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The effect of intertidal exposure on the survival and embryonic development of Pacific herring spawn Jones, Barry Cyril 1971-12-31

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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 presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the Head of my Department or by his representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of ZOOLOGY The University of British Columbia Vancouver 8, Canada November 26, 1971. ABSTRACT Eggs of Pacific herring were exposed to air for different periods of time in simulation of tidal effects 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 tide on the British Columbia coast. Egg size, spawning fish length, and egg clump size 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 thereafter fell slowly. It is suggested that oxygen deprivation triggered a hatching response for the initial drop, whereas the gradual decrease was due to a higher air temperature increasing metabolism. Hatching mortality rose steadily from an unexposed 1J% to yi% at maximum exposure time, with significantly higher contributions from eggs of smaller fish and smaller egg clumps. Larval length at hatching for the unexposed eggs was 7*7 mm.5 lengths for all degrees of exposure were similar (7% less than for no exposure). Larval weight (body plus yolk) remained relatively constant (0.099 mg.) until the longest exposure period when it dropped to O.O87 mg. This decrease coincided with similar sharp trends in incubation time and hatching mortality, and suggests a "critical point" near the upper experimental range of exposure, above which eggs stand little chance of normal development or survival. Beach surveys to note possible egg size stratification, although suggesting the deposition of larger eggs at the top levels, proved inconclusive, but point up the possibility that a heavy fishing pressure which reduces mean fish size might detrimentally affect potential stock recruitment via the intertidal exposure effect on the spawn. TABLE OF CONTENTS iii Page ABSTRACT i LIST OF TABLES iv LIST OF FIGURES v ACKNOWLEDGEMENTS • vii 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 1Incubation Time 2 Hatching Mortality 1Larval Length 5 Larval Weight 1Beach Stratification 18 DISCUSSION 1LITERATURE CITED 26 APPENDICES 9 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 list 36 IIA Incubator data list • 37 IIIA Computations for incubation time (days) ^7 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 3 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 1A Tank set-up for each exposure time 32 2A 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 6A 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  5 ACKNOWLEDGEMENTS vii I would like to thank Dr. P.A. Larkin, my supervisor, of the Department of Zoology, University of British Columbia, who gave me the opportunity, support from his National Research Council grant, and guidance in this work over the past two years. The assistance of Dr. F.H.C. Taylor and the other members of his Herring Investigation group of the Fisheries Research Board of Canada's Biological Station, Nanaimo, is also gratefully appreciated. They supplied me with the facilities, the fish, and checked, certain of my data. Thanks also go to Dr. N. Gilbert for his help in the set-up and use of his non-orthogonal analysis of variance computer program and to Dr. D.J. Randall for his helpful criticisms of the manu script. Drs. Gilbert and Randall are of the Department of Zoology, University of B.C. THE EFFECT OF INTERTIDAL EXPOSURE ON THE SURVIVAL AND EMBRYONIC DEVELOPMENT OF PACIFIC HERRING SPAWN INTRODUCTION The eggs of the Pacific herring (Clupea pallasii Val.) are spawned in and below the intertidal zone. Due to their adhesive nature, they become attached to certain forms-of seaweed and are essentially immobile. For this reason most of them are subjected to regular periods of exposure and sub mergence. Such conditions cause considerable fluctuation in the environment of the eggs and may affect their survival and development. The effect of thi>s fluctuation is ostensibly directly related to the height up the beach that the eggs are laid, and thus, the amount of time they are exposed. Within the spawning zone a variety of egg sizes can be expected because each spawner produces a range of egg sizes (for example, for Atlantic herring, Clupea harengus, Hempel and Blaxter, 1967). In addition, every reproductive stock comprises a variety of individuals differing in length, weight, and age, and several studies (Rannak, 1958; Blaxter and Hempel, 19^3) have shown that mean egg size is a function of size and maturity. The adhesiveness of herring eggs also causes the formation of clumps when exposed to sea water. Such clumps are of differing thickness and vary in egg size and number. Hence, egg size, fish size, and clump size all 2 have some bearing on the possible effects of environmental fluctuation resulting from exposure. The characteristics most notably affected are incubation time, hatching mortality, and larval length and weight at hatching. In this regard, Blaxter and Hempel (1963) noted that egg size did not affect incubation time, whereas hatching mortality was found by other studies (Runnstrom, 19^1; McMynn and Hoar, 1953) to be directly related to egg number. The larvae have been shown to be affected by both egg and fish sizes. For instance, Toom (1958) has demonstrated that larval size is directly related to egg size, and Cushing and Bridger (I966) have noted that larvae from first spawners are less viable than those from larger fish. In addition, it has also been shown (Nagasaki, 1958) that fecundity is directly related to spawner size. Because fishing intensity reduced the mean size, age, and numbers of spawners of British Columbia stocks of herring (Taylor, 1963) and North Sea herring, Clupea harengus (Cushing and Bridger, 1966), then it must follow that mean egg size also decreased. There would be fewer, smaller eggs produced than in former years, and with a lesser chance of larval survival. The survival advantage accruing to a fish stock due to the presence of larger eggs and larvae has been pointed out by Marshall (1953)- If environmental factors operating in the spawning zone are more detrimental to smaller eggs or the eggs from smaller fish, then there could be serious repercussions on recruitment potential, 3 i.e. the number of immature fish available to enter the reproductive population. Previous work on herring egg development has been concerned with conditions for submerged eggs. This study-sought to examine incubation time, hatching mortality, and larval length and weight at hatching in relation to varying degrees of exposure. The laboratory experiment was conducted and analyzed using as additional variables the effects of egg size, fish size, and clump size. A beach survey was also undertaken to note possible egg size stratification. MATERIALS AND METHODS The eggs used in this study were taken from spawning Pacific herring of the Lower East Coast stock (inner southern Vancouver Island region) of British Columbia, and the labora tory experiment was done at the Fisheries Research Board of Canada's Biological Station in Nanaimo, B.C. Spawner Characteristics Analyses Forty female spawners were used to determine if egg size was related to fish size and maturity. The first 29 were taken by beach seine and held alive in large, well-flushed holding tanks for one week prior to use. The other 11 were obtained dead from local trawlers within 6 hours of capture and used i:mmedlately. After stripping the experimental eggs, the spawners were measured for standard length (tip of snout to end of vertebral column) and three or more scales plus 4 both otoliths were taken for age determinations. The gonads were then removed and the spawner wet weight recorded. The fish were then tagged and preserved in 5$ formalin for possible future reference. The age of each spawner was determined by reading the scales from the areas above and below the lateral line between the rear of the gill cover and the front of the dorsal fin (Tester, 1937). These were cleaned, dyed, and mounted on a glass slide. The 11 trawl caught fish had very few scales, and hence, any scale was used. These ages were checked with the otoliths which had been cleaned and preserved in 5$ forma lin. Samples of each spawners' gonads were immediately pre served in S% formalin when removed. This succeeded in hardening and separating the eggs from each other and the ovarian tissue so that they could be easily counted. Sub sequently, the gonad samples were broken up to release the eggs which were then thoroughly washed in fresh water. Five samples of 100 eggs were taken from each of two fish and put in a drying oven for 24 hours at 50° Centrigrade^. Several prior tests confirmed that there were no effects of position of samples in the dryer, the dryer handling capacity, the estimation 'Of residue weight, and the length of drying time. The samples were individually removed from the oven, weighed on a Cenco electrical balance to the nearest 0.1 mg., weighed 1 These conditions 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 conditions at different beach levels (Figure 1) ranging from the control (0) which was continuously submerged, through 2, 4, 6, and 8 hours of exposure twice per day. These exposure times simulate a fixed tidal cycle of roughly 2 meters amplitude (not found in this area, but necessary as an experimental feature). Each tank contained forty incubators, and all were kept in a small temperature-controlled room under regulated conditions (Table 1). From every female spawner approximately 100 eggs were stripped into each of five separate incubators. In this operation, clumping of the eggs was unavoidable, but an <$ attempt was made to produce the same clump form in all incubators. The incubators were then simultaneously placed into a glass fertilization tray containing a sperm solution and allowed to stand for 60 seconds. The sperm solution was prepared using 500 ml. of sea water and sufficient sperm from 2 or 3 males (to ensure viable sperm) to turn the water opaque. The incubators were transferred to another tray and gently flushed with fresh sea water to prevent polyspermy and remove any excess organic matter which might decay in the tanks. They were then transferred to their respective exposure tanks and kept submerged for 12 hours before the The small size and adhesiveness of the eggs prevented counting. In fact, it was found that the mean was 132 eggs; standard deviation t kj,. 6 Exposure time twice per day (hr.) Figure 1: Relationship of beach height to exposure time. Data for Vancouver, B.C., (March, 1970) meaned from Straits Towing calendar. Table 1: Summary of experimental conditions. Factor Mean Standard Dev.(SD) (1) Light (a) (b) • • Day length Intensity 13 hours 60 watt bulb at cm. above each 75 tank — (2) Air: —Ta) (b) Temperature Relative humidity 11.7° C 65% to. 6° t5% (3) Sea Water* (a) Temperature (b) Oxygen (c) Flow rate (d) Depth 7.8° C 6.5 ml./I. 55ml. per min. per incubator 5 cm. +0.4° ±3 ml. 7 experimental conditions were initiated. The artificial environment (summarized in Table I) was similar to that recorded on the beach surveys during the experimental incubation period. An attempt was made to main tain the laboratory temperature at 12° C. A maximum-minimum thermometer checked daily gave a mean of 11.7° G; SD * 0.6°. The mean relative humidity determined by sling psychrometer was 65%', SD * 5%> The day length was regulated by time clock and set at thirteen hours (9 am to 10 pm) so that one exposure period was in the light and the other in darkness. The light source was a single 60-watt incandescent bulb per tank. Each bulb had a white porcelain rear reflector and was suspended 75 cm. above the level of the eggs in the center of the tank. The sea water originated from the bottom of the local bay and ran continuously through the tanks at a mean rate of 55 ml• per minute per incubator; SD * 3 nil. When the tanks were full, all the eggs were suspended at an equal depth of 5 cm. Several oxygen determinations were carried out on the inlet and outlet waters by the Improved Winkler Method and all came to approximately 6.5 ml. per 1. This would suggest that with plentiful oxygen in the inlet waters and the open circulatory system, oxygen was not a limiting factor-^. Regular water temperature measurements yielded a mean of 7•8° C; SD - 0.4°. This resulted in an air/water temperature differential of 4° C. 3 This was verified by a tank position analysis of the results using Dr. N. Gilbert's program. However, because the system was open and appropriate water sampling proved difficult, I would question the validity 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 fertilization to 50$ hatch) and mortality were determined. At convenient times during and after the experiment the larvae were counted and the lengths (from tip of snout to end of tail) of all 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 all put into one vial. When all 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 Distribution Beach Surveys A number of recent spawning sites were examined during daytime low tides. For purposes of comparison, the deter mination of beach height was based on the datum established by the sea level at the exact time of low tide (as indicated in the Canadian Tide and Current Tables - #5, using Point Atkinson as a reference). The sea level at this time was used as sample area M, the middle region of five beach levels sampled on each survey. The bottom sample (B) was then taken in as great a depth as practical (about 1 meter), and another sample (L-low) taken halfway between these two (about 50 cm.). The actual sample depths were determined with a graduated staff. 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 in 500 ml. jars, included as many eggs and the seaweed they adhered to as possible. Environmental conditions were also recorded at the spawning sites. Among these were the air and sea water Fixation in formalin over a three month period was shown to have negligible effects on larval weight (-0.4$) and egg weight {-0.2%) by Blaxter and Hempel (1966). Larval weight in this experiment means the total weight of the body and the yolk sac. 10 temperature, and relative humidity as determined by sling psychrometer. These data were used as a guide for the experi mental regime. Upon returning to the lab, the age of the spawn was estimated (Outram, 1955)« the samples were preserved in 5% formalin, and the beach level for each sample relative to mean low tide was calculated. Later, the eggs were separated from the seaweed by transfer to a one normal KOH solution which was then heated to 30° C. and allowed to stand for 2 hours®. The eggs and seaweed were then transferred to a 5% formalin solution again to harden for 24 hours before the seaweed was removed and discarded. This treatment not only loosened the eggs from the seaweed, but also from each other. The eggs were then thoroughly washed in fresh water, and ten 100-egg samples were taken from each beach level for drying and weighing as per the spawner egg weight determinations. RESULTS Effects of Exposure Eggs from six of the trawl caught fish had 100^ mortality in all tanks. The data from these incubators was discarded on the grounds that the eggs were probably already disintegrating 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 herring researchers at the Biological Station, Nanaimo, but slightly altered. 11 result was data from 33 spawners. On consideration, the experimental data was divided into three groups — noted as small, medium, and large .in the analyses (see Appendix D). The data were initially analysed in total to note the general trend of each characteristic in relation to increased exposure time. They were then treated separately according to their groupings as noted above. Egg size as determined from the preserved gonads was first examined for possible differences between groups. It was found of significance only in larval length and weight (see Appendix E). The second analysis examined the effects of fish length. Here hatching mortality and larval weight were shown to be affected. Since fish length and weight are so highly correlated (see Appendix C), the analysis was not repeated for weight. The effect of age was not examined as the spawners were predominantly 3-year old fish, with only a few 4 and 5-year olds. Because the egg number (clump size) was different for each incubator, a third test was run to see if this had any effect. It proved negligible for all characteristics but hatching mortality. The mean group values for these three analyses are given in Table II. Table II: Group means and standard deviations in the analyses. Grouping Small Medium Large (1) Egg size (mg.) (2) Pish length (mm.) (3) Clump Size (no.) 0.243*0. 015 199*5 89*17 0.271*0.005 211±4 130±12 0.300*0.015 223±6 175*29 12 Another analysis was performed to determine if there was any interaction among egg size, fish length, and clump size. This was found to be non-significant in most cases for all factors and hence will 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 first exposure period (2 hours) showed an abrupt decrease of close to one full day (p < .01). Thereafter, there is 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 = .01-.05). 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 fish had a higher mortality (Figure 4), but the effect was not statistically significant (p = .05-.10). Analysis of this small fish data did not indicate which egg 9 All hatching mortality statistical 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 total data. 53%T 0 2 4 6 8 Exposure time twice per day (hr.) Figure 38 Relationship of hatching mortality to exposure time for total data. 40 14 >5 •P •H H 03 P o g to •H -C o -p 03 m 30 20 10 • medium fish Figure 4: 8 ) 2 4 Exposure time twice per day (hr.) Fish length effects in the relationship between hatching mortality 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 size effects in the relationship between hatching mortality 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 initial drop between the control and the 2-hour exposure periods from 7.7 mm. to 7-2 mm. is significant (p < .01). 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 = .05-.10). 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 falling back to 0.087 mg. by the 8-hour period. None of the differences was statistically 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 = .05-.10). 8.5 16 Xi •p faO fl) I-H iH f-l 5 8.0 7.5 7.0 6.5 Figure 6: ) 2 4" 6 8 Exposure time twice per day (hr.) Relationship of larval length to exposure time for total data. xi •p bD C 0 r-n rH cd l-H 8.5 8.0 7-5 7.0 6.5 small eggs-0 Figure 7 * Exposure time twice per day (hr.) Egg size effects in the relationship between larval length and exposure time. 17 s .p s: bO •H <D DS H ts rH 0.12 0.10 0. 08 0.06 Figure 8: 0 2 4 6 8 Exposure time twice per day (hr.) Relationship of larval weight to exposure time for total data. 0.12 s 0.10 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 in the relationship between larval weight and exposure time. 8 18 Beach Stratification The beach survey done at the time of spawning (Figure 10) showed an increase in egg weight with beach height. This trend was significant (p < .01). By mid-incubation (Figure 11) the relationship had disappeared, becoming convexly curvilinear with no significant differences between beach levels. Time-sequenced observations consisting of an early (4 days) and a late (16 days - hatching) stage for a single egg mass was done to clarify this problem (Figure 12). However, the l6-day sample was taken lower down on the beach and hatched en route to the laboratory. The larval weights obtained were assumed to be a reflection of their former egg weights and were com pared with the k— day sample on a relative basis. No significant trends were indicated. DISCUSSION The spawners used in this experiment were essentially all recently mature herring. As such, the results found are only truly applicable to the spawn of these young fish. The exposure time imposed on the spawn ranged up to 2/3 of a day, and reduced incubation time, increased hatching mortality, and reduced larval length and weight. Possible explanations for some of these patterns are presented below. Incubation time dropped markedly when the eggs were first exposed, but thereafter decreased gradually with increased exposure time. The drop with only two 2-hour exposure periods per day may be due to oxygen deprivation. In this regard, 19 0.24h 0.22 bD -p W 0.20 0) bO bO W 0.18 MLT 0 3.0 1.0 2.0 Beach Height (m.) Figure 10: Relationship of egg size to beach height at spawning, Bedwell Bay, April 20, 1970. 0.24 r 0.22 b0 6 p bo 0.20 •H CD bD bO 0.18 M MLT 0 1.0 2.0 Beach Height (m.) 3-0 Figure 11: Relationship of egg size to beach height at mid-incubation (8 days), Nanoose Bay, March 27, 1970. 20 0.28 0.26 | 0.24 b0 w 0.22 0.20 0.14 0.12 0.10 (4 days) (16 days) MLT -1.0 1.0 Beach Height (m.) 2.0 Figure 12 Relationship of egg size to beach height just after spawning (4 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. 21 Volodin (1956) noted that there was an erratic but twofold increase in oxygen requirements over the incubation period. In addition, Rannak (1958) found that hatching was initiated when eggs were transferred to lower oxygen pressures. Thus, whereas oxygen needs were satisfied in air and water when the embryos began development, just prior to hatching, when oxygen demand was much higher, the eggs may have been incapable of obtaining adequate supplies from air. A possible reason for lower oxygen availability in air would be the impairment of the egg membrane by desiccation, thereby restricting entry. As no larvae hatched out during the exposure periods, it might be that a more flaccid nature of the membrane due to desiccation prevented its rupturing until the eggs were once more submerged and their membranes taut by internal pressure. In this study, the beach survey eggs collected at 16 days were inadvertently made to hatch en route to the laboratory. As considerable living organic matter was enclosed in a very small space, the oxygen was undoubtedly depleted in a very short time, and hence, could have initiated hatching of the eggs. The overall gradual decrease in incubation time is likely due to the higher temperature encountered in the air, promoting an increased metabolic rate. For the highest degree of exposure examined, the incubation time reached a minimum of 17.8 days. The reduction in time at this beach level was roughly 7%, over 5$ of which is accounted for by the first exposure drop. This phenomenon provides a possible reason for deposition of spawn in the intertidal zone, which obviously must be of some advantage to the species survival, and that is to attune hatching to 22 increased air and surface water temperatures which are associated with plankton production, the source of larval sustenance. In other words, as plankton production is dependent on temperature, so also is incubation time of herring spawn (Blaxter and Hempel, I966), and their coincidence would naturally be beneficial to the emerging larvae. 'Unfortunately, exposure of spawn also has several dis advantages. Among these are the increased hatching mortality and detrimental effects on larval length and weight. The hatching mortality on the spawning grounds was con sidered by Taylor (1964) to average 37$ if losses due to bird predation were not included. This may be attributed to inviability, overcrowding, and exposure to wave action and desiccation. The results of this experiment show a mortality somewhat lower than this (13 to 31%), and being dependent upon the duration of exposure. To some degree, wave action which was not an experimental feature could account for the difference. What part inviability of eggs played cannot be deduced in this study. Eggs from small fish had a higher mortality than those from larger spawners. Toom (1958) has demonstrated that less viable larvae are produced by small fish, and hence, one might suspect that they were incapable of surviving the rigors of exposure or completing hatching manipulations. The egg density seems to have mixed effects. On the one hand large clumps might hinder fertilization, limit oxygen supplies, and promote waste product accumulation of the internal eggs. On the other hand, these same larger 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 will 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 will 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 will 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 distribution is in fact borne out by Taylor (1964) and the beach samples taken in this study. It might even occur that an exceptionally high tide during a spawning would result in eggs being deposited too high on the beach and hence, sub jecting them to a much more severe degree of mortality. This could account for some part of year-class fluctuation in numbers. On the other hand, laying eggs high on the beach has been shown (Tester, 1942) to contribute to year-class survival. In this case, the eggs on the lower beach and in the water died for some unknown reason, while the higher eggs survived. As already suggested, exposure also has some effects on larval characteristics., The initial drop in larval length (7%) at first exposure is expected, as earlier hatching would certainly mean less time for larval growth or the conversion of yolk into body tissue. The lack of further decrease with additional exposure might well be due to the increasing mean temperature enhancing the metabolic rate and hence, nullifying incubation time differences. Alternatively, these results may verify Hamdorf's (I96I) view that larval length is directly related to the prevailing oxygen pressure and is independent of exposure time. To some degree earlier hatching must also add to mortality during the larval stage if, as Rannak (I958) has stated, exposure prior to hatching readiness results in premature and therefore less viable larvae. This experiment indicated that the smaller eggs yielded shorter larvae. It might be that these larvae are less viable 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 initial 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 utilization 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 "critical point" in exposure time is reached above which the environment is so harsh that the eggs stand little 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 fitted to survive. In consequence, reduction in the 26 size of spawning fish implies a lower average rate of