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The effect of intertidal exposure on the survival and embryonic development of Pacific herring spawn 1971

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THE EFFECT OF INTERTIDAL EXPOSURE ON THE SURVIVAL AND EMBRYONIC DEVELOPMENT OF PACIFIC HERRING SPAM by BARRY CYRIL JONES B.Sc, University of British Columbia, 1965 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in the Department of Zoology We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA November, 1971 In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t of the requirements f o r an advanced degree a t the U n i v e r s i t y o f B r i t i s h Columbia, I agree t h a t the L i b r a r y s h a l l make 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 and study. I f u r t h e r agree 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 purposes may be granted by the Head o f my Department or by h i s r e p r e s e n t a t i v e s . I t i s understood t h a t c o p y i n g or 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 not be allowed w i t h o u t my w r i t t e n p e r m i s s i o n . Department o f ZOOLOGY The U n i v e r s i t y o f B r i t i s h Columbia Vancouver 8, Canada November 26, 1971. ABSTRACT Eggs of P a c i f i c herr ing were exposed to a i r for d i f f e r e n t periods of time i n s imulat ion of t i d a l e f fects on spawn deposits at varying beach heights . The maximum exposure range was 2/3 of a 2k hour day corresponding roughly to the exposure of eggs at k meters above mean low t ide on the B r i t i s h Columbia coast. Egg s i ze , spawning f i s h length , and egg clump s ize were examined as secondary factors modifying the effect of exposure. Incubation time dropped from 19 to 18 days with only two 2-hour periods of exposure per day and thereaf ter f e l l s lowly. It i s suggested that oxygen depr ivat ion tr iggered a hatching response for the i n i t i a l drop, whereas the gradual decrease was due to a higher a i r temperature increas ing metabolism. Hatching m o r t a l i t y rose s t ead i ly from an unexposed 1J% to yi% at maximum exposure time, with s i g n i f i c a n t l y higher contr ibut ions from eggs of smaller f i s h and smaller egg clumps. Larva l length at hatching for the unexposed eggs was 7*7 mm.5 lengths for a l l degrees of exposure were s i m i l a r (7% l e s s than for no exposure). Larva l weight (body plus yolk) remained r e l a t i v e l y constant (0.099 mg.) u n t i l the longest exposure period when i t dropped to O.O87 mg. This decrease coincided with s i m i l a r sharp trends i n incubation time and hatching m o r t a l i t y , and suggests a " c r i t i c a l point" near the upper experimental range of exposure, above which eggs stand l i t t l e chance of normal development or s u r v i v a l . Beach surveys to note poss ible egg s ize s t r a t i f i c a t i o n , although suggesting the deposi t ion of l arger eggs at the top l e v e l s , proved inconc lus ive , but point up the p o s s i b i l i t y that a heavy f i s h i n g pressure which reduces mean f i s h s ize might detr imenta l ly a f fec t po tent ia l stock recruitment v i a the i n t e r t i d a l exposure effect on the spawn. TABLE OF CONTENTS i i i Page ABSTRACT i LIST OF TABLES iv LIST OF FIGURES v ACKNOWLEDGEMENTS • v i i INTRODUCTION 1 MATERIALS AND METHODS 3 Spawner Characteristics Analyses.- 3 Exposure Laboratory Experiment 5 Egg Size Distribution Beach Surveys 9 RESULTS 10 Effects of Exposure 10 Incubation Time 12 Hatching Mortality 12 Larval Length 15 Larval Weight 15 Beach Stratification 18 DISCUSSION 18 LITERATURE CITED 26 APPENDICES 29 A - Apparatus Design 30 B - Raw Data 33 C - Spawner Correlations ^2 D - Computations Summary E - Statistical Analyses 52 iv LIST OF TABLES Table Page I Summary of experimental conditions 6 II Group means and standard deviations in the analyses 11 Appendix Table IA Spawner data l i s t 36 IIA Incubator data l i s t • 37 IIIA Computations for incubation time (days) 7̂ IVA Computations for hatching mortality {%) ^8 VA Computations for larval length (mm.) ^9 VIA Computations for larval weight (mg;..) 50 VILA. Computations for beach stratification of egg weight (mg.), showing beach height (m. ) 50 VIIIA Significance of differences within the total data 53 IXA Significance of differences between groups 5^ XA Significance of interaction 55 XIA Significance of differences between beach levels 56 LIST OF FIGURES v Figure Page 1 Relationship of beach height to exposure time. Data for Vancouver, B.C., (March, 1970) meaned from Straits Towing calendar 6 2 Relationship of incubation time to exposure time for total data 13 3 Relationship of hatching mortality to exposure time for total data 13 k Fish length effects in the relationship between hatching mortality and exposure time Ik 5 Clump size effects in the relationship between hatching mortality and exposure time Ik 6 Relationship of larval length to exposure time for total data 16 7 Egg size effects in the relationship between larval length and exposure time..... 16 8 Relationship of larval weight to exposure time for total data 17 9 Egg size effects in the relationship between larval weight and exposure time 17 10 Relationship of egg size to beach height at spawning, Bedwell Bay, April 20, 1970 19 11 Relationship of egg size to beach height at mid-incubation (8'days), Nanoose Bay, March 27, 1970 19 12 Relationship of egg size to beach height just after spawning (k days) and at hatching (16 days) for the same egg mass. The latter is for larvae as the eggs hatched en route to the lab. These samples taken at Icarus Point, March 17 and 29, 1971 20 LIST OF FIGURES (CONT.) Appendix Figure Page 1 A Tank set-up for each exposure time 32 2 A Cross-section of incubator in tank 32 3A Relationship of egg size to spawner length 4 3 4A Relationship of egg size to spawner weight with gonads removed 43 5A Relationship of egg size to spawner age 6 A Relationship of spawner length to age kk 7A Relationship of spawner weight with gonads removed to age 4 5 8A Relationship of spawner weight with gonads removed to length 4 5 ACKNOWLEDGEMENTS v i i I would l i k e to thank Dr. P .A. L a r k i n , my supervisor , of the Department of Zoology, Un ivers i ty of B r i t i s h Columbia, who gave me the opportunity , support from h i s Nat ional Research Council grant, and guidance i n th i s work over the past two years. The ass is tance of Dr. F . H . C . Taylor and the other members of h i s Herring Invest igat ion group of the F i s h e r i e s Research Board of Canada's B i o l o g i c a l S ta t ion , Nanaimo, i s a lso g r a t e f u l l y appreciated. They supplied me with the f a c i l i t i e s , the f i s h , and checked, cer ta in of my data. Thanks also go to Dr. N. G i l b e r t for h i s help in the set-up and use of h i s non-orthogonal ana lys i s of variance computer program and to Dr. D . J . Randall for h i s h e l p f u l c r i t i c i s m s of the manu- s c r i p t . Drs. G i l b e r t and Randall are of the Department of Zoology, Un ivers i ty of B . C . THE EFFECT OF INTERTIDAL EXPOSURE ON THE SURVIVAL AND EMBRYONIC DEVELOPMENT OF PACIFIC HERRING SPAWN INTRODUCTION The eggs of the P a c i f i c herr ing (Clupea p a l l a s i i V a l . ) are spawned i n and below the i n t e r t i d a l zone. Due to t h e i r adhesive nature, they become attached to c e r t a i n forms-of seaweed and are e s s e n t i a l l y immobile. For th i s reason most of them are subjected to regular periods of exposure and sub- mergence. Such condit ions cause considerable f l u c t u a t i o n i n the environment of the eggs and may a f fec t t h e i r s u r v i v a l and development. The ef fect of thi>s f l u c t u a t i o n i s os tens ib ly d i r e c t l y r e l a t e d to the height up the beach that the eggs are l a i d , and thus, the amount of time they are exposed. Within the spawning zone a var ie ty of egg s izes can be expected because each spawner produces a range of egg s izes (for example, for A t l a n t i c h e r r i n g , Clupea harengus, Hempel and Blaxter , 1 9 6 7 ) . In a d d i t i o n , every reproductive stock comprises a var ie ty of i n d i v i d u a l s d i f f e r i n g i n length, weight, and age, and several studies (Rannak, 1 9 5 8 ; B laxter and Hempel, 19^3) have shown that mean egg s ize i s a funct ion of s i ze and maturity . The adhesiveness of herr ing eggs also causes the formation of clumps when exposed to sea water. Such clumps are of d i f f e r i n g thickness and vary i n egg s ize and number. Hence, egg s i ze , f i s h s i ze , and clump s ize a l l 2 have some bearing on the poss ib le ef fects of environmental f l u c t u a t i o n r e s u l t i n g from exposure. The c h a r a c t e r i s t i c s most notably af fected are incubation time, hatching m o r t a l i t y , and l a r v a l length and weight at hatching. In th i s regard, Blaxter and Hempel (1963) noted that egg s i ze d id not a f fec t incubation time, whereas hatching m o r t a l i t y was found by other studies (Runnstrom, 19^1; McMynn and Hoar, 1953) to be d i r e c t l y re la ted to egg number. The larvae have been shown to be af fected by both egg and f i s h s i zes . For instance, Toom (1958) has demonstrated that l a r v a l s i ze i s d i r e c t l y r e l a t e d to egg s i ze , and Cushing and Bridger (I966) have noted that larvae from f i r s t spawners are l e ss v iab le than those from l a r g e r f i s h . In a d d i t i o n , i t has also been shown (Nagasaki, 1958) that fecundity i s d i r e c t l y r e l a t e d to spawner s i ze . Because f i s h i n g i n t e n s i t y reduced the mean s i z e , age, and numbers of spawners of B r i t i s h Columbia stocks of herr ing (Taylor , 1963) and North Sea h e r r i n g , Clupea harengus (Cushing and Br idger , 1966), then i t must fol low that mean egg s i ze a lso decreased. There would be fewer, smaller eggs produced than i n former years, and with a l e s ser chance of l a r v a l s u r v i v a l . The s u r v i v a l advantage accruing to a f i s h stock due to the presence of l a r g e r eggs and larvae has been pointed out by Marshall (1953)- If environmental fac tors operating i n the spawning zone are more detrimental to smaller eggs or the eggs from smaller f i s h , then there could be serious repercussions on recruitment p o t e n t i a l , 3 i . e . the number of immature f i s h a v a i l a b l e to enter the reproductive populat ion. Previous work on herr ing egg development has been concerned with condit ions for submerged eggs. This study- sought to examine incubation time, hatching m o r t a l i t y , and l a r v a l length and weight at hatching i n r e l a t i o n to varying degrees of exposure. The laboratory experiment was conducted and analyzed using as a d d i t i o n a l var iab les the effects of egg s i z e , f i s h s i ze , and clump s i z e . A beach survey was a l so undertaken to note poss ible egg s ize s t r a t i f i c a t i o n . MATERIALS AND METHODS The eggs used i n t h i s study were taken from spawning P a c i f i c herr ing of the Lower East Coast stock (inner southern Vancouver Is land region) of B r i t i s h Columbia, and the l abora - tory experiment was done at the F i s h e r i e s Research Board of Canada's B i o l o g i c a l Stat ion i n Nanaimo, B . C . Spawner C h a r a c t e r i s t i c s Analyses Forty female spawners were used to determine i f egg s i ze was r e l a t e d to f i s h s ize and maturity . The f i r s t 29 were taken by beach seine and held a l i v e i n l a r g e , we l l - f lushed hold ing tanks for one week p r i o r to use. The other 11 were obtained dead from l o c a l trawlers within 6 hours of capture and used i:mmedlately. A f t e r s t r i p p i n g the experimental eggs, the spawners were measured for standard length ( t ip of snout to end of ver tebra l column) and three or more scales plus 4 both o t o l i t h s were taken for age determinations. The gonads were then removed and the spawner wet weight recorded. The f i s h were then tagged and preserved i n 5$ formal in for poss ib le future reference. The age of each spawner was determined by reading the scales from the areas above and below the l a t e r a l l i n e between the rear of the g i l l cover and the front of the dorsal f i n (Tester, 1937). These were cleaned, dyed, and mounted on a glass s l i d e . The 11 trawl caught f i s h had very few scales , and hence, any scale was used. These ages were checked with the o t o l i t h s which had been cleaned and preserved i n 5$ forma- l i n . Samples of each spawners' gonads were immediately pre- served i n S% formalin when removed. This succeeded i n hardening and separating the eggs from each other and the ovarian t i s sue so that they could be e a s i l y counted. Sub- sequently, the gonad samples were broken up to re lease the eggs which were then thoroughly washed i n fresh water. F ive samples of 100 eggs were taken from each of two f i s h and put i n a drying oven for 24 hours at 50° Centrigrade^. Several p r i o r tests confirmed that there were no effects of pos i t ion of samples i n the dryer , the dryer handling capaci ty , the est imation 'Of residue weight, and the length of dry ing time. The samples were i n d i v i d u a l l y removed from the oven, weighed on a Cenco e l e c t r i c a l balance to the nearest 0.1 mg., weighed 1 These condit ions are the same as those used by Blaxter and Hempel (1963 ). again as a check, and then discarded. 5 Exposure Laboratory Experiment Five tanks (see Appendix A) simulated condit ions at d i f f erent beach l e v e l s (Figure 1) ranging from the contro l (0) which was continuously submerged, through 2, 4, 6, and 8 hours of exposure twice per day. These exposure times simulate a f ixed t i d a l cycle of roughly 2 meters amplitude (not found i n th i s area , but necessary as an experimental feature) . Each tank contained for ty incubators , and a l l were kept i n a small temperature-control led room under regulated condit ions (Table 1). From every female spawner approximately 100 eggs were s tr ipped into each of f i ve separate incubators . In th i s operat ion, clumping of the eggs was unavoidable, but an <$ attempt was made to produce the same clump form i n a l l incubators . The incubators were then simultaneously placed into a glass f e r t i l i z a t i o n tray containing a sperm so lu t ion and allowed to stand for 60 seconds. The sperm so lu t ion was prepared using 500 ml. of sea water and s u f f i c i e n t sperm from 2 or 3 males (to ensure v i a b l e sperm) to turn the water opaque. The incubators were transferred to another tray and gently f lushed with fresh sea water to prevent polyspermy and remove any excess organic matter which might decay i n the tanks. They were then transferred to t h e i r respect ive exposure tanks and kept submerged for 12 hours before the The small s ize and adhesiveness of the eggs prevented counting. In f a c t , i t was found that the mean was 132 eggs; standard deviat ion t kj,. 6 Exposure time twice per day (hr . ) Figure 1: Re lat ionship of beach height to exposure time. Data for Vancouver, B . C . , (March, 1970) meaned from S t r a i t s Towing calendar. Table 1: Summary of experimental condi t ions . Factor Mean Standard Dev.(SD) (1) Light (a) (b) • • Day length Intens i ty 13 hours 60 watt bulb at cm. above each 75 tank — (2) A i r : —Ta) (b) Temperature Relat ive humidity 1 1 . 7 ° C 65% to. 6° t5% (3) Sea Water* (a) Temperature (b) Oxygen (c) Flow rate (d) Depth 7.8° C 6.5 m l ./ I . 55ml. per min. per incubator 5 cm. +0.4° ±3 ml. 7 experimental condit ions were i n i t i a t e d . The a r t i f i c i a l environment (summarized i n Table I) was s i m i l a r to that recorded on the beach surveys during the experimental incubation per iod. An attempt was made to main- t a i n the laboratory temperature at 12° C. A maximum-minimum thermometer checked d a i l y gave a mean of 11.7° G; SD * 0.6°. The mean r e l a t i v e humidity determined by s l i n g psychrometer was 65%', SD * 5%> The day length was regulated by time clock and set at th i r t een hours (9 am to 10 pm) so that one exposure period was i n the l i g h t and the other i n darkness. The l i g h t source was a s ingle 60-watt incandescent bulb per tank. Each bulb had a white porce la in rear r e f l e c t o r and was suspended 75 cm. above the l e v e l of the eggs i n the center of the tank. The sea water or ig inated from the bottom of the l o c a l bay and ran continuously through the tanks at a mean rate of 55 m l • per minute per incubator; SD * 3 nil. When the tanks were f u l l , a l l the eggs were suspended at an equal depth of 5 cm. Several oxygen determinations were c a r r i e d out on the i n l e t and out le t waters by the Improved Winkler Method and a l l came to approximately 6.5 ml. per 1. This would suggest that with p l e n t i f u l oxygen i n the i n l e t waters and the open c i r c u l a t o r y system, oxygen was not a l i m i t i n g factor-^. Regular water temperature measurements y ie lded a mean of 7•8° C; SD - 0.4°. This resu l ted i n an a i r /water temperature d i f f e r e n t i a l of 4° C. 3 This was v e r i f i e d by a tank pos i t ion analys i s of the r e s u l t s using Dr. N. G i l b e r t ' s program. However, because the system was open and appropriate water sampling proved d i f f i c u l t , I would question the v a l i d i t y of these deter- minations, although not the conclusions drawn. 8 After 15 days the larvae "began to hatch. Throughout the hatching period collection was done immediately prior to exposure (10 am and 10 pm) of the eggs . Upon removal by large-mouth pipette, they were immobilized in a 1:50,000 solution of MS222 (Tricaine Methanesulfonate). This treatment caused the larvae to straighten out and stiffen. They were then preserved in 5% formalin. When larval emergence ceased, the incubators were cleaned out and the dead eggs counted-'. Prom this data the incubation time (from f e r t i l i z a t i o n to 50$ hatch) and mortality were determined. At convenient times during and after the experiment the larvae were counted and the lengths (from t i p of snout to end of t a i l ) of a l l measur- able larvae were determined by graduated microscopic eyepiece. This work took some 3 months, during which time a companion shrinkage test was run. When the measuring was completed, the test was terminated and a table of daily shrinkage correction values was computed and used to correct the mean larval length obtained for each incubator. The shrinkage was found to be only U-,2% over the entire three month measuring period. Once the larvae from each incubator had been counted and measured, they were a l l put into one v i a l . When a l l the incubators had been processed in this way, ten vials (incubators) at a time were taken, the larvae recounted, washed thoroughly in fresh water, and dried and weighed in Larvae did not hatch out during the exposure periods. The dead larvae were in many stages of development. 6 7 the same manner as for the spawner egg weights ' . Egg Size D i s t r i b u t i o n Beach Surveys A number of recent spawning s i t e s were examined during daytime low t i d e s . For purposes of comparison, the deter- mination of beach height was based on the datum establ ished by the sea l e v e l at the exact time of low t ide (as ind icated i n the Canadian Tide and Current Tables - #5, using Point Atkinson as a reference) . The sea l e v e l at t h i s time was used as sample area M, the middle region of f i v e beach l eve l s sampled on each survey. The bottom sample (B) was then taken i n as great a depth as p r a c t i c a l (about 1 meter), and another sample (L-low) taken halfway between these two (about 50 cm.). The ac tua l sample depths were determined with a graduated s t a f f . Two further samples were taken above M — T (top), as high as the spawn was deposited, and H (high), halfway between T and M. The heights of these were determined by clinometer and tape measure. The samples, taken i n 500 ml. j a r s , included as many eggs and the seaweed they adhered to as poss ib le . Environmental condit ions were also recorded at the spawning s i t e s . Among these were the a i r and sea water F i x a t i o n i n formalin over a three month period was shown to have n e g l i g i b l e ef fects on l a r v a l weight (-0.4$) and egg weight {-0.2%) by Blaxter and Hempel ( 1 9 6 6 ) . Larva l weight i n t h i s experiment means the t o t a l weight of the body and the yolk sac. 10 temperature, and r e l a t i v e humidity as determined by s l i n g psychrometer. These data were used as a guide for the exper i - mental regime. Upon re turning to the l a b , the age of the spawn was estimated (Outram, 1955)« the samples were preserved i n 5% formal in , and the beach l e v e l for each sample r e l a t i v e to mean low t i d e was ca l cu la ted . Later , the eggs were separated from the seaweed by trans fer to a one normal KOH so lu t ion which was then heated to 30° C. and allowed to stand for 2 h o u r s ® . The eggs and seaweed were then transferred to a 5% formalin so lu t ion again to harden for 24 hours before the seaweed was removed and discarded. This treatment not only loosened the eggs from the seaweed, but a l so from each other. The eggs were then thoroughly washed i n fresh water, and ten 100-egg samples were taken from each beach l e v e l for drying and weighing as per the spawner egg weight determinations. RESULTS Ef fec t s of Exposure Eggs from s ix of the trawl caught f i s h had 100^ morta l i ty i n a l l tanks. The data from these incubators was discarded on the grounds that the eggs were probably already d i s i n t e g r a t i n g when used. Data for one spawner from the beach seine group was discarded for the same reason. The net Q Procedure by word-of-mouth from herr ing researchers at the B i o l o g i c a l S ta t ion , Nanaimo, but s l i g h t l y a l t e r e d . 11 r e s u l t was data from 3 3 spawners. On cons iderat ion , the experimental data was d iv ided into three groups — noted as smal l , medium, and large . in the analyses (see Appendix D). The data were i n i t i a l l y analysed i n t o t a l to note the general trend of each c h a r a c t e r i s t i c i n r e l a t i o n to increased exposure time. They were then treated separately according to t h e i r groupings as noted above. Egg s i ze as determined from the preserved gonads was f i r s t examined for poss ible d i f ferences between groups. It was found of s ign i f i cance only i n l a r v a l length and weight (see Appendix E ) . The second analys i s examined the ef fects of f i s h length. Here hatching morta l i ty and l a r v a l weight were shown to be a f fec ted . Since f i s h length and weight are so h igh ly corre la ted (see Appendix C ) , the ana lys i s was not repeated for weight. The effect of age was not examined as the spawners were predominantly 3 -year o ld f i s h , with only a few 4 and 5 -year o lds . Because the egg number (clump s ize) was d i f f e r e n t for each incubator, a t h i r d test was run to see i f t h i s had any e f fec t . It proved n e g l i g i b l e for a l l c h a r a c t e r i s t i c s but hatching m o r t a l i t y . The mean group values for these three analyses are given i n Table I I . Table I I : Group means and standard deviat ions i n the analyses. Grouping Small Medium Large ( 1 ) Egg s ize (mg.) ( 2 ) P i sh length (mm.) ( 3 ) Clump Size (no.) 0 . 2 4 3 * 0 . 0 1 5 1 9 9 * 5 8 9 * 1 7 0 . 2 7 1 * 0 . 0 0 5 2 1 1±4 1 3 0 ± 1 2 0 . 3 0 0 * 0 . 0 1 5 223±6 1 7 5 * 2 9 12 Another analysis was performed to determine i f there was any interaction among egg size, fish length, and clump size. This was found to be non-significant in most cases for a l l factors and hence w i l l not be referred to further. These various analyses are discussed together for each of the variables examined. Incubation Time The relationship of incubation time to exposure time is shown in Figure 2. The control or unexposed incubators had a slightly greater than 19-day incubation period. The f i r s t exposure period (2 hours) showed an abrupt decrease of close to one f u l l day (p < . 0 1 ) . Thereafter, there i s only a gradual decrease through the remaining exposure periods, but the total decrease (from 2 to 8 hours) of 0.4 days is significant (p = . 0 1 - . 0 5 ) . Hatching Mortality As expected, the hatching mortality showed a continuous increase with increasing exposure time (Figure 3 ) . rising from 13$ in the control to 31$ in the 8-hour exposure period. For the total data, this is significant (p < .01)9 . Eggs from smaller f i s h had a higher mortality (Figure 4), but the effect was not s t a t i s t i c a l l y significant (p = . 0 5 - . 1 0 ) . Analysis of this small fis h data did not indicate which egg 9 A l l hatching mortality s t a t i s t i c a l tests were done on arcsin transformation of the percentage data. 13 19-5 • 17. 0 • 0 2 4 6 8 Exposure time twice per day (hr.) Figure 2 : Relationship of incubation time to exposure time for t o t a l data. 53%T 0 2 4 6 8 Exposure time twice per day (hr.) Figure 3 8 Relationship of hatching mortality to exposure time f o r t o t a l data. 40 14 > 5 •P •H H 03 P o g to •H -C o -p 03 m 30 20 10 • medium f i s h Figure 4: 8 ) 2 4 Exposure time twice per day (hr . ) F i s h length effects i n the r e l a t i o n s h i p between hatching morta l i ty and exposure time. - P o3 -p u o g faD fl •H .c o p 03 K 40 30 20 10 small clumps large clumps 6 2 5 6" 8" Exposure time twice per day (hr . ) Figure 5« Clump s ize effects i n the r e l a t i o n s h i p between hatching morta l i ty and exposure time. sizes within the group might be suffering greater mortality. Smaller egg clumps also had a significantly higher mortality (p < .01 for several exposure periods) than larger egg clumps (Figure 5 ) . Larval Length Larval length at hatching in relation to the exposure time (Figure 6) follows closely the pattern of incubation time. The i n i t i a l drop between the control and the 2-hour exposure periods from 7.7 mm. to 7-2 mm. is significant (p < . 0 1 ) . From exposure periods of 2 to 8 hours there was no further, decrease. Larvae were shorter (Figure 7) from smaller eggs, but this difference was not significant (p = . 0 5 - . 1 0 ) . Larval Weight The relationship of larval weight to exposure time (Figure 8) follows a concave curve, rising from 0.092 mg. to a high of 0.099 mg. at the 4-hour period, and f a l l i n g back to 0.087 mg. by the 8-hour period. None of the differences was s t a t i s t i c a l l y significant. For egg size groups (Figure 9) there was a pronounced (p < .01) relationship to larval weight. Fish length had similar effects (not shown), except that they were not sig- nificant (p = . 0 5 - . 1 0 ) . 8 . 5 1 6 Xi •p faO fl) I - H iH f-l 5 8 . 0 7 . 5 7 . 0 6 . 5 F i g u r e 6 : ) 2 4" 6 8 Exposure t i m e t w i c e p e r day ( h r . ) R e l a t i o n s h i p o f l a r v a l l e n g t h t o exposure t i m e f o r t o t a l d a t a . xi •p bD C 0 r-n rH cd l - H 8 . 5 8 . 0 7 - 5 7 . 0 6 . 5 s m a l l eggs- 0 F i g u r e 7 * Exposure t i m e t w i c e p e r day ( h r . ) Egg s i z e e f f e c t s i n t h e r e l a t i o n s h i p between l a r v a l l e n g t h and exposure t i m e . 17 s .p s: bO •H <D DS H ts rH 0.12 0 . 1 0 0. 08 0 . 0 6 Figure 8 : 0 2 4 6 8 Exposure time twice per day (hr.) Relationship of l a r v a l weight to exposure time for t o t a l data. 0.12 s 0 . 1 0 p Si 60 •H <D ts rH IS rH a 0. 08 o. 06 Figure 9: ~0~ large eggs 2 4 6 Exposure time twice per day (hr.) Egg size effects i n the r e l a t i o n s h i p between l a r v a l weight and exposure time. 8 1 8 Beach S t r a t i f i c a t i o n The beach survey done at the time of spawning (Figure 10) showed an increase i n egg weight with beach height. This trend was s i g n i f i c a n t (p < .01). By mid-incubation (Figure 11) the r e l a t i o n s h i p had disappeared, becoming convexly c u r v i l i n e a r with no s i g n i f i c a n t di f ferences between beach l e v e l s . Time- sequenced observations cons i s t ing of an ear ly (4 days) and a l a t e (16 days - hatching) stage for a s ing le egg mass was done to c l a r i f y t h i s problem (Figure 12). However, the l 6 - d a y sample was taken lower down on the beach and hatched en route to the laboratory . The l a r v a l weights obtained were assumed to be a r e f l e c t i o n of t h e i r former egg weights and were com- pared with the k— day sample on a r e l a t i v e bas i s . No s i g n i f i c a n t trends were ind ica ted . DISCUSSION The spawners used i n t h i s experiment were e s s e n t i a l l y a l l recent ly mature h e r r i n g . As such, the re su l t s found are only t r u l y app l i cab le to the spawn of these young f i s h . The exposure time imposed on the spawn ranged up to 2/3 of a day, and reduced incubation time, increased hatching m o r t a l i t y , and reduced l a r v a l length and weight. Poss ible explanations for some of these patterns are presented below. Incubation time dropped markedly when the eggs were f i r s t exposed, but thereafter decreased gradual ly with increased exposure time. The drop with only two 2-hour exposure periods per day may be due to oxygen depr iva t ion . In th i s regard, 19 0 . 2 4 h 0 . 2 2 bD -p W 0 . 2 0 0) bO bO W 0 . 1 8 MLT 0 3 . 0 1 .0 2 . 0 Beach Height (m.) Figure 1 0 : Re lat ionship of egg s ize to beach height at spawning, Bedwell Bay, A p r i l 2 0 , 1970. 0 . 2 4 r 0 . 2 2 b0 6 p bo 0 . 2 0 •H CD bD bO 0 . 1 8 M MLT 0 1.0 2 . 0 Beach Height (m.) 3 - 0 Figure 11 : Re lat ionship of egg s ize to beach height at mid- incubation (8 days) , Nanoose Bay, March 2 7 , 1 9 7 0 . 2 0 0.28 0 . 2 6 | 0.24 b0 w 0 . 2 2 0.20 0.14 0.12 0 . 1 0 (4 days) ( 1 6 days) MLT - 1 . 0 1 . 0 Beach Height (m.) 2.0 Figure 12 Relat ionship of egg s ize to beach height just a f t e r spawning (4 days) and at hatching ( 1 6 days) f or the same egg mass. The l a t t e r i s for larvae as the eggs hatched en route to the l a b . These samples taken at Icarus Point , March 17 and 2 9 , 1 9 7 1 . 21 V o l o d i n (1956) noted that there was an e r r a t i c but two f o l d increase i n oxygen requirements over the i n c u b a t i o n p e r i o d . In a d d i t i o n , Rannak (1958) found that hatching was i n i t i a t e d when eggs were t r a n s f e r r e d to lower oxygen pressures. Thus, whereas oxygen needs were s a t i s f i e d i n a i r and water when the embryos began development, j u s t p r i o r to hatc h i n g , when oxygen demand was much higher, the eggs may have been incapable of o b t a i n i n g adequate s u p p l i e s from a i r . A p o s s i b l e reason f o r lower oxygen a v a i l a b i l i t y i n a i r would be the impairment of the egg membrane by d e s i c c a t i o n , thereby r e s t r i c t i n g entry. As no l a r v a e hatched out during the exposure periods, i t might be that a more f l a c c i d nature of the membrane due to d e s i c c a t i o n prevented i t s r u p t u r i n g u n t i l the eggs were once more submerged and t h e i r membranes taut by i n t e r n a l pressure. In t h i s study, the beach survey eggs c o l l e c t e d a t 16 days were i n a d v e r t e n t l y made to hatch en route to the l a b o r a t o r y . As considerable l i v i n g organic matter was enclosed i n a very small space, the oxygen was undoubtedly depleted i n a very short time, and hence, could have i n i t i a t e d hatching of the eggs. The o v e r a l l gradual decrease i n in c u b a t i o n time i s l i k e l y due to the higher temperature encountered i n the a i r , promoting an inc r e a s e d metabolic r a t e . For the highest degree of exposure examined, the in c u b a t i o n time reached a minimum of 17.8 days. The r e d u c t i o n i n time at t h i s beach l e v e l was roughly 7%, over 5$ of which i s accounted f o r by the f i r s t exposure drop. This phenomenon provides a p o s s i b l e reason f o r d e p o s i t i o n of spawn i n the i n t e r t i d a l zone, which o b v i o u s l y must be of some advantage to the species s u r v i v a l , and that i s to attune hatching to 22 increased a i r and surface water temperatures which are associated with plankton product ion, the source of l a r v a l sustenance. In other words, as plankton production i s dependent on temperature, so a lso i s incubation time of herr ing spawn (Blaxter and Hempel, I 9 6 6 ) , and t h e i r coincidence would n a t u r a l l y be b e n e f i c i a l to the emerging larvae . 'Unfortunately, exposure of spawn a lso has several d i s - advantages. Among these are the increased hatching morta l i ty and detrimental e f fects on l a r v a l length and weight. The hatching morta l i ty on the spawning grounds was con- sidered by Taylor (1964) to average 37$ i f losses due to b i r d predation were not inc luded. This may be a t t r i b u t e d to i n v i a b i l i t y , overcrowding, and exposure to wave ac t ion and d e s i c c a t i o n . The r e s u l t s of t h i s experiment show a morta l i ty somewhat lower than t h i s (13 to 31%), and being dependent upon the durat ion of exposure. To some degree, wave ac t ion which was not an experimental feature could account for the d i f ference . What part i n v i a b i l i t y of eggs played cannot be deduced i n t h i s study. Eggs from small f i s h had a higher morta l i ty than those from l a r g e r spawners. Toom (1958) has demonstrated that l e s s v i a b l e larvae are produced by small f i s h , and hence, one might suspect that they were incapable of surv iv ing the r i g o r s of exposure or completing hatching manipulations. The egg density seems to have mixed e f fec ts . On the one hand large clumps might hinder f e r t i l i z a t i o n , l i m i t oxygen suppl ies , and promote waste product accumulation of the i n t e r n a l eggs. On the other hand, these same l a r g e r clumps would prevent 23 desiccation and mechanically protect (not applicable in this experiment) the inner eggs. It was found that the small egg clumps did in fact have a higher mortality than the larger ones. Undoubtedly though, as egg numbers get very large, the mortality w i l l increase many times and easily surpass that of the smaller clumps. This has been shown by Runnstrom (19^1). It would seem, then, that an optimum number of eggs per clump must exist for maximum survival. McMynn and Hoar (1953) have also come to this conclusion. It is possible that optimum clump size w i l l depend on the height up the beach at which the eggs are deposited. The survivors would be from some middle layer, deep enough to be protected, but not so buried as to be smothered — the depth of this layer depending on the degree of exposure. Whether or not clump size varies with fish size is also not known. As for the effect of exposure on the individual egg, Hamdorf (1961), working on trout eggs, suggests that a higher mortality could stem from introducing embryos which are beyond hatching size to lower oxygen regimes. In this case, they suffocate as the oxygen available is no longer sufficient to cover their minimum needs, and the flaccid exposure membrane prevents hatching. Blaxter and Hempel (I96D have also noted the possible mortality due to accumulation of waste when eggs are exposed. It seems probable that herring lay their eggs as high on the beach as the tide at spawning time w i l l allow. Referring to Figure 1, this would be at or near 4 meters above mean low tide, a place where exposure is lengthy and mortality is relatively 24 high . This d i s t r i b u t i o n i s i n fact borne out by Taylor (1964) and the beach samples taken i n t h i s study. It might even occur that an except ional ly high t ide during a spawning would r e s u l t i n eggs being deposited too high on the beach and hence, sub- jec t ing them to a much more severe degree of m o r t a l i t y . This could account for some part of year-c lass f l u c t u a t i o n i n numbers. On the other hand, l ay ing eggs high on the beach has been shown (Tester, 1942) to contribute to year-c lass s u r v i v a l . In t h i s case, the eggs on the lower beach and i n the water died for some unknown reason, while the higher eggs survived . As already suggested, exposure also has some ef fects on l a r v a l c h a r a c t e r i s t i c s . , The i n i t i a l drop i n l a r v a l length (7%) at f i r s t exposure i s expected, as e a r l i e r hatching would c e r t a i n l y mean l e s s time for l a r v a l growth or the conversion of yolk into body t i s sue . The lack of further decrease with a d d i t i o n a l exposure might wel l be due to the increas ing mean temperature enhancing the metabolic rate and hence, n u l l i f y i n g incubat ion time d i f ferences . A l t e r n a t i v e l y , these r e s u l t s may v e r i f y Hamdorf's ( I 9 6 I ) view that l a r v a l length i s d i r e c t l y r e l a t e d to the p r e v a i l i n g oxygen pressure and i s independent of exposure time. To some degree e a r l i e r hatching must also add to morta l i ty during the l a r v a l stage i f , as Rannak (I958) has s tated, exposure p r i o r to hatching readiness re su l t s i n premature and therefore l e ss v iab le larvae . This experiment ind icated that the smaller eggs y ie lded shorter larvae . It might be that these larvae are less v iab le than those from 25 larger eggs. This would further add to their disadvantages relative to larger larvae which have lesser food requirements, faster swimming speed, and a greater degree of thermal insula- tion (Marshall, 1953). Larval weight, on the other hand, (which includes yolk) might not be expected to change relative to exposure time. In fact, there is no change except at the highest degree of exposure where a decrease in weight begins. If there were any importance in the i n i t i a l increase in weight with exposure, this would lend support to Hamdorf's (1961) proposal that hatching weight may actually benefit from, exposure up to a point, possibly as a result of increased yolk u t i l i z a t i o n efficiency. In this experiment, the latter stage is manifest in a 12% decrease in weight with the greatest exposure. This drop may be due to in- efficiency of yolk conversion into body tissue. It coincides with similar sharper trends in both incubation time and hatching mortality, and suggests that a " c r i t i c a l point" in exposure time i s reached above which the environment i s so harsh that the eggs stand l i t t l e chance of contributing to year-class strength. This upper limit would seem to be near 14 hours of exposure per day, or roughly the 3-5 meter beach level during the spawning season. Eggs deposited above this level are not only subjected to a higher mortality, but also produce smaller, less viable larvae. From this study one might infer that most spawning is high up on beaches, where the larger eggs from larger fish are better f i t t e d to survive. In consequence, reduction in the 26 s ize of spawning f i s h implies a lower average rate of s u r v i v a l . An optimum clump s ize i s fur ther suggested, but i t s r e l a t i o n s h i p to f i s h s i ze or beach l e v e l i s unknown. Though the older and l a r g e r f i s h spawn f i r s t (Rannak, 1 9 5 8 ) , s ince the spawning period usua l ly l a s t s several days (and therefore twice as many t i d a l movements), the eggs of a l l f i s h may be evenly d i s t r i - buted over the spawning zone. The beach c o l l e c t i o n of eggs at spawning d id however ind icate that the l a r g e r eggs were further up the beach. Unfortunately , the other beach surveys were f a r l e ss i n s t r u c t i v e , and the trends are fur ther complicated by the increas ing morta l i ty with exposure and the d i f f e r e n t i a l morta l i ty due to f i s h and clump s i zes . Another source of confusion i s the poss ib le effects of wave ac t ion and predation by b i rds as noted e a r l i e r . In any event, a heavy f i s h i n g i n t e n s i t y which kept the i n d i v i d u a l f i s h s ize small would imply a decreased average rate of s u r v i v a l at higher l e v e l s of spawning. Thus, f i s h i n g pressure has a hidden dimension i n a lso reducing spawn s u r v i v a l . LITERATURE CITED Blaxter , J . H . S . , and G. Hempel ( I 9 6 D "Biologische Beobachtungen bei der Aufzucht von Heringsbrut", Helgoland. Wiss. Meeresunters. , 7 ( 5 ) : 2 6 0 - 2 8 3 . (F i sh . Res. Bd. Canada, Engl i sh t r a n s l a t i o n #708) Blaxter , J . H . S . , and G. Hempel (1963) "The inf luence of egg s ize on herr ing larvae (Clupea harengus L . ) " , J . Cons. E x p l . Mer, 2 8 ( 2 ) : 211-2-4-0. 2 7 Blaxter, J.H.S., and G. Hempel (1966) "Utilization of yolk by herring larvae", J. Mar. Biol. Assoc. U.K., 46 (2) : 219-234. Cushlng, D.H., and J.P. Bridger (1966) The Stock of Herring in the North Sea and Changes Due to Fishing, Min. Agr. Fish. Fd., Fish. Invest., Series II, Vol. 2 5 ( 1 ) : 123 pp., London. Hamdorf, K. (1961) "Die Beeinflussung der Embryonalund Larvalentwicklung der Regenbogenforelle (Salmo irldeus Gibb.) durch die Umweltfaktoren CVj-Partialdruck und Temperatur", Zeit. Verg. Physio., 4 4 ( 5 ) : 523-549. Hempel, G., and J.H.S. Blaxter (I967) "Egg weight in Atlantic herring (Clupea harengus L.)", J. Cons. Expl. Mer, 3 1 ( 2 ) : 17O - I95 . Marshall, N.B. (1953) "Egg size in Arctic, Antarctic, and deep-sea fishes", Evolution, 7 ( 4 ) : 328-341. McMynn, R.G., and W.S. Hoar (1953) "Effects of salinity on the development of the Pacific herring", Can. J. Zool., 31: 417-432. Nagasaki, F. (1958) "The fecundity of Pacific herring (Clupea pallasli) in British Columbia coastal waters", J. Fish. Res. Bd. Canada, 15(3)' 313-330. Outram, D.N. (1955) The Development of the Pacific Herring and Its Use  in Estimating Age of Spawn, Fish. Res. Bd. Canada, Pac. Biol. Stn., Circ. #40. Rannak, L.A. (1958) — in Russian. ("Quantitative study of the Baltic herring eggs and larvae in the northern part of the Gulf, of Riga and the principal factors in determining their survival"), Trudy VNIRO, 34: 7-18. (Fish. Res. Bd. Canada, English translation #238) 28 Runnstrom, S. (19^1) "Quantitative inves t igat ions on herr ing spawning and i t s yearly f luc tuat ions at the west coast of Norway", F l s k e r i d i r . Skr. Havundrsok., 6(7 ) : 71 PP« Tay lor , F . H . C . ( I 9 6 3 ) "The stock-recruitment r e l a t i o n s h i p i n B r i t i s h Columbia herr ing populations", Rapp. C.P.I.E.M., 15^1 279-292. T a y l o r , F . H . C . (1964) L i f e Hi s tory and Present Status of B r i t i s h Columbia Herr ing Stocks. F i s