurs, the pygmy whi te f i sh i s by far the most numerous f i s h . In Cluculz and Tacheeda only the lake trout was commonly taken at such depths. In MacLure Lake there was a zone of overlap between f i f t een and twenty feet where the redside shiner (Richardsonius ba l tea tus) , peamouth chub (Mylocheilus caurinum) and squawfish (Ptychocheilus oregonensis) were a l l common, but below th i s depth,nets contained pygmy whi te f i sh almost e x c l u s i v e l y . Food habits Only prel iminary studies have been ca r r i ed out on the food of pygmy whi te f i sh i n the four lakes . The resu l t s are given i n Table 25. In each case the three most important foods are cladocerans, chironomid larvae, and Chaeoborus. The r e l a t i v e importance var ies considerably, however, even wi th in the same lake . In Tacheeda Lake, for instance, cladocerans made up 907o of the stomach contents on Ju ly 23, but on September 21 they represented only 1% of the d i e t . By contrast , the proportion of chironomid larvae had r i s e n from 2% to 85%. In MacLeese Lake, a s i m i l a r r e l a t ionsh ip holds for Chaeoborus and chironomid larvae . In MacLure and Cluculz Lakes, the main constituent of the die t i s Cladocera and chironomidae, r e spec t ive ly , on each of three separate 81 dates. In Lake Superior, Amphipods (Pontoporeia) and ostracods made up 75% of the t o t a l stomach contents of pygmy whi te f i sh (Eschmeyer and B a i l e y , 1954). In Brooks Lake, Alaska , pygmy whi te f i sh had a die t of plankters and few of the smallest insects (mainly chironomid la rvae) . Cladocterans , copepods, and ostracods were a l l recorded as present. No amphipods were found although these were present i n the stomachs of other species i n the lake (Hartman, 1957 and 1958). The pygmy whi te f i sh i s probably an opportunis t ic feeder, tak ing whatever foods are r ead i ly ava i lab le at any given time, and the va r i a t i on i n foods eaten i n various lakes i s not unexpected. What i s consistent i n the die t from lake to lake i s the s i ze of the food organisms. Even the largest MacLure Lake whi te f i sh are r e s t r i c t e d to r e l a t i v e l y t i n y plankters and bottom organisms. By contras t , both Coregonus clupeaformis and Prosopium wi l l i amson i can, and do, feed on much larger organisms, c h i e f l y molluscs and the larger aquatic insects (McHugh, 1939 and 1940; and Godfrey, 1955). P. w i l l i a m s o n i , i n p a r t i c u l a r , r a r e ly takes plankton or other small organisms as an adul t . Hartman (1958) has shown that s ize of food organisms can be re la ted to the s i ze of the mouth i n rainbow t rou t . Observations indica te that , contrary to expectation, P; w i l l i amson i has a very t i n y mouth. The pygmy wh i t e f i sh , wi th an intermediate mouth s i z e , has a longer m a x i l l a r y , greater width between the m a x i l l a r i e s and a larger gape. Of the three, C. clupeaformis has Table 25. Stomach contents of pygmy whi te f i sh from four B r i t i s h Columbia lakes expressed as estimated percentage of t o t a l volume. A l l f i s h taken i n 1962.. MACLURE LAKE MCLEESE LAKE CLUCULZ LAKE TACHEEDA LAKE Date: 6/4,5 8/1 9/20 6/18 7/24 5/23 6/23 9/18 7/23 9/21 Stomachs examined: 5 10 10 5 5 5 5 5 10 5 Mollusea Sphaeriidae — -- — -- t r -- — Crustacea Ostracoda Cladocera Copepoda Amphipoda 60 91 t r 73 5 t r 10 t r — t r t r t r 90 2 l " t r Insecta Chironomidae Chaeoborus 30 7 2 10 8 82 75 10 60 10 70 25 10 2 85 3 Uniden t i f i ab le 10 2 15 5 5 20 30 65 6 10 GO ro 83 the largest mouth i n every respect . The choice of food i s not, then, s t r i c t l y a function of mouth s i z e . Mouth shape, may, however, be important. Both C. clupeaformis and e spec ia l ly P. w i l l i amson i have more pointed snouts than P. co i l t e r i w i th i t s b lunt , broad nose. Pointedness may be advantageous i n probing under rocks , s t i c k s , e tc . for large insects and s n a i l s . The wide mouth of the pygmy may be more e f f i c i e n t i n s t r a i n i n g mud and water for small bottom animals and plankton. Plankton feeding species generally have more g i l l rakers than bottom feeders. In th i s case the pygmy whi te f i sh (12-20) has not more, but fewer, rakers than e i ther the lake whi t e f i sh (23-33) or the mountain whi te f i sh (20-26). (Figures for the l a s t two species are from C a r l , Clemens, and Lindsey, 1959). 84 DISCUSSION The data give ample evidence of s t r i k i n g differences i n the growth form of d i f ferent populations of pygmy wh i t e f i sh . I t i s very d i f f i c u l t , however, to assign s p e c i f i c causes for these dif ferences . La rk in (1956) has commented on the impermanence of freshwater environments which, i n terms of geologica l time periods, are very s h o r t - l i v e d . This i s e spec ia l ly true of the temperate regions of the wor ld . As a response to the ephemeral nature of t h e i r environment, f ishes occupying fresh waters have developed a remarkable p l a s t i c i t y i n terms of the habitat and, more p a r t i c u l a r l y , the niche which they can occupy. The v a r i a b i l i t y i n m e r i s t i c s , morphometry and growth ra te , excempEfied i n the pygmy wh i t e f i sh , i s a r e f l e c t i o n of t h i s a b i l i t y to adapt to r a p i d l y changing condi t ions . The differences may be la rge ly the r e su l t of environmental modif icat ion but the gene complement which permits such a wide range of phenotypic expression must i t s e l f be the r e su l t of r igorous s e l ec t i on . The niche that a species occupies i n a p a r t i c u l a r l o c a l i t y i s determined by a complex of factors both phys ica l and b i o t i c . The i n t e r - r e l a t i o n s of these are not w e l l understood. In f i s h the d i s t r i b u t i o n and abundance of food organisms and the presence of other competing species are most often mentioned as 85 f a c t o r s r e s u l t i n g i n n i c h e d i v e r s i t y w i t h i n a s i n g l e s p e c i e s . The mountain w h i t e f i s h p rov ide s an example of the d i r e c t e f f e c t of food abundance on cho ice of n i c h e . In most areas t h i s w h i t e f i s h i s a s h a l l o w wate r , bottom feeder c o n c e n t r a t i n g i t s f e e d i n g on immature i n s e c t s . In M o r r i s o n Lake , BC, however, the v e r y steep s ide s s e v e r e l y l i m i t the s h a l l o w water areas g e n e r a l l y i n h a b i t e d by such i n s e c t s and the mountain w h i t e f i s h has become p r i m a r i l y a p l a n k t o n feeder (Godfrey, 1955). A s i m i l a r phenomenon seems t o have occurred i n Okanagan Lake (McHugh, 1939). The e f f e c t s of c o m p e t i t i o n w i t h o ther spec ies are much more d i f f i c u l t t o a s ses s . Mayr (1948) has s t a t e d t h a t "So f a r t h e r e i s o n l y scanty d i r e c t proof f o r the assumption t h a t p o p u l a t i o n s are kept i n check by c o m p e t i t i o n f o r space and f o o d . " Andrewartha and B i r c h (1954) concluded that the a v a i l a b l e evidence suggests the c o m p e t i t i o n i n n a t u r a l s i t u a t i o n s occurs on ly r a r e l y a t b e s t . Much of the d i f f i c u l t y a r i s e s because of our i n a b i l i t y t o c o n t r o l the n a t u r a l environment. A common technique i s to compare two p o p u l a t i o n s of a s p e c i e s ; one i n w h i c h the spec ies occurs a l o n e , and another i n which the species occurs together w i t h p o s s i b l e c o m p e t i t o r s . U n f o r t u n a t e l y , "Most of these demonstrat ions are hampered by the d i f f i c u l t i e s of r u l i n g out the e f f e c t s of changes i n the environment o ther than the changes i n f i s h fauna and the d i f f i c u l t i e s of g e t t i n g a good measure of the •adverse e f f e c t ' on a l l the competing f i s h p o p u l a t i o n s . " (L inds t rom and N i l s s o n , 1962). Thi s i s very d e f i n i t e l y a problem i n comparing the pygmy w h i t e f i s h popu la t ions of the four l akes under s tudy , l akes which are q u i t e d i s s i m i l a r l i m n o l o g i c a l l y . 