I investigated juvenile coho salmon (Oncorhynchus kisutch) distribution and habitat utilization in an agricultural/urban watershed, the Salmon River, Langley, B.C. The results of my empirical work confirmed the importance of instream woody debris and undercut banks in coho distribution. I examined experimentally how juvenile coho select among patches that differ in foraging profitability and in cover availability. Ideal free distribution (IFD) models were used as the practical basis for hypotheses about habitat choice by coho salmon. My experiments were conducted in artificial stream channels and involved two different types of cover, instream and overhead, and two spatial scales. The two scales (patches within individual pools and pools within stream reaches) were used to detect the effect of different levels of sampling and information processing by the fish. Juvenile coho responded positively to food abundance both within and between pools, but they did not do it as predicted by the IFD model. Cover presence further deviated coho distribution from an IFD. Within pools, coho foraged in open patches away from cover, but preferred pools with cover when choosing between separate units. None of the alternative dispersion models that I considered, derived from the IFD, fully explained the observed dispersion patterns. Coho's ability to maximize food intake rate was not only affected by the physical complexity of their habitat, but also by intraspecific competition and interference. Subsequently, I investigated experimentally coho's response to food and different densities of woody debris in natural stream reaches. If food was abundant, coho favoured pools with sparse cover, which offers accessible refuge and leaves unobstructed foraging patches where prey and perhaps also predators are easy to detect. Pools with either high densities or total lack of woody debris attracted proportionately less fish. Earlier in the summer, fry were indifferent towards cover, but as they became older their association with instream woody debris increased. Experiments I conducted during winter indicated that water velocity and temperature affected juvenile coho downstream movement. The proportion of fish that tried to leave the experimental channels increased with water discharge and decreased with water temperature. Based on the results of my empirical and experimental work, and on information derived from comparative case studies, I evaluated the potential impact of agriculture and urbanization on coho salmon habitat. Activities associated with these types of land developments tend to: a) reduce stream channel complexity; b) eliminate off-channel fish habitat; c) increase both the magnitude and the frequency of peak flows; d) augment water sediment transport; e) alter riparian vegetation; and, f) degrade water quality. A multilayered management plan, aimed at increasing coho salmon production, was developed. The plan's management strategies were devised reflecting on the different spatial scales that watershed components have and on the connectivity processes that exist among them. / Science, Faculty of / Resources, Environment and Sustainability (IRES), Institute for / Graduate

This study examines the complex problems associated with the allocation and management of mobile salmon resources passing through politically partitioned land and sea space in southeastern Alaska and northern British Columbia. While the salmon fishing industry was found to be relatively important at the local level, it is suggested that the salmon of Canadian origin removed off Noyes Island "by Alaskan fishermen are not of critical importance to the economies of either Alaska or British Columbia when considered as a whole. Therefore, it is concluded that the Noyes Island conflict should not be allowed to jeopardize the salmon conservation programs of Canada and the United States by provoking a de facto abrogation of a mutually advantageous treaty designed to prevent the massive oceanic capture of salmon. From this case study in political geography it was determined that salmon fishing conflicts can best be understood by examining: (1) The peculiar nature of the salmon resource. (2) The state of knowledge concerning its origins and movements and the spatial implications of these movements. (3) The evolution of opposing national fisheries, (4) Interrelated political considerations. It was also found that salmon fishing conflicts could be classified into two categories based upon quantitative and ideological differences. Finally, a tentative geographic model was constructed that could serve as the basis for organizing future enquiry into salmon fishing disputes by clearly illustrating the spatial problems common to such conflicts. The model particularly emphasizes the lack of congruency between biotic and political units and the effects this has on competing, nationally organized exploitation of the salmon resource. / Arts, Faculty of / Geography, Department of / Graduate

Pacific salmon reared commercially off of the Coast of British Columbia suffer great mortality losses to Bacterial Kidney Disease (BKD), caused by the diplobacillus bacterium Renibacterium salmqninarum. This thesis investigates the effects of environmental conditions on the growth performance and disease susceptibility of salmonids reared in captivity. I found that growth rate of chinook salmon was significantly higher in fish fed to 100 compared to 67 % of satiation during the first 175 days of saltwater rearing but not during the first winter. Feed coversion rate was significantly higher for fish fed at 100 % of satiation compared to 67 % of satiation and higher during the winter compared to summer and fall, irrespective of feeding level. Mortality rates were significantly higher during the summer than during the fall or winter, irrespective of experimental treatment. The last BKD sampling period (day 263) revealed that infection rates were directly proportional to stocking densities of 1.5 to 4 kg.m⁻₃. Hatchery-reared chinook salmon held in freshwater aquaria had significantly lower hematocrit and plasma cortisol concentration increases in response to increased stocking density than did their wild counterparts. Crowding of hatchery-reared and wild chinook salmon resulted in equally increased mortality rates for both groups of fish. Day 33 plasma cortisol concentrations in Atlantic salmon held at three stocking densities were directly proportional to stocking densities of 8 to 64 kg.m⁻₃. The ability of anterior kidney lymphocytes from these fish to produce antibody-producing cells was inversely proportional to the density at which the fish were held. / Land and Food Systems, Faculty of / Graduate

I investigated the effect of turbidity on the foraging behaviour of juvenile Chinook salmon (Oncorhynchus tshawytscha) in the laboratory. Specifically, I examined a behavioural "tradeoff" between visual ability and "perceived" risk. I assessed visual ability by measuring the reaction distance of juvenile Chinook to planktonic Artemia prey. I found Chinook exhibited a log-linear decline in reaction distance with increasing turbidity. To determine the effects of turbidity and microhabitat on foraging rate, I conducted separate experiments for surface (Drosophila), planktonic (Artemia), and benthic (Tubifex) prey across a range of turbidity levels (0, 25, 50, 100, 200, 400, 800 mg•L⁻¹). Foraging rates were reduced at higher turbidity conditions for all three prey. However, for surface and benthic prey, foraging rates were also low in clear water; highest rates were attained at intermediate turbidity levels (50-200 mg•L⁻¹). The degree to which intermediate turbidities were associated with higher foraging rates was size-dependent. Smaller individuals (150-57 mm FL) exhibited relatively higher foraging rates in clear conditions than did larger individuals. However, planktonic foraging rates by juveniles were consistently high in clear water, regardless of fish size. In experiments manipulating light level independent of turbidity, I allowed salmon to forage under conditions which were either turbid, or clear but with light intensity correspondingly reduced. Foraging rates were similar between the two treatments for planktonic prey, but differed for benthic and surface prey. