A computer simulation model was written to mimic the natural movement of salmon fry in Babine Lake, B.C.. Simulated distributions of fry were compared with field observations taken in 3 sampling periods during the summer and fall in 1967, 1968, 1971, and 1972, in order to evaluate the model's validity. Simulated distributions of fry, when random and heavily-biased movements were combined, were in reasonable accord with naturally observed distributions of fry in periods 1 and 2. In period 3 the model successfully produced a distribution similar to that naturally observed when the fry were programmed to undergo only random movement. Factors which might account for the various distributions of fry in different periods include the effects of current and innate behavioral responses of the fry to limnological conditions. In constructing my model, I assumed that fry travelled at speeds observed in the laboratory in still water. The model of fry dispersal in Babine Lake could be improved as more information is collected on the limnology of the lake and on fry behavior. In addition, the model has much generality and the techniques used may be applied to the dispersal of other organisms and to other lakes. / Science, Faculty of / Zoology, Department of / Graduate

A procedure for applying the concepts of Bayesian decision theory to salmon management is presented and illustrated with an application to the Babine system sockeye salmon fishery in British Columbia. The particular decision considered is the recommended escapement to aim for in a given year. The Babine fishery is described and the decision theory concepts are outlined. The procedure involves defining the relationship between the recommended spawning escapement and the number of adults returning in the cycle year in probabilistic terms; defining the utility, that is the relative desirability of various sizes of catch; and computing the total expected utility of both the catch in the current year and the spawning returns associated with alternative values of the recommended escapement. The escapement with the maximum expected utility should be chosen and recommended. / Graduate and Postdoctoral Studies / Graduate

Various aspects of downstream migratory behavior of sockeye salmon fry (pncorhynchus nerka) were examined in a series of field and laboratory experiments. The field work at the Department of tie Environment (Fisheries and Marine Service) Fulton Eiver spawning channels, Babine Lake, British Columbia, was concerned with the predation by rainbow trout (Salmo gairdneri) and whitefish (Prosopium williamsoni) on sockeye fry with various kinds of prior experience. The laboratory studies focused on the effects of exposure to light on the behavior of emerging and recently emerged fry. The results showed that : (1) the number of fry moving downstream varies throughout the nightly migration period; (2) the presence cf predators modifies the movement pattern of migrating fry, such that the fry tend to move downstream over a more concentrated time period; (3) fry response to predators tends not to be predator-specific, migrating fry respond similarly to different species of predators; (4) emergent fry are not all similar in their migratory behavior, some tend to migrate rapidly (fast migrants), while others migrate at a slower rate (slow migrants); (5) generally fry with prior experience to predators displayed different migratory behavior compared to fast and slow migrants; and (6) subjecting newly-emerged fry to increasing time periods of light treatment and fry densities, alters behavior patterns. It is concluded that fry commencing downstream movement are not all similar in their migratory behavior. Begardless of the basis for the behavioral difference between fast and slow migrants, the presence of predators modifies and enhances downstream movement. Further, subjecting premigratory fry to light, alters downstream movement and behavioral interactions between fry. / Science, Faculty of / Zoology, Department of / Unknown

The question to which this study is addressed is: can the Eraser River sockeye salmon fishery be managed in such a way as to maximize its present worth? A review of the existing biological and economics literature would suggest that such optimal management is indeed possible. Putting numbers into the theoretical equations and solving for an optimal solution has been based on a three part approach. First, a Ricker form of recruitment function was used to model the basic interseasonal relationship between spawning escapement and subsequent future recruitment. Second, nonlinear production functions were used to model the harvesting process in a highly cyclical fishery spread out over a fairly extensive fishing gauntlet. And third, it is assumed that the manager is faced with two inter-related problems which must be solved simultaneously: he must decide the optimal escapement which has future revenue consequences in terms of size of catch and future cost consequences in terms of size of the subsequent recruitment (the larger the recruitment, the lower the harvesting costs), and he must decide the least cost spatial combination of harvesting gear to take the specified catch. The major finding of this study is that it is possible to manage the Fraser River sockeye salmon fishery in an optimal manner and to do so would increase its present worth substantially. The use of cycle dummy variables to allow for the marked four year cycles in both recruitment and harvesting patterns plays a major role in improving parameter estimation. Nonlinear programming techniques can be developed to allow the simultaneous determination of the optimal intertemporal spawning escapement and the least cost spatial allocation of effort to harvest the optimal catch. The original contribution of this dissertation lies in its use of deterministic models to empirically solve the problem of optimal management of a fishery. / Arts, Faculty of / Vancouver School of Economics / Graduate

This study reports the occurrence of daily rings in the otoliths of Oncorhynchus nerka fry and examines their relationship to growth. In experiment 1, sockeye salmon fry were collected from the Fulton River spawning channel at Babine Lake, British Columbia in May 1978. The fish were reared for 26 days in enclosures in the spawning channel and were sampled every seven to ten days. Sagittae were removed from 25 fish from each sample, and the growth rings in one otolith from each fish were counted. A regression of the number of rings on the number of days since capture showed that these rings are, on average, formed daily, beginning at the time of emergence. A number of possible technical and biological causes of variation in ring counts within and between samples are considered. In Experiment 2, sockeye salmon fry were reared in the laboratory from fertilized eggs taken in the fall of 1978 at the Weaver Creek spawning channel near Mission, British Columbia. A random sample of 64 of these fry was marked to enable identification of individuals. Each individual was weighed initially on June 6 or 8, again on July 6, and surviving fish were weighed a third time on July 20. After a final weighing, sagittae were removed and a standard otolith radius was determined by counting back the appropriate number of daily rings which corresponded to each weight. The regression of £n otolith radius on £n fish weight was linear, and had an R2 of 0.92, which demonstrates a relationship between the mean width of a daily ring in sockeye salmon fry sagittae, and a mean daily change in the weight of the fry. Using this regression line, we back-calculated the previous weight of the individual fish from the corresponding otolith radius and a latter fish weight and otolith radius and found the errors to be relatively small — in the order of 15 per cent. / Science, Faculty of / Zoology, Department of / Graduate

Migration timing is a conserved life-history trait. To address the hypothesis that reproductive hormones are principal determinants of migration timing, I physiologically biopsied over 1000 sockeye salmon and monitored their subsequent behaviour with acoustic and radio telemetry as they migrated from the Pacific Ocean toward and into the Fraser River, and then onward to distant spawning areas. Links between physiology, behaviour, and survival were examined. Circulating testosterone was found to be positively correlated with the rates of river entry in Late-run females but not in males, despite having concentrations that were equal if not higher than those of females. The notion of protandrous migration, in which males synchronize their activities to the reproductive and migratory schedules of females, was postulated as the basis for this difference. Once in river however, successful males and females were those that (1) took longest to enter the river, and (2) had high somatic energy, low testosterone, and low gill Na+,K+-ATPase activities. An experimental test of the effect of reproductive hormones on the regulation of migration timing proved inconclusive. Relative to controls, GnRH and (or) testosterone treatment did not influence rates of ocean travel by males. Unfortunately, no females were examined. Nevertheless, significant, positive correlations between initial testosterone and travel times were found irrespective of hormonal treatment, which was unexpected but consistent with the previous studies. In an experimental simulation of an ‘early’ migration, normally timed Late-run sockeye exposed to typical 10 ºC river temperatures and then released to complete migration were 68% successful. In contrast, salmon held at 18 °C and released were half as successful. The expression of a kidney parasite was near maximal in the 18 °C fish and undetectable in the 10 °C fish. Only gill Na+,K+-ATPase activity differed between groups, with a drop in the 18 °C fish. Though no clear stress, reproductive, or energetic differences were observed between groups, the ultimate effect of high temperature treatment was high disease expression, slowed migration speeds, and high migration mortality. Changes in reproductive schedules, due to changes in latitudinal ocean distributions, are discussed as potential causes of early migration by Late-run sockeye.