86 Johannes and L a r k i n (1961) emphasise another d i f f i c u l t y . In most cases the s c i e n t i s t i s presented w i t h a " f a i t a c c o m p l i " . He i s , i n f a c t , s t u d y i n g the r e s u l t s r a t h e r than the process of c o m p e t i t i o n and may have l i t t l e i d e a of the changes tha t the advent of a competing spec ies have wrought i n the ecology of another . S i t u a t i o n s l i k e tha t at P a u l Lake , B r i t i s h Columbia , where t h e r e i s c o n s i d e r a b l e i n f o r m a t i o n a v a i l a b l e on the growth of the rainbow t r o u t both before and a f t e r the i n t r o d u c t i o n of the competing r e d s i d e s h i n e r are not common. In the present s t u d y , the f i s h fauna of the lakes has probably been s t a b l e f o r long per iods of t ime so tha t there i s no evidence of the c a u s a l sequence through which the present c o n d i t i o n s developed. F i n a l l y there i s the problem of s imply d e f i n i n g the term " c o m p e t i t i o n " . I t has been used i n many ways, even i n c l u d i n g p a r a s i t i s m and p r e d a t i o n . L a r k i n (1956) suggests that the term " c o m p e t i t i o n " be r e s t r i c t e d i n use t o " . . . t h e demand, t y p i c a l l y a t the same t i m e , of more than one organism f o r the same resources of the environment i n excess of immediate s u p p l y . " Such c o m p e t i t i o n i s g e n e r a l l y most severe i n c l o s e l y r e l a t e d s p e c i e s . S i g n i f i c a n t l y , the l a r g e r s i z e d MacLure and McLeese Lake p o p u l a t i o n s are the o n l y two i n B r i t i s h Columbia where the pygmy w h i t e f i s h does not c o - e x i s t w i t h another spec ies of the genus Prosopium. In every o ther l o c a l i t y , e i t h e r P. w i l l i a m s o n i or P . cy l indraceum i s present and the dwarfed form of P . c o u l t e r i i s the r u l e . N i l s s o n (1955) suggests s e v e r a l p o s s i b l e r e s u l t s of c o m p e t i t i o n . In the f i r s t ca se , severe c o m p e t i t i o n leads t o the 87 e l imina t ion of one of the species from the area. The sever i ty of competition may be due to a genetic make-up which Includes factors for reproductive i s o l a t i o n but not for eco log ica l compa t ib i l i t y . I t may a l so be the resu l t of factors which l i m i t the number of niches a v a i l a b l e , forc ing the two species together. Lindstrom and Ni l sson (1962) considered competition between whitefishes to be more severe i n a narrow, deep lake wi th few niches than i n a shallower one wi th a wide l i t t o r a l zone providing more var ied resources. Muira (MS) has shown that i n B r i t i s h Columbia's Fraser River drainage the number of species inhab i t ing lakes increases wi th the surface area. A s i m i l a r r e la t ionsh ip ex i s t s for the four lakes studied i n terms of both the t o t a l number of species and the number of whi te f i sh species. The two smaller lakes have only a s ingle whi te f i sh species whi le three species inhabi t the larger lakes . In MacLure Lake, at l eas t , the absence of the mountain whi te f i sh i s not due to i n a c c e s s i b i l i t y . The lake i s connected to the Bulkley R i v e r , where these f i s h occur, by a stream less than two miles long. There appears to be no ba r r i e r to movement along the length of the stream. In the case of McLeese Lake, invasion of mountain whi te f i sh from downstream i s d e f i n i t e l y cut of by an impassable f a l l s on Soda Creek where i t drains in to the Fraser R i v e r . In the second s i t ua t i on r e s u l t i n g from competit ion, the two species are able to co-exis t without severe competition by e i ther occupying d i f ferent types of habitat or by obtaining t h e i r food and other necessary resources i n di f ferent ways ( i . e . occupying d i f ferent n iches ) . Brian (1956) suggests that t h i s 88 eco log i ca l separation of species can come about i n two ways. I t may be based on s t r i c t l y d i f f e r e n t i a l habitat se lec t ion which i s presumably the r e su l t of genetic differences or i t may be the r e s u l t of effects that the species i n contact have upon one another. The former, Brian termed se lec t ive