survival. An optimum clump size is further suggested, but its relationship to fish size or beach level is unknown. Though the older and larger fish spawn first (Rannak, 1958), since the spawning period usually lasts several days (and therefore twice as many tidal movements), the eggs of all fish may be evenly distri buted over the spawning zone. The beach collection of eggs at spawning did however indicate that the larger eggs were further up the beach. Unfortunately, the other beach surveys were far less instructive, and the trends are further complicated by the increasing mortality with exposure and the differential mortality due to fish and clump sizes. Another source of confusion is the possible effects of wave action and predation by birds as noted earlier. In any event, a heavy fishing intensity which kept the individual fish size small would imply a decreased average rate of survival at higher levels of spawning. Thus, fishing pressure has a hidden dimension in also reducing spawn survival. LITERATURE CITED Blaxter, J.H.S., and G. Hempel (I96D "Biologische Beobachtungen bei der Aufzucht von Heringsbrut", Helgoland. Wiss. Meeresunters., 7(5): 260-283. (Fish. Res. Bd. Canada, English translation #708) Blaxter, J.H.S., and G. Hempel (1963) "The influence of egg size on herring larvae (Clupea harengus L.)", J. Cons. Expl. Mer, 28(2): 211-2-4-0. 27 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. 25(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., 44(5): 523-549. Hempel, G., and J.H.S. Blaxter (I967) "Egg weight in Atlantic herring (Clupea harengus L.)", J. Cons. Expl. Mer, 31(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 investigations on herring spawning and its yearly fluctuations at the west coast of Norway", Flskeridir. Skr. Havundrsok., 6(7 ): 71 PP« Taylor, F.H.C. (I963) "The stock-recruitment relationship in British Columbia herring populations", Rapp. C.P.I.E.M., 15^1 279-292. Taylor, F.H.C. (1964) Life History and Present Status of British Columbia  Herring Stocks. Fish. Res. Bd. Canada, Bulletin #143, 81 pp. Tester, A.L. (1937) "Populations of herring (Clupea pallasii) in the coastal waters of British Columbia", J. Fish. Res. Bd. Canada, 3(2): 108-144. Tester, A.L. (1942) "A high mortality of herring eggs", Fish. Res. Bd. Canada, Prog. Rep. Pac., 53* 16-19. Toom, M.M. (1958) — in Russian. ("Experiments in the incubation of Baltic herring eggs"), Trudy VNIRO, 34: 19-29-(Office of Tech. Serv., U.S. Dept. of Commerce, Wash. 25, D.C., USA, English translation #6ll) Volodin, V.M. (1956) — in Russian. ("Embryonic development of the autumn Baltic herring and their oxygen requirements during the course of development"), Voprosy Ikhtiologll, 7- 123-133-(Fish. Res. Bd. Canada, English translation #252) 29 APPENDICES 30 APPENDIX A - Apparatus Design The tank, fittings, and tubing were all polyethylene. For each tank, the water inflow divided into four separate compartments of ten incubators entering at the bottom rear (Figure 1A). During the exposure period it flowed across the floor under the incubators and out the bottom front control drain, exiting through the electrical valve. This valve was open only when:., energized and operated on a time clock. During submergence the valve was closed and the water filled the tank, flowing out the top front overflow. Emptying or filling the tank took J or k minutes. The incubators (Figure 2A) were made from 3 mm. plexi glass tubing (2.5 cm. inside diameter) open at the top. The bottom and the four mid-level side ports (1.25 cm. diameter) were covered with Nitex #253 monofilament nylon screen. The lower 1.25 cm. separated from the top which it secured with a tight friction-grip band. The reason for this was to allow easy stripping of the eggs onto the bottom screen. This whole unit was bonded together using ethylene dichloride. Each tank compartment was divided in half horizontally by a plexiglass plate (secured by Silicone Sealant) through which ten holes had been drilled. The incubators fitted through these holes and locked in by bayonet mount so the changing water level did not dislodge them. The water was made to flow up through the eggs and out the side ports when submerged, never reaching the top of the tube. Due to their 31 demersal and adhesive nature, the eggs themselves remained attached to the bottom screen and did not float freely in the upper tube. The apparatus was run continuously for two weeks prior to the experiment - for adjustment of the environmental conditions and the removal of possible leaching material which might affect the eggs. Figure 2A: Cross-section of incubator in tank. 33 APPENDIX B - Raw Data The data for the spawners (Table IA) is listed according to the fish number, the order in which they were used. Numbers 14, 30 to 34, and 39 were eliminated due to 100$ mortality in all incubators. Why the eggs from spawner #14 died is not known. On examination they formed a hard mass with no sign of embryonic development. It is possible they may have been infertile or were in the process of being reabsorbed when stripped. The latter is said to happen when spawners are kept for long periods in holding tanks. The other six fish were from the trawl caught batch, and all the eggs disintegrated. So as not to affect the other healthy eggs, these incubators were all removed halfway through the incubation period. Data