h . Res. Bd. Canada, B u l l e t i n #143, 81 pp. Tester , A . L . (1937) "Populations of herr ing (Clupea p a l l a s i i ) in the coastal waters of B r i t i s h Columbia", J . F i s h . Res. Bd. Canada, 3(2): 108-144. Tester , A . L . (1942) "A high morta l i ty of herr ing eggs", F i s h . Res. Bd. Canada, Prog. Rep. Pac . , 53* 16-19. Toom, M.M. (1958) — i n Russian. ("Experiments i n the incubation of B a l t i c herr ing eggs"), Trudy VNIRO, 34: 19-29- (Off ice of Tech. Serv . , U.S . Dept. of Commerce, Wash. 25, D . C . , USA, Engl i sh t r a n s l a t i o n #6l l ) Volodin , V . M . (1956) — i n Russian. ("Embryonic development of the autumn B a l t i c herr ing and t h e i r oxygen requirements during the course of development"), Voprosy I k h t i o l o g l l , 7- 123-133- (F i sh . Res. Bd. Canada, Engl i sh t r a n s l a t i o n #252) 29 APPENDICES 30 APPENDIX A - Apparatus Design The tank, f i t t i n g s , and tubing were a l l polyethylene. For each tank, the water inflow d iv ided into four separate compartments of ten incubators entering at the bottom rear (Figure 1A). During the exposure period i t flowed across the f l o o r under the incubators and out the bottom front contro l d r a i n , e x i t i n g through the e l e c t r i c a l valve . This valve was open only when:., energized and operated on a time c lock. During submergence the valve was closed and the water f i l l e d the tank, f lowing out the top front overflow. Emptying or f i l l i n g the tank took J or k minutes. The incubators (Figure 2A) were made from 3 mm. p l e x i - glass tubing (2.5 cm. ins ide diameter) open at the top. The bottom and the four mid- leve l s ide ports (1.25 cm. diameter) were covered with Nitex #253 monofilament nylon screen. The lower 1.25 cm. separated from the top which i t secured with a t i gh t f r i c t i o n - g r i p band. The reason for th i s was to al low easy s t r i p p i n g of the eggs onto the bottom screen. This whole uni t was bonded together using ethylene d i c h l o r i d e . Each tank compartment was d iv ided in h a l f h o r i z o n t a l l y by a p lex ig lass plate (secured by S i l i c o n e Sealant) through which ten holes had been d r i l l e d . The incubators f i t t e d through these holes and locked i n by bayonet mount so the changing water l e v e l d id not dis lodge them. The water was made to flow up through the eggs and out the s ide ports when submerged, never reaching the top of the tube. Due to t h e i r 31 demersal and adhesive nature, the eggs themselves remained attached to the bottom screen and d id not f l oa t f r e e l y i n the upper tube. The apparatus was run continuously for two weeks p r i o r to the experiment - f or adjustment of the environmental condit ions and the removal of poss ible leaching materia l which might a f fec t the eggs. Figure 2A: C r o s s - s e c t i o n of incubator i n tank. 33 APPENDIX B - Raw Data The data for the spawners (Table IA) i s l i s t e d according to the f i s h number, the order i n which they were used. Numbers 14, 30 to 34, and 39 were el iminated due to 100$ morta l i ty i n a l l incubators . Why the eggs from spawner #14 died i s not known. On examination they formed a hard mass with no sign of embryonic development. It i s poss ib le they may have been i n f e r t i l e or were i n the process of being reabsorbed when s tr ipped . The l a t t e r i s sa id to happen when spawners are kept for long periods i n holding tanks. The other s ix f i s h were from the trawl caught batch, and a l l the eggs d i s in t egra ted . So as not to a f fec t the other healthy eggs, these incubators were a l l removed halfway through the incubation per iod . Data for a t o t a l of 33 female spawners was l e f t for a n a l y s i s . Table IIA l i s t s the i n d i v i d u a l incubator data by ex- posure index. The Incubator number consists of the f i s h number followed by the exposure index and has the same order as the spawners. The zeros mean that there was no data and were used as computer sent ine l s only . This lack of data i s based on the fo l lowing c r i t e r i a : (a) Incubation time - i f l e s s than 20 eggs hatched, the d i s t r i b u t i o n seemed too disperse to pinpoint 50$ hatch. Pour values were rejected on th i s b a s i s . (b) Hatching morta l i ty - any incubator with an egg number l ess than 45 was considered inadequate f o r comparison 3k with means based on more eggs. This level i s approximately the lower boundary of the 95$ range of egg number and eliminated only one value. (c) Larval length - the mean number of larvae measured per incubator was 3k; standard deviation * 15- This number was much less than that for larval weight as many larvae were too bent or otherwise misshapen to measure accurately. If there were less than 10 measurable larvae, which again is near the lower 95$ range boundary, then the data was not used. It was thought that, since each incubator had a range in larval lengths, less than 10 had too great a chance of not truly representing the mean. In this case, 11 values were dis- carded, the lower numbers being due to few straight larvae or a high hatching mortality. The maximum number measured per incubator was limited to 100. (d) Larval weight - the sensitivity of the e l e c t r i - cal balance was the deciding factor here. Thus, anything less than 15 larvae was determined inadequate to yield a f a i r estimate of the mean. Similar to larval length, however, fewer numbers may not have been representative. The actual mean number used was 6l: standard deviation - Ik. Here also the maximum number used from each incubator was 100 larvae. Hatching mortality again played a part in this elimination which involved 11 values. (e) Definite erratic values - there were only two rejections of this nature, and both were for larval weight. These must have been handling mistakes as the weights were far removed from the rest of the larval weight determinations. In fact, they were actually in excess of the egg weights noted for their respective spawners. TABLE IA. SPAWNER DATA LIST 36 FISH LENGTH WEIGHT AGE EGG WEIGHT NUMBER (MM.) ( GM. ) ( YR. ) (MG. ) X 202. 86. 3. 0.2228 2 218. 105. 3c 0.2884 3 222. 102. 3. 0.2564 4 205. 84. 3. 0.2182 5 194. 72. 3. 0.2564 6 214. 92. 3. 0.2526 220. 110. 4o 0.2806 8 205. 81. 3. 0.2682 9 204. 83. 3. 0.2668 10 218. 98. 3. 0.2554 11 217. 110. 3. 0. 2474 12 213. 97. 3. 0.2776 13 2U1. 79. 3. 0.2872 15 193. 67. 3. 0.2748 16 234. 134. 5. 0« 2876 17 192. 67. 3. 0.2478 18 231. 127. 4. 0.3204 19 205. 85. 3. 0.2640 2U 232. 128 • 5. 0. 29 /0 21 217. 110. 4. 0.2636 22 213. 103. 3. 0.2558 23 203. 76. 3. 0.2926 24 201. 79. 3. O i 2738 25 219. 107. 3. 0.3204 Zb 2U /. 8 / • i i . 0.2 726 27 216. 97. 4. 0.3196 28 221. 100. 4. 0.2966 29 213.' 86 • 3. 0.2752 35 200* 74. 3. 0.2658 36 215. 88. 4. 0.3068 3 / 20 /. / / . 3. 0.2 /58 38 197. 76. 3. 0.2380 40 215. 98. 4. 0.2212 37 TABLE I I A. INCUBATOR DATA LIST (ZERO VALUES MEAN NO DATA = COMPUTER SENTINEL ONLY) CONTROL DATA INCUBATOR INCUBATION HATCHING LARVAL LARVAL NUMBER NUMBER TIME MORTALITY LENGTH WEIGHT OF (DAYS) (PER CENT) (MM.) (MG.) EGGS 10 1 9 . . 15 1 3 . .3 7, .3 1 0 . 0 0 0 2 5 5 . 20 19* • 18 12 . 11 7. .20 0. 0 0 0 1 3 2 * 30 18. .82 3. .6 7. 4 4 0 . 0 6 6 1 6 6 . 4 0 19. >Q5 5. 9 7. .36 0 . 0 5 6 1 0 2 . 50 19. .76 1 4 . .5 7. .17 0 . 0 6 8 166 e 60 19. .07 1 2 . 3 6. .91 0 . 0 5 0 65 . 70 19. .36 1 7 . .4 7. .22 0 . 0 8 4 9 2 . 80 19 • 22 1 9 . 0 7. .35 0 . 0 8 3 7 9 . 90 18. .71 1. .8 7« .11 0 . 0 6 6 1 1 2 . 1 0 0 19. i 0 4 1 6 . »1 6. .89 0 . 1 1 7 5 6 . 1 1 0 18 • 70 3 . . 2 7. .15 0 . 0 7 6 2 1 6 . 12U IB • 62 1 9 . . 3 (i .19 0 . 0 8 1 ii?U . 130 18. .95 1 6 . .2 7. .30 0 . 0 8 5 1 3 6 . 150 19. . 19 4 2 . .4 7. .38 0 * 0 9 2 118 . 1 6 0 2 0 . .15 2 3 . .7 7. .7 5 0 . 0 8 7 1 5 6 . 1 7 0 19. .05 2 6 . ,0 6. 80 0 . 0 7 4 1 0 4 . 1 8 0 18. .48 1 3 . .6 7. .98 0. 105 8 1 . 1 9 0 19. .12 0. . / / .B5 0 . 0 8 2 142 . 2 0 0 18. .91 3. .6 7. 90 0 . 0 9 8 138 . 2 10 19 .32 6. .5 8. .40 0 . 0 9 9 1 0 7 . 2 2 0 18 .66 1 0 . . 3 7. .85 0 . 0 9 3 1 2 6 . 2 3 0 19 .59 1 3 . .4 8. .2 1 0. 109 9 7 . 24 0 18. .75 6. .5 7. 99 0 . 1 0 2 1 5 5 . 18 .64 3 . 6 8 .49 0. 123 1 1 1 . 2 6 0 18 i 7 6 4 .3 8 .33 0. 106 1 8 5 . 2 7 0 18 .79 6 .3 8. .2 2 0 . 1 2 1 1 4 4 . 2 8 0 19 .72 7 .2 8. .15 0 . 1 1 3 1 6 6 . 2 9 0 19 .91 7 .3 8 .27 0.108 1 9 3 . 3 5 0 19 .50 17 .4 8 .28 0.114 1 2 1 . 36U 19 .5 3 IV . 2 8 .8 2 0 . 1 2 / . ftit 3 7 0 19 .83 2 1. .7 8 .19 0. 120 1 0 6 . 3 8 0 19 .50 2 6 . .9 8. .28 0 . 0 8 8 1 6 7 . 4 0 0 19 » 15 14. .6 7, .96 0 . 