Migration timing is a conserved life-history trait. To address the hypothesis that reproductive hormones are principal determinants of migration timing, I physiologically biopsied over 1000 sockeye salmon and monitored their subsequent behaviour with acoustic and radio telemetry as they migrated from the Pacific Ocean toward and into the Fraser River, and then onward to distant spawning areas. Links between physiology, behaviour, and survival were examined. Circulating testosterone was found to be positively correlated with the rates of river entry in Late-run females but not in males, despite having concentrations that were equal if not higher than those of females. The notion of protandrous migration, in which males synchronize their activities to the reproductive and migratory schedules of females, was postulated as the basis for this difference. Once in river however, successful males and females were those that (1) took longest to enter the river, and (2) had high somatic energy, low testosterone, and low gill Na+,K+-ATPase activities. An experimental test of the effect of reproductive hormones on the regulation of migration timing proved inconclusive. Relative to controls, GnRH and (or) testosterone treatment did not influence rates of ocean travel by males. Unfortunately, no females were examined. Nevertheless, significant, positive correlations between initial testosterone and travel times were found irrespective of hormonal treatment, which was unexpected but consistent with the previous studies. In an experimental simulation of an ‘early’ migration, normally timed Late-run sockeye exposed to typical 10 ºC river temperatures and then released to complete migration were 68% successful. In contrast, salmon held at 18 °C and released were half as successful. The expression of a kidney parasite was near maximal in the 18 °C fish and undetectable in the 10 °C fish. Only gill Na+,K+-ATPase activity differed between groups, with a drop in the 18 °C fish. Though no clear stress, reproductive, or energetic differences were observed between groups, the ultimate effect of high temperature treatment was high disease expression, slowed migration speeds, and high migration mortality. Changes in reproductive schedules, due to changes in latitudinal ocean distributions, are discussed as potential causes of early migration by Late-run sockeye.

Animal migrations are often associated with high mortality due to increased energy expenditure, reduced foraging opportunities, and increased predation risk. Migratory traits such as body size, phenology, or use of stopover habitats may moderate individual risk to mortality mechanisms and influence patterns of survival. However, variability in migratory traits is rarely quantified in detail because tracking many individuals over large areas is logistically challenging. In this dissertation, I used otoliths to examine migratory variability among and within sockeye salmon (Oncorhynchus nerka) populations, a species that has recently experienced declines associated with poor survival during juvenile marine migrations. Broadly, I examined the individual and environmental drivers of migratory patterns, as well as how variation across ecological scales (individuals, populations, and years) contributed to migratory diversity. First, I conducted a laboratory study to validate the use of otolith microstructure techniques in sockeye salmon post-smolts. Next, I assessed how a suite of ecological processes could interact to create a latitudinal gradient in sockeye salmon body size. By reconstructing individual growth and migration histories I determined that variation in size was correlated with ocean entry size and phenology, rather than differential marine growth or size-selective mortality. I then used estimates of migratory rate from otoliths to demonstrate that juvenile sockeye salmon exhibited distinct migratory phenotypes associated with ocean entry traits. Larger individuals migrated rapidly offshore, while smaller fish reared for several weeks in nearshore regions. Furthermore, a subset of the smallest individuals entered the ocean late in the year, migrated particularly slowly, and may have overwintered on the continental shelf. These linkages between ocean entry and migratory traits suggest juvenile sockeye salmon exhibit substantial migratory plasticity associated with carry-over effects from freshwater residence; however juvenile salmon may also respond strongly to variable conditions in marine habitats. In my fifth chapter, I compared marine growth and migration phenology in years with low and high competitor densities. After accounting for freshwater density-dependent effects, growth rates were similar in both years, but mean migration rates were nearly 50% faster in the high-density year. Migratory behavior may be used to buffer individuals from the effect of competitive interactions. In my final chapter, I sampled 16 Fraser River sockeye salmon populations to explore variation in the timing and duration of early marine migrations. Although populations differed in downstream migration timing, as well as their duration of residence within nearshore habitats, there was substantial variation within each population and between sampling years. These findings suggest individual characteristics and stochastic processes interact with population-specific strategies to shape migratory phenologies in this metapopulation. Management actions should account for and preserve migratory diversity at multiple ecological scales to maintain resilient salmon populations into the future. / Graduate / 2018-10-17