for a total of 33 female spawners was left for analysis. Table IIA lists the individual incubator data by ex posure index. The Incubator number consists of the fish 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 sentinels only. This lack of data is based on the following criteria: (a) Incubation time - if less than 20 eggs hatched, the distribution seemed too disperse to pinpoint 50$ hatch. Pour values were rejected on this basis. (b) Hatching mortality - any incubator with an egg number less than 45 was considered inadequate for comparison 3k with means based on more eggs. This level is 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 electri cal balance was the deciding factor here. Thus, anything less than 15 larvae was determined inadequate to yield a fair 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. Oi 2738 25 219. 107. 3. 0.3204 Zb 2U /. 8 / • ii. 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 19. . 15 13. .3 7, .3 1 0.000 255 . 20 19* • 18 12 . 11 7. .20 0. 000 132* 30 18. .82 3. .6 7. 44 0.066 166. 40 19. >Q5 5. 9 7. .36 0.056 102. 50 19. .76 14. .5 7. .17 0.068 166 e 60 19. .07 12. 3 6. .91 0.050 65 . 70 19. .36 17. .4 7. .22 0.084 92. 80 19 • 22 19. 0 7. .35 0.083 79. 90 18. .71 1. .8 7« .11 0.066 112. 100 19. i04 16. »1 6. .89 0.117 56. 110 18 • 70 3 . . 2 7. .15 0.076 216. 12U IB • 62 19. . 3 (i .19 0.081 ii?U . 130 18. .95 16. .2 7. .30 0.085 136. 150 19. . 19 42. .4 7. .38 0*092 118 . 160 20. .15 23. .7 7. .7 5 0.087 156. 170 19. .05 26. ,0 6. 80 0.074 104. 180 18. .48 13. .6 7. .98 0. 105 81. 190 19. .12 0. . / / .B5 0.082 142 . 200 18. .91 3. .6 7. 90 0.098 138 . 2 10 19 .32 6. .5 8. .40 0.099 107. 220 18 .66 10. . 3 7. .85 0.093 126. 230 19 .59 13. .4 8. .2 1 0. 109 97. 24 0 18. .75 6. .5 7. 99 0.102 155. 18 .64 3 . 6 8 .49 0. 123 111. 260 18 i76 4 .3 8 .33 0. 106 185. 270 18 .79 6 .3 8. .2 2 0.121 144. 280 19 .72 7 .2 8. .15 0.113 166. 290 19 .91 7 .3 8 .27 0.108 193. 350 19 .50 17 .4 8 .28 0.114 121. 36U 19 .5 3 IV . 2 8 .8 2 0.12/ . ftit 370 19 .83 2 1. .7 8 .19 0. 120 106. 380 19 .50 26. .9 8. .28 0.088 167. 400 19 » 15 14. .6 7, .96 0.072 89 . TABLE I IA (CONTINUED) 38 2 HOUR DATA INCUBATOR INCUBATION HATCHING LARVAL LARVAL NUMBER NUMBER TIME MORTALITY LENGTH WEIGHT OF (DAYS) I PER CENT) (MM.) (MG.) EGGS 12 18. .00 29. .2 7< .07 0. 054 250. 22 18i .30 19. . 1 It 07 0* 104 157. 32 18. .25 18. .2 6< 89 0.076 137« 42 18. .33 5 < 1 6« 92 0.089 156. 52 18. .33 26. 7 6. .64 0.090 131. 62 18. .29 3 < .1 6. 96 0.080 98. 72 18. .28 20. .5 It 06 0. 100 127. 82 18. .38 18. .3 6. .79 0.080 131. 92 18. .04 4i 0 6. .87 0.070 101. 102 18. . 13 8« 5 6. .74 0. 107 142. 112 18. . 14 1. .8 6« 89 0.103 170. 122 18. .34 36. .4 6. .51 0.081 154. 132 18. .06 44. .3 6. .45 0.083 79. 152 0. .00 76. > 1 0< .00 0.000 46. 162 18. .20 31. .9 6. .50 0.090 94. 172 18. . 10 21. 0 6< .33 0.079 143. 182 17. .61 3. ,7 6. 90 0.098 81. 192 18. .00 4. .8 6. .68 0.084 147. 202 18. .86 8. .3 7. .93 0.120 156. 212 18. .04 7. .5 6. .69 0.097 93. 222 17. .99 2. 7 6. .82 0.085 110. 232 18. .26 13. 7 7. .11 0. 102 95. 242 18. .08 13. 9 6. .72 0.098 101. 252 17. .46 18. .3 7. .5 1 0.122 131 e 262 17 .57 1. .4 7. .98 0.131 145. 272 17 .85 10. .1 7. .92 0.151 148 . 282 17. .74 0. .6 8< .00 0.109 168. 292 18 .53 5. 9 8 .06 0.101 271. 352 18. .25 10. .4 8. .07 0.114 173. 362 18 .50 54. .5 8. .03 0.131 101. 372 18 .51 16. .8 8 .09 0.120 113. 382 18. .57 15. .4 7, . 89 0.086 247. 402 18 .47 34. .3 8 .14 0.067 67. TABLE I IA (CONTINUED) 39 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. T7^+ 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. TABLE I IA (CONTINUED) 40 6 HOUR DATA INCUBATOR INCUBATION HATCHING LARVAL LARVAL NUMBER NUMBER TIME MORTALITY LENGTH WEIGHT OF (DAYS) (PER CENT) (MM.) (MG.) EGGS 16 17. .93 35. .7 6. 94 0.063 140. 26 18 .44 3. 0 7. .02 0.106 199 . 36 17 .96 14. .5 6< .75 0.069 131. -+6 18 .27 12. .5 6. .54 0.076 128. 56 18 .21 40. 0 6. .35 0.112 85. 66 18 .31 10. .9 6. .66 0.082 129. 76 18 118 11. .2 6. .74 0.090 116. 86 18 .02 16. 9 6. 87 0.076 148 . 96 18. .06 11. . 1 6< 40 0.088 117. 106 18. .24 14. .4 7. .12 0.127 97. 116 18. .66 34< 7 6. .49 0.073 118 a 126 18 .36 20. 2 6. 64 0.090 130. 136 18. .02 74. .2 Oi 00 0.000 89 . 156 18 .25 73. 0 0. .00 0.000 111. 166 18. .79 39. 8 7« 06 0. 102 12 3. 176 18 .48 10i .2 6. .52 0.070 157. 186 17. .98 8. 8 7« .34 0.124 80 . 196 17. .96 6. .6 6. .91 0.089 152. 206 18. .52 24. 7 7. 01 0. 104 170 . 216 18. .39 40. 0 7. .43 0. 106 130. 226 16. .76 10. 9 7. .33 0.088 17 5. 236 18. .61 37. .3 7. 87 0.118 150. 246 18. .54 20. 0 7. .57 0.114 180 . 256 17. .82 6. .3 7. 89 0.121 159 . 266 17. .69 2. .4 7. 79 0. 10 7 167. 276 17. .66 1. .3 7« 87 0.125 152. 286 17. .92 13. 9 8. 05 0. 146 187. 29 6 17 • 81 2. .4 8. .10 0.110 167. 356 17 .69 13. . 1 8. .07 0.113 145 . 366 18 • 63 53. . 1 0< .00 0. 108 81. 376 17 • 64 26. .8 8. .08 0.117 112. 386 16 • 76 25« 9 7. .60 0.087 135. 40 6 17 • 64 49. .5 7 .48 0.077 107. TABLE I IA (CONTINUED) 4l 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 Oi ,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 Oi , 102 118 . 198 17 . .58 3 i . . V bi .84 UI >UtiU iy 2 . 20 8 17. .57 36 . .5 6. .95 Oi ,072 178. 218 0 .00 73. .7 0, 00 OI ,000 57. 228 18. .27 14. .2 6, .76 Oi ,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 li .49 0< » 102 226. 