0 7 2 89 . T A B L E I IA (CONTINUED) 38 2 HOUR DATA INCUBATOR INCUBATION HATCHING L A R V A L LARVAL NUMBER NUMBER TIME M O R T A L I T Y LENGTH WEIGHT OF (DAYS) I PER CENT) (MM.) (MG.) EGGS 12 18. .00 2 9 . .2 7< .07 0 . 054 2 5 0 . 22 1 8 i .30 1 9 . . 1 It 07 0* 104 1 5 7 . 32 18. .25 18 . .2 6< 89 0 . 0 7 6 1 3 7 « 42 1 8 . .33 5 < 1 6« 92 0 . 0 8 9 1 5 6 . 52 1 8 . .33 2 6 . 7 6. .64 0 . 0 9 0 1 3 1 . 62 18. .29 3 < .1 6. 96 0 . 0 8 0 9 8 . 72 18. .28 2 0 . .5 It 06 0 . 100 1 2 7 . 82 18. .38 18. .3 6. .79 0 . 0 8 0 1 3 1 . 92 18. .04 4i 0 6. .87 0 . 0 7 0 1 0 1 . 102 18. . 13 8« 5 6. .74 0 . 107 1 4 2 . 112 18. . 14 1. .8 6« 89 0 . 1 0 3 1 7 0 . 122 18. .34 36 . .4 6. .51 0 . 0 8 1 1 5 4 . 132 18. .06 44 . .3 6. .45 0 . 0 8 3 7 9 . 152 0. .00 76 . > 1 0< .00 0 . 0 0 0 4 6 . 162 18. .20 3 1 . .9 6. .50 0 . 0 9 0 9 4 . 172 18. . 10 2 1 . 0 6< .33 0 . 0 7 9 1 4 3 . 182 17. .61 3. ,7 6. 90 0 . 0 9 8 8 1 . 192 18. .00 4. .8 6. .68 0 . 0 8 4 1 4 7 . 202 18. .86 8. .3 7. .93 0 . 1 2 0 1 5 6 . 212 18. .04 7. .5 6. .69 0 . 0 9 7 9 3 . 222 17. .99 2. 7 6. .82 0 . 0 8 5 1 1 0 . 232 18. .26 13. 7 7. .11 0 . 102 9 5 . 242 18. .08 13. 9 6. .72 0 . 0 9 8 1 0 1 . 252 17. .46 18. .3 7. .5 1 0 . 1 2 2 131 e 262 17 .57 1. .4 7. .98 0 . 1 3 1 1 4 5 . 272 17 .85 10. .1 7. .92 0 . 1 5 1 148 . 282 17. .74 0. .6 8< .00 0 . 1 0 9 1 6 8 . 292 18 .53 5. 9 8 .06 0 . 1 0 1 2 7 1 . 352 18. .25 10. .4 8. .07 0 . 1 1 4 1 7 3 . 362 18 .50 54 . .5 8. .03 0 . 1 3 1 1 0 1 . 372 18 .51 16. .8 8 .09 0 . 1 2 0 1 1 3 . 382 18. .57 15. .4 7, . 89 0 . 0 8 6 2 4 7 . 402 18 .47 34. .3 8 .14 0 . 0 6 7 6 7 . TABLE I IA (CONTINUED) 3 9 4 HOUR DATA INCUBATOR INCUBATION HATCHING LARVAL LARVAL NUMBER NUMBER TIME MORTALITY LENGTH WEIGHT OF (DAYS) (PER CENT) (MM.) (MG.) EGGS 14 18.19 10.0 6.96 0.077 201. 24 18.67 18.5 6.71 0.112 135. 34 18.10 8.9 6.82 0.084 157. 44 18.15 16.5 6.91 0.083 164. 54 18.30 45.7 6.79 0.075 70. ~6Tf 18.08 9~T7 /.20 0.0 /4 TU3T 74 18.28 31.0 7.13 0.108 113. 84 18.05 11.8 7.37 0.076 127. 94 17.65 10.3 7.24 0.067 97. 104 18.09 20.4 6.90 0.120 142. 114 18.35 7.9 6.75 0.091 140. T7̂ + 18.30 T3T5 7T1J+ U. 130 125 . 134 0.00 80.8 0.00 0.000 78. 154 18.33 46.8 7.19 0.076 111. 164 18.61 32.8 7.16 0.107 122. 174 18.37 33.1 6.76 0.086 . 136. 184 18.23 20.1 7.34 0.131 144. T74" 18.21 Zf77i 7TCT5 0.089 HT3T 204 0.00 0.0 0.00 0.000 35. 214 17.97 42.7 6.82 0.090 82. 224 17.58 6.1 7.07 0.091 131. 234 18.45 22.1 7.22 0.101 122. 244 18.03 17.7 6.92 0.098 96. "254 17.88 T5T3 679~9 0.114 TW7 264 17.41 2.0 6.82 0.100 152. 274 17.69 3.3 6.92 0.111 152. 284 17.98 17.0 7.58 0.144 176. 294 18.70 2.6 7.82 0.112 190. 354 16.79 30.1 7.53 0.112 173. "36~4 18.48 34T5 0T0~Q~ 0.000 7~8T 374 17.63 21.1 7.76 0.123 90. 384 16.43 7.3 8.00 0.091 151. 404 18.44 42.3 0.00 0.000 71. T A B L E I I A ( C O N T I N U E D ) 40 6 HOUR D A T A I N C U B A T O R I N C U B A T I O N H A T C H I N G L A R V A L L A R V A L N U M B E R N U M B E R T I M E M O R T A L I T Y L E N G T H W E I G H T O F ( D A Y S ) ( P E R C E N T ) ( M M . ) ( M G . ) EGGS 1 6 1 7 . . 9 3 3 5 . . 7 6 . 9 4 0 . 0 6 3 1 4 0 . 2 6 1 8 . 4 4 3 . 0 7 . . 0 2 0 . 1 0 6 1 9 9 . 3 6 1 7 . 9 6 1 4 . . 5 6< . 7 5 0 . 0 6 9 1 3 1 . -+6 1 8 . 2 7 1 2 . . 5 6 . . 5 4 0 . 0 7 6 1 2 8 . 5 6 1 8 . 2 1 4 0 . 0 6 . . 3 5 0 . 1 1 2 8 5 . 6 6 1 8 . 3 1 1 0 . . 9 6 . . 6 6 0 . 0 8 2 1 2 9 . 7 6 1 8 1 1 8 1 1 . . 2 6 . . 7 4 0 . 0 9 0 1 1 6 . 8 6 1 8 . 0 2 1 6 . 9 6 . 8 7 0 . 0 7 6 1 4 8 . 9 6 1 8 . . 0 6 1 1 . . 1 6< 4 0 0 . 0 8 8 1 1 7 . 1 0 6 1 8 . . 2 4 1 4 . . 4 7 . . 1 2 0 . 1 2 7 9 7 . 1 1 6 1 8 . . 6 6 3 4 < 7 6 . . 4 9 0 . 0 7 3 1 1 8 a 1 2 6 1 8 . 3 6 2 0 . 2 6 . 6 4 0 . 0 9 0 1 3 0 . 1 3 6 1 8 . . 0 2 7 4 . . 2 O i 0 0 0 . 0 0 0 8 9 . 1 5 6 1 8 . 2 5 7 3 . 0 0 . . 0 0 0 . 0 0 0 1 1 1 . 1 6 6 1 8 . . 7 9 3 9 . 8 7« 0 6 0 . 1 0 2 1 2 3 . 1 7 6 1 8 . 4 8 1 0 i . 2 6 . . 5 2 0 . 0 7 0 1 5 7 . 1 8 6 1 7 . . 9 8 8 . 8 7« . 3 4 0 . 1 2 4 8 0 . 1 9 6 1 7 . . 9 6 6 . . 6 6 . . 9 1 0 . 0 8 9 1 5 2 . 2 0 6 1 8 . . 5 2 2 4 . 7 7 . 0 1 0 . 1 0 4 1 7 0 . 2 1 6 1 8 . . 3 9 4 0 . 0 7 . . 4 3 0 . 1 0 6 1 3 0 . 2 2 6 1 6 . . 7 6 1 0 . 9 7 . . 3 3 0 . 0 8 8 1 7 5 . 2 3 6 1 8 . . 6 1 3 7 . . 3 7 . 8 7 0 . 1 1 8 1 5 0 . 2 4 6 1 8 . . 5 4 2 0 . 0 7 . . 5 7 0 . 1 1 4 1 8 0 . 2 5 6 1 7 . . 8 2 6 . . 3 7 . 8 9 0 . 1 2 1 1 5 9 . 2 6 6 1 7 . . 6 9 2 . . 4 7 . 7 9 0 . 1 0 7 1 6 7 . 2 7 6 1 7 . . 6 6 1 . . 3 7« 8 7 0 . 1 2 5 1 5 2 . 2 8 6 1 7 . . 9 2 1 3 . 9 8 . 0 5 0 . 1 4 6 1 8 7 . 2 9 6 1 7 • 8 1 2 . . 4 8 . . 1 0 0 . 1 1 0 1 6 7 . 3 5 6 1 7 . 6 9 1 3 . . 1 8 . . 0 7 0 . 1 1 3 1 4 5 . 3 6 6 1 8 • 6 3 5 3 . . 1 0< . 0 0 0 . 1 0 8 8 1 . 3 7 6 1 7 • 6 4 2 6 . . 8 8 . . 0 8 0 . 1 1 7 1 1 2 . 3 8 6 1 6 • 7 6 2 5 « 9 7 . . 6 0 0 . 0 8 7 1 3 5 . 4 0 6 1 7 • 6 4 4 9 . . 5 7 . 4 8 0 . 0 7 7 1 0 7 . TABLE I IA (CONTINUED) 4 l 8 HOUR DATA INCUBATOR INCUBATION HATCHING LARVAL LARVAL NUMBER NUMBER TIME MORTALITY LENGTH WEIGHT OF (DAYS) (PER CENT) (MM.) (MG.) EGGS 18 16. .86 10. .3 7. 95 0. . 046 117. 28 17. .36 24. .4 7. .48 0. , 106 205. 38 17, .51 58. .6 7. 9 1 0, .055 70 . 48 17. .92 15. .6 6. 27 0. 060 135. 58 17. .58 4 3. 4 6. .71 0. .000 99. 68 171 .68 31. .6 fi 02 0. .000 57. 78 17. .53 3. .6 6c 66 0< .055 111. 88 17. .66 18. .7 6. .63 0. 075 123* 98 17. .54 3. .4 6« 77 0. .045 119. 108 18 .36 9. .6 6. .77 0, .110 230. 118 17. .63 29. .9 6. .45 0< ,055 177. i2b 1 / .52 30. U 6. .16 O i ,05 / iUU * 138 17. .37 70. .8 0< .00 0. ,000 89. 158 18. .49 25. .0 6< 86 0< .070 52. 168 17. .60 35. .6 6. .91 0. ,065 101. 178 17 .62 42 < .2 6. 81 0. .044 83. 188 17 .65 28< .8 6. .93 O i , 102 118 . 198 17 . 58 3 i . V b i .84 UI >UtiU i y 2 . 20 8 17. .57 36 . 5 6. .95 O i ,072 178. 218 0 .00 73. .7 0, 00 OI ,000 57. 228 18. .27 14. .2 6, .76 O i ,110 141. 238 18 .38 14 .3 7. .16 OI ,090 98 » 248 18 .30 16. .7 7. .0 1 0 ,114 H4o 258 1 / .68 2 1 > 1 1 .63 0 » 136 152 . 268 17 .70 1 .8 l i .49 0< » 102 226. 278 17 .68 26 .3 l i ,47 0 . 133 167. 288 17 .80 26. .0 7 ,66 0 .113 192. 298 17 .88 20 .4 7< ,60 0 .112 211. 358 18 .59 1 1 .6 7. ,14 0 .115 138 . 18 • SU 6 7. y b< >uy 0 . 120 112. 378 18 • 50 48. .9 8. ,04 0 . 120 92 • 388 0 • 00 94 .9 0. ,00 0< ,000 158. 40 8 17 .67 39 .8 7 .38 0 .090 113. APPENDIX C - Spawner Corre la t ions 42 A comparison of the various experimental spawner c h a r a c t e r i s t i c s l e d to the fo l lowing observations: The egg s i ze was found to be weakly corre la ted to f i s h length (Figure 3 A ) , f i s h weight (Figure 4A), and to f i s h age (Figure 5A). On the other hand, f i s h length (Figure 6k) and f i s h weight (Figure ?A) were more s trongly re la ted to f i s h age, and the r e l a t i o n s h i p of f i s h length to f i s h weight (Figure 8A) was very h ighly corre la ted . From th i s information, i t was decided that egg s ize and f i s h length would be used as bases for analyzing the incubator data. The use of both f i s h weight and length would have been redundant due to t h e i r high a s s o c i a t i o n . Length was se lected as these measurements were more exact; weight involved poss ible v a r i a t i o n i n moisture content and vest iges of gonads (which were removed for th i s determination since indeterminable amounts of eggs were already miss ing) . The use of age was re jec ted because of the very narrow and skewed d i s t r i b u t i o n of values . In a d d i t i o n , due to the poor c o r r e l a t i o n of f i s h length and egg s i z e , i t seemed necessary to use both these approaches to the data. 0.32 o © o 43 0.30 g> 0.28 •P «> 0.26 H-i 0) bO $ 0.24 0.22 190 ' 2 0 0 ' 2 1 0 ' 2 2 0 ' 2 3 0 Spawner Length (mm.) Figure 3A» Relat ionship of egg s ize to spawner length. 240 0.32 0.30 !? 0.28 p §0.26 <D .3 bO $0.24 0.22 © _ / / 1 1 1 1 1 1 1 1 — ^ 6 0 80 1 0 0 120 Spawner Weight (gm.) Figure 4 A : Re lat ionship of egg s i ze to spawner weight with gonads removed. 140 0 . 3 2 0 . 