Migration timing is a conserved life-history trait. To address the hypothesis that reproductive hormones are principal determinants of migration timing, I physiologically biopsied over 1000 sockeye salmon and monitored their subsequent behaviour with acoustic and radio telemetry as they migrated from the Pacific Ocean toward and into the Fraser River, and then onward to distant spawning areas. Links between physiology, behaviour, and survival were examined. Circulating testosterone was found to be positively correlated with the rates of river entry in Late-run females but not in males, despite having concentrations that were equal if not higher than those of females. The notion of protandrous migration, in which males synchronize their activities to the reproductive and migratory schedules of females, was postulated as the basis for this difference. Once in river however, successful males and females were those that (1) took longest to enter the river, and (2) had high somatic energy, low testosterone, and low gill Na+,K+-ATPase activities. An experimental test of the effect of reproductive hormones on the regulation of migration timing proved inconclusive. Relative to controls, GnRH and (or) testosterone treatment did not influence rates of ocean travel by males. Unfortunately, no females were examined. Nevertheless, significant, positive correlations between initial testosterone and travel times were found irrespective of hormonal treatment, which was unexpected but consistent with the previous studies. In an experimental simulation of an ‘early’ migration, normally timed Late-run sockeye exposed to typical 10 ºC river temperatures and then released to complete migration were 68% successful. In contrast, salmon held at 18 °C and released were half as successful. The expression of a kidney parasite was near maximal in the 18 °C fish and undetectable in the 10 °C fish. Only gill Na+,K+-ATPase activity differed between groups, with a drop in the 18 °C fish. Though no clear stress, reproductive, or energetic differences were observed between groups, the ultimate effect of high temperature treatment was high disease expression, slowed migration speeds, and high migration mortality. Changes in reproductive schedules, due to changes in latitudinal ocean distributions, are discussed as potential causes of early migration by Late-run sockeye. / Forestry, Faculty of / Graduate

The genetic relationship of anadromous (sockeye salmon) and non-anadromous (kokanee) Oncorhynchus nerka was examined in conjunction with the breeding behaviour of the two forms to determine: (1) if there is evidence of genetic divergence between the forms where they spawn sympatrically; (2) if such divergence is associated with significant premating isolation between the forms and; (3) if premating isolation results directly from the size difference between the forms (sockeye are much larger than kokanee at maturity). Both sexes exhibit spawning territoriality; females establish and defend particular nest sites until death or displacement, males defend access to specific females from other males until the female has spawned out, they are displaced, or leave to compete for additional mates. Size and prior access to resources (mates and/or specific areas) are significant factors in intrasexual aggression in both sexes, with size the major factor in males and prior access the major factor in females. Females accompanied by males larger than themselves lose weight at a faster rate than those accompanied by males smaller than themselves. Weight loss is related to egg loss, indicating females spawn at a faster rate when accompanied by large males. Male mate preference depends on the size of the male. Males of various sizes prefer females of their own size or larger over females smaller than themselves. In contrast, all sizes of males tested demonstrated no preference between females of their own size and those larger. Large males, which have the widest range of potential mates (because of male intrasexual competition and female choice), are the most selective and small males, which have the narrowest range of potential mates, are the least selective. There were significant differences in allele frequencies between sympatrically spawning sockeye and kokanee. However, there were no consistent differences between sockeye and kokanee at any of five polymorphic loci examined. The extent of genetic differentiation between sympatric forms appears to be less than that between neighbouring populations of the same form, judging from an examination of allele frequencies and/or allele compositions. There was extensive assortative mating by form between sockeye and kokanee, which was not totally accounted for by the large size difference. In the two systems examined, males preferred to mate with females of their own form. In sockeye, such preferences are expected because of the size difference between forms. In kokanee, such preferences are not expected based on size alone, suggesting the evolution of premating isolating mechanisms. The degree of premating isolation was positively correlated with the extent of genetic divergence between sympatric forms. The results of this study are related to existing models of sympatric speciation to hypothesize that sockeye and kokanee have diverged in sympatry. The probable differences in selection between the marine and freshwater environments coupled with the assortative mating resulting from their size difference may have caused subsequent genetic divergence. This divergence appears to have been followed by the evolution of premating isolation. / Science, Faculty of / Zoology, Department of / Graduate