278 17 .68 26 .3 li ,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 Correlations 42 A comparison of the various experimental spawner characteristics led to the following observations: The egg size was found to be weakly correlated to fish length (Figure 3A), fish weight (Figure 4A), and to fish age (Figure 5A). On the other hand, fish length (Figure 6k) and fish weight (Figure ?A) were more strongly related to fish age, and the relationship of fish length to fish weight (Figure 8A) was very highly correlated. From this information, it was decided that egg size and fish length would be used as bases for analyzing the incubator data. The use of both fish weight and length would have been redundant due to their high association. Length was selected as these measurements were more exact; weight involved possible variation in moisture content and vestiges of gonads (which were removed for this determination since indeterminable amounts of eggs were already missing). The use of age was rejected because of the very narrow and skewed distribution of values. In addition, due to the poor correlation of fish length and egg size, it 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 ' 200 ' 210 ' 220 ' 230 Spawner Length (mm.) Figure 3A» Relationship of egg size 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— ^60 80 100 120 Spawner Weight (gm.) Figure 4A: Relationship of egg size to spawner weight with gonads removed. 140 0.32 0.30 g> 0.28 -p «> 0.26 'H <D bO M 0.24 0.22 o o 3 44 Spawner Age (yr.) Figure 5A: Relationship of egg size to spawner age. 240 r Spawner Age (yr. ) Figure 6As Relationship of spawner length to age. 140 Spawner Age (yr.) Figure 7A: Relationship of spawner weight with gonads removed to age. 46 APPENDIX D - Computations Summary These tables summarize the means and standard deviations of all the analyses made in this study. For the experimental work, there is 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 criteria laid out in Appendix B. Maximally, it should be 33 for the total data and 11 each for the groupings. In fact, it is 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 is 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 for incubation time (days). Exposure time twice per day (hr. ) Characteristic 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 for 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 size 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) Fish 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 larval length (mm.). Exposure time twice per day (hr.) Characteristic 0 2 4 6 8 (1) Total data 7.72 0.55 7.19 + 0.60 7.13 + 0.34 7.22 ± 0.57 7.12 ± 0.52 (2) Egg size 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) Fish 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 size 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 larval weight (mg.). Exposure time twice per day (hr.) Characteristic 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 size 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) Fish 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 size 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 stratification 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 arbitrarily set at forty (with five exposure periods) so that, with possible rejections, a good range of differences in egg and fish 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 all possible comparisons within the experimental exposure period data. The significance of differences within the total data is 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 all characteristics. Table XA shows the significance of interaction among egg size, fish 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. All 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: Significance of differences within the total data. Characteristic 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 mortality^ 0 (c) Larval length •H--H- — — (d) Larval weight Used arcsin transformation. 54 Table IXA: Significance of differences between groups . Characteristic Exposure time twice per day (hr.) 0 2 4 6 8 (a) Incubation time (1) Egg size (2) Fish length (3) Clump size — 0 — --(b) Hatching mortality (1) Egg size (2) Fish length (3) Clump size 0 — 0 G (c) Larval 1ength (1) Egg size (2) Fish length (3) Clump size 0 0 (d) Larval weight (1) Egg size (2) Fish length (3) Clump size ** 0 * 0 Used Dr. N. Gilbert's program. Used arcsin transformation. 55 Table XA: Significance of Interaction-1. Characteristic Exposure time twice per day (hr.) 0 2 6 8 (a) Incubation time (1) Egg size/fish length (2) Pish length/clump size (3) Egg size/clump size 0 0 — (b) Hatching mortality^ (1) Egg size/fish length (2) Fish length/clump size (3) Egg size/clump size 0 0 (c) Larval length (1) Egg size/fish length (2) Fish length/clump size (3) Egg size/clump size * — (d) Larval weight (1) Egg size/fish length (2) Fish length/clump size (3) Egg size/clump size — * 1 Used Dr. N. Gilbert's program. 2 Used arcsin transformation. Table XIAs Significance of differences between beach levels. Time and place of sample Beach level 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, 20/4/70. — *# ** ## ** (2) Post-spawning (4 days) Icarus Pt., 17/3/71. # -- — ** — 0 0 (3) Mid-incubation (8 days) Nanoose Bay, 27/3/70. (4) Hatching (16 days) Icarus Pt., 29/3/71. -- 0 *# — --ON 

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