segregation, and the l a t t e r i n t e r ac t i ve segregation. In Cluculz and Tacheeda Lakes the adult pygmy whi te f i sh very d e f i n i t e l y occupies a d i f fe ren t niche than e i the r the lake or mountain wh i t e f i sh . I t i s a dwarfed f i s h feeding on plankton and small bottom fauna and inhabi t ing deep waters. The other two are normal i n s i z e , feed on large bottom fauna and inhabi t shallower waters. Are these differences i n niche the r e su l t of s e l ec t ive or i n t e rac t ive segregation? The answer to t h i s question i s not c l e a r , but some ins igh t may be gained by a comparison of the two lakes having sympatric whi te f i sh populations wi th McLeese and MacLure where the pygmy whi t e f i sh ex i s t s alone. Ni l s son (1955) found that i n competitive s i t ua t i ons , the trout (Salmo t ru t ta ) i s mainly a bottom feeder and tends to occupy shallow water. Char (Salvel inus alpinus) i n the same lakes feed p r imar i ly on plankton and occupy the open, deep waters. Alone, or when bottom insects are superabundant, the char i s much more evenly spread over the basin of the lake and moves i n to shallow water. Char feeding p r imar i l y on plankton grow much more slowly than those wi th access to bottom fauna. A s i m i l a r pattern i s apparent for the pygmy wh i t e f i sh . Alone, the pygmy whi te f i sh occupies shallower water and grows to considerably larger s izes than i t does when co -ex i s t i ng wi th other species of w h i t e f i s h . 89 There does n o t , however, appear t o be any s i g n i f i c a n t change i n food h a b i t s from lake t o l a k e . The o f t remarked r e l a t i o n between f i s h s i z e and food s i z e ( L i n d s t r o m , 1955) i s not shown. Dahl (1917 and 1926), c i t e d i n N i l s s o n (1955) , p o i n t e d out tha t s m a l l e r or l e s s a v a i l a b l e food ob jec t s r e q u i r e a g r e a t e r expendi ture of energy by the f i s h i n r e l a t i o n t o the q u a n t i t y of food o b t a i n e d , and thus r e s u l t i n a lower growth r a t e . In the case of the pygmy w h i t e f i s h the s i z e of the food p a r t i c l e s does not appear t o d i f f e r but t h e r e i s a very d i s t i n c t d i f f e r e n c e i n the growth r a t e s from lake t o l a k e . The reason f o r t h i s may l i e i n the v a r i a t i o n i n d e n s i t y of food of the a p p r o p r i a t e s i z e i n the volume of water i n h a b i t e d by the pygmy w h i t e f i s h i n the d i f f e r e n t l a k e s . In the f i r s t p l a c e , McLeese and MacLure Lakes , w i t h h i g h e r TDS and s h a l l o w e r w a t e r s , would be expected t o produce g rea te r q u a n t i t i e s of zooplankton and s m a l l bottom organisms than e i t h e r Tacheeda or C l u c u l z . Secondly , much of the pygmy w h i t e f i s h p o p u l a t i o n of Tacheeda and C l u c u l z i s conf ined t o c o n s i d e r a b l e depths where low temperatures and low l i g h t i n t e n s i t i e s must s e v e r e l y l i m i t the p r o d u c t i o n of food organisms and a t the same t ime reduce the e f f i c i e n c y of food c o n v e r s i o n . D i f f e r e n c e s i n average s i z e would undoubtedly e x i s t even i f the depth d i s t r i b u t i o n s of pygmy w h i t e f i s h i n the f o u r lakes were i d e n t i c a l but they might not be n e a r l y as g rea t . Pygmy w h i t e f i s h are o b v i o u s l y capable of i n h a b i t i n g s h a l l o w e r w a t e r . Why then are they found o n l y i n deep water i n Tacheeda or C l u c u l z ? The answer may l i e i n the f a c t tha t the young of both mountain and the l ake w h i t e f i s h e s have a d i e t e s s e n t i a l l y s i m i l a r to that of the pygmy whi te f i sh plankton and other small organisms. I t may be that the pygmy, unable to compete for food i n the inshore nursery areas of these species , has been forced in to deeper, less productive water. The pygmy whi t e f i sh might have reacted to competition and the supposedly decreased food supply by a d ra s t i c reduction i n numbers rather than by an equally d ras t i c reduction i n s i ze of i