3 0 g> 0.28 -p «> 0.26 'H <D bO M 0.24 0.22 o o 3 44 Spawner Age (yr . ) Figure 5A: Relat ionship of egg s i ze to spawner age. 240 r Spawner Age (yr. ) Figure 6As Re lat ionship of spawner length to age. 140 Spawner Age (yr.) Figure 7 A : Relationship of spawner weight with gonads removed to age. 46 APPENDIX D - Computations Summary These tables summarize the means and standard deviations of a l l the analyses made in this study. For the experimental work, there i s a separate table for each of the characteristics examined, thus incubation time may be found in Table IIIA, hatching mortality in Table IVA, and larval length and weight in Tables VA and VIA respectively. The layout is by exposure index for the total data and for the groupings of egg size, fish length, and clump size. The number of data re- presented by each mean is dependent upon the c r i t e r i a l a i d out in Appendix B. Maximally, i t should be 33 for the total data and 11 each for the groupings. In fact, i t i s found that a minimum of 28 for totals and 7 for groups exists, but with most data being close to the maximum level. The egg weights for the beach stratification surveys (Table VIIA) are arranged by beach level and the collection time relative to the incubation stage of the spawn. The height above mean low tide that the sample was taken i s also shown. The means are based on 10 subsamples per beach level throughout. It should also be pointed out that the weights for the collection done at 16 days are for larvae because the eggs hatched on the way to the laboratory for preservation, and thus can be compared to the other collections on a relative basis only. Table IIIA: Computations f o r incubation time (days). Exposure time twice per day (hr. ) Charact e r i s t i c 0 2 4 6 8 (1) Total data 19.16 * 0.42 18.1? + 0.31 18.05 + 0.50 18.07 + 0.47 17.81 + 0.41 (2) Egg size Small 19.09 + 0.32 18.24 + 0.19 18.01 0.57 17.93 + 0.64 17.71 + 0.42 Medium 19.18 + 0.44 18.17 0.29 17.92 + 0.52 18.04 + 0.31 17.98 + 0.44 Large 19.21 + 0.51 18.10 + 0.41 18.25 0.34 18.23 + 0.38 17.74 0.37 (3) Fish length Small 19.22 + 0.34 18.21 + 0.18 17.86 + 0.70 18. 05 + 0.51 17.84 + 0.57 Medium 19.14 + 0.45 18.22 + 0.32 18. 06 + 0.42 17.88 + 0.51 17.90 + O.36 Large 19.12 + 0.50 18.09 + 0.38 18.22 + 0.27 18.26 + O.32 17.67 + 0.27 (4) Clump size Small 19.22 O.36 18.15 + 0.26 18.10 + 0.32 18.14 + 0.33 17-82 0.44 Medium 19.00 + 0.29 18.09 + 0.33 18.27 + 0.30 18.10 + 0.55 17.86 0.51 Large 19.26 + O.56 18.26 + 0.33 17-78 + O.67 17.96 + 0.53 17.72 + 0.26 Table IVAs Computations f o r hatching mortality ($). Exposure time twice per day (hr.) Characteristic 0 2 4 6 8 (1) Total data 13.0 + 8.9 17..8 + 16.8 21.5 ± 17.1 23.3 + 19.2 31.2 ± 22.0 (2) Eftfi s i z e Small 13-3 + 7.9 15.1 + 11.7 18.9 + 14.7 23.6 + 14.2 35.5 + 25.3 Medium 13.4 + 12.3 17.8 + 21.7 18.5 ± 15.^ 21.3 + 20.4 25.8 + 20.9 Large 12.4 + 6.6 20.5 I6.9 27.5 ± 20.9 24.9 + 23.6 32.3 + 20.5 (3) F i s h length Small 17.9 + 10.9 24.8 + 20.2 28.7 ± 22.2 32.7 ± 22.8 31-9 ± 28.6 Medium 11.1 + 6.9 15.9 + 17.8 14.2 ± 13.6 17.9 + 18.3 30.0 ± 18.1 Large 10.1 + 7.0 12.6 + 9.7 21.5 + 11.0 19.2 + 13.^ 31.6 ± 20. 0 (4) Clump size Small I6.3 + 5.3 26.1 + 24.3 35.2 + 21.6 36.1 + 24.2 43.1 + 18.7 Medium 11. 0 ± 11.8 14.3 + 8.5 19.8 9-5 24.4 + 11.7 21.0 + 18.8 Large 11.8 ± 8.4 12.9 + 11.3 10.7 ± 8.5 9.2 + 7.7 29.5 23.9 Table VA: Computations for l a r v a l length (mm.). Exposure time twice per day (hr . ) C h a r a c t e r i s t i c 0 2 4 6 8 (1) Tota l data 7.72 0.55 7.19 + 0.60 7.13 + 0.34 7.22 ± 0.57 7.12 ± 0.52 (2) Egg s i ze Small 7-37 + 0.48 7.03 + 0.53 7.02 + 0.37 6.89 0.43 7.00 + 0.57 Medium 7.85 + 0.50 7.25 + 0.70 7.24 + 0.35 7.39 + 0.64 7.05 0.54 Large 7-93 + 0.53 7.32 + 0.60 7.13 + 0.27 7.43 + 0.49 7.29 0.44 (3) F i sh length Small 7-56 + 0.53 6.99 + 0.57 7.20 + O.38 7.13 + 0.66 7.00 0.40 Medium 7.90 + O.56 7.46 + 0.67 7.19 + O.36 7.34 0.62 7.19 0.64 Large 7.69 + 0.54 7.11 + 0.50 7.02 + 0.28 7.17 + 0.48 7.13 + 0.49 (4) Clump s ize Small 7.61 ± 0.66 7.04 + 0.59 7.13 + 0.33 7.00 + 0.61 7. 06 0.59 Medium 7.82 + 0.50 7.05 + 0.57 7.05 + 0.24 7.13 0.53 7.05 + 0.56 Large 7.73 + 0.49 7.48 + 0.59 7.22 + 0.43 7.46 0.53 7.23 0.44 Table VTAi Computations for l a r v a l weight (mg.). Exposure time twice per day (hr . ) C h a r a c t e r i s t i c 0 2 4 6 8 (1) Total data o. 092 + 0.020 O.O96 + 0.020 0.099 + 0.019 0.099 ± 0.020 0.087 + 0. 028 (2) Egg s i ze Small 0.075 + 0.019 0.083 + 0. 014 0.087 + 0.013 0.083 + 0.019 0.071 + 0.027 Medium 0.095 + 0.016 0.097 + 0.019 0.097 0.020 0.100 + 0.014 0.088 + 0.026 Large 0.105 ± 0.016 0.109 0.019 0.115 + 0.014 0.114 0.015 0.099 + 0. 028 (3) F i s h length Small 0.088 -± 0.016 0.085 + 0.016 0.085 + 0.014 0.093 + 0. 021 0.074 + 0.029 Medium 0.092 ± 0.026 0.101 ± 0.027 0.101 ± 0. 018 0.097 ± 0.016 0.098 ± 0.025 Large O.O96 ± 0.018 0.102 ± 0. 012 0.110 ± 0.018 0.106 ± 0.023 0. 086 ± 0.029 (4) Clump s ize Small 0.090 + 0.026 0.091 + 0. 018 0.086 + 0.019 0.101 + 0. 020 0.071 + 0.025 Medium 0.097 + 0.018 0.097 + 0.019 0.104 0.017 0.089 0.018 0.084 0.029 Large 0. 089 + 0.016 0.101 + 0. 024 0.101 + 0.019 0.107 + 0.020 0.101 0.025 Table VIIA: Computations for beach s t r a t i f i c a t i o n of egg weight (mg.), showing beach height (m.). Time and place of sample Sample region Bottom Low Middle High Top (1) Spawning Bedwell Bay, 20/4/70. Mean Std. Dev. Height 0.170 0.004 0.12 0.205 0.013 0.92 0.209 0. 014 1.71 0.227 0.007 2.53 0.232 0.010 3.33 (2) Post-spawning (4 days) Icarus Pt., 17/3/71. Mean Std. Dev. Height 0.239 0.015 0.21 0.237 0.012 0.70 0.248 0.016 1.16 0.240 0.012 1.37 0.220 0. 011 1.68 (3) Mid-incubation (8 days) Nanoose Bay, 27/3/70. Mean Std. Dev. Height 0.205 0.007 -0.24 0.200 0.009 0.46 0.200 0.009 1.16 0.203 0.011 1.86 0.210 0.007- 2.56 (4) Hatching (16 days) (larvae) Icarus Pt., 29/3/71. Mean Std. Dev. Height 0.127 0.005 -0.37 0.130 0.005 -0.03 0.117 0.003 0.27 0.125 0. 002 0.58 0.126 0. 004 1.04 52 APPENDIX E - Statistical Analyses The original number of spawners was a r b i t r a r i l y set at forty (with five exposure periods) so that, with possible rejections, a good range of differences in egg and fis h sizes could be obtained. One-way analyses of variance were used on the data, and the following symbols have been employed to indicate the results: (—) not significant ( 0 ) significant at p = .05 - .10 ( * ) significant at p = .01 - .05 (**) significant at p < .01 Due to unequal replicate numbers, Scheffe's method was used to make a l l possible comparisons within the experimental exposure period data. The significance of differences within the total data i s shown for each characteristic examined in Table VIIIA. The significance within the Individual groups was not tabulated. The between groups' significance of differences are found in Table IXA for a l l characteristics. Table XA shows the significance of interaction among egg size, fis h length, and clump size. In these latter two tables each exposure time was examined separately using Dr. N. Gilbert's computer program. Analyses of covariance were inadvisable due to unequal sample sizes. A l l tests done on hatching mortality used arcsin transformation of the percentage data. The significance of differences between beach levels for the stratification surveys are found in Table XIA. Scheffe's method was also used here. Table VIIIA: Signif icance of di f ferences wi th in the t o t a l data. C h a r a c t e r i s t i c Exposure period comparisons 0-2 2-4 4-6 6-8 0-4 2-6 4-8 0-6 2-8 0-8 (a) Incubation time •M--K- — — (b) Hatching mortal i ty^ 0 (c) Larva l length •H--H- — — (d) Larva l weight Used a r c s i n transformation. 54 Table IXA: S igni f icance of d i f ferences between groups . C h a r a c t e r i s t i c Exposure time twice per day (hr.) 0 2 4 6 8 (a) Incubation time (1) Egg s ize (2) F i s h length (3) Clump s ize — 0 — -- (b) Hatching morta l i ty (1) Egg s ize (2) F i s h length (3) Clump s ize 0 — 0 G (c) Larva l 1ength (1) Egg s ize (2) F i s h length (3) Clump s ize 0 0 (d) Larva l weight (1) Egg s ize (2) F i s h length (3) Clump s ize ** 0 * 0 Used Dr. N. G i l b e r t ' s program. Used a r c s i n transformation. 55 Table XA: S igni f icance of Interact ion- 1 . C h a r a c t e r i s t i c Exposure time twice per day (hr . ) 0 2 6 8 (a) Incubation time (1) Egg s i z e / f i s h length (2) P i sh length/clump s ize (3) Egg s ize/clump s i ze 0 0 — (b) Hatching morta l i ty^ (1) Egg s i z e / f i s h length (2) F i s h length/clump s i ze (3) Egg s ize/clump s ize 0 0 (c) L a r v a l length (1) Egg s i z e / f i s h length (2) F i s h length/clump s ize (3) Egg size/clump s i ze * — (d) L a r v a l weight (1) Egg s i z e / f i s h length (2) F i s h length/clump s ize (3) Egg s ize/clump s ize — * 1 Used Dr. N. G i l b e r t ' s program. 2 Used a r c s i n transformation. Table X I A s S igni f icance of dif ferences between beach l e v e l s . Time and place of sample Beach l e v e l comparisons B-L L-E M-H H-T B-M L - H M-T B-H L - T B-T (1) Spawning Bedwell Bay, 2 0 / 4 / 7 0 . — *# ** ## ** (2) Post-spawning (4 days) Icarus P t . , 17/3/71 . # -- — ** — 0 0 (3) Mid- incubation (8 days) Nanoose Bay, 2 7 / 3 / 7 0 . (4) Hatching (16 days) Icarus P t . , 2 9 / 3 / 7 1 . -- 0 *# — -- ON

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