n d i v i d u a l s . Dwarfed races of otherwise normal species are often encountered i n competitive s i tua t ions . Evident ly dwarfing gives these species some advantage i n competition wi th larger ones. Lindstrbm and Ni lsson (1962) suggest that the shorter l i f e span and more r ap id population turnover of dwarf f i s h may r e su l t i n a greater u t i l i z a t i o n of the ava i lab le resources and thus afford them a greater measure of success i n competit ion. To answer the o r i g i n a l question, then, there does appear to be some i n d i c a t i o n of i n t e rac t ive segregation between the pygmy whi te f i sh and the two other whitefishes which resu l t s i n d i s t i n c t differences i n depth d i s t r i b u t i o n and growth ra te . The evidence i s hardly conclusive however, and u n t i l the f i s h are subjected to a greater measure of experimental c o n t r o l , no de f in i t e conclusions are poss ib le . 91 SUMMARY 1) An analys is of mer i s t i c va r i a t i on i n twelve populations of pygmy whi te f i sh inhabi t ing B r i t i s h Columbia and Alaska revealed a high degree of v a r i a b i l i t y both wi th in and between populat ions. 2) A l a t i t u d i n a l comparison of means of mer i s t i c characters for these and f ive add i t iona l populations revealed a tendency, i n counts of anal rays and vertebrae, toward an increase i n parts i n the more southerly populat ions. The same tendency may be present i n counts of pec tora l rays and p y l o r i c caeca. La t e r a l l i n e scale counts seem to vary randomly. The r e l a t i o n between g i l l raker counts and la t i tude appears to be V-shaped. 3) Age and growth was determined for four B r i t i s h Columbia lakes using the scale diameter measurement. Other scale dimensions were unusable because of i n f l e c t i o n s i n the scale-body r e l a t ionsh ip subsequent to the f i r s t annulus (an te ro- la te ra l r idge and anter ior radius) or because the annul i were unclear (scale length) . 92 4) As adul t s , MacLure pygmy whi te f i sh are la rges t , followed i n order by f i s h from McLeese, Cluculz and Tacheeda Lakes. Adult s i ze i s corre la ted wi th the rate of decline of the ins tant -aneous annual growth rate ( i ) . 5) In MacLure Lake pygmy whi te f i sh were not a l l mature u n t i l age IV. In the other three, most f i s h were mature at age I I . 6) Analys is of covariance reveals that the dwarf pygmys of Cluculz and Tacheeda Lakes have s i g n i f i c a n t l y larger eyes, larger heads, longer m a x i l l a r i e s , shallower bodies, narrower i n t e r o r b i t a l width , and longer paired and median f i n s . Predorsal length does not appear to vary i n any predictable manner. The width of the anal base appears to be re la ted to the number of anal rays . Length of the dorsa l base i s not re la ted to the number of f i n elements. 7) The dwarf f i s h of Cluculz and Tacheeda lakes inhabi t much deeper water than those of McLeese and MacLure Lakes. 8) Pygmy whi te f i sh appear to be r e s t r i c t e d to a d ie t of small bottom and planktonic organisms. There was no apparent difference between the d ie ts of f i s h from the four lakes. 9) There may be a r e l a t ionsh ip between the absence of other whi te f i sh species and the large s ize of pygmy whi te f i sh i n McLeese and MacLure Lakes. 94 BIBLIOGRAPHY Andrewartha , H . G . , and L . C. B i r c h . 1954. The d i s t r i b u t i o n and abundance of a n i m a l s . Chicago, 782 pp . Bar low, George W. 1961. Gobies of the genus G i l l i c h t h y s , w i t h comments on the sensory cana l s as a taxonomic t o o l . Copeia 4:423-437. B r i a n , M. V . 1956. Segregat ion of the spec ies of the ant genus Myrmica . J . Anim. E c o l . 25(2) :319-337. C a r l , G. C l i f f o r d , W. A . Clemens and C. C. L i n d s e y . 1959. The f re sh-water f i s h e s of B r i t i s h Columbia. BC P r o v . Museum Handbook No. 5 . D a h l , K. 1917. S t u d i e r og fors(6k over j6rret og |6rretvand. F i sker i inspekt$6rens i n n b e r e t n i n g om f e r k v a n d s f i s k e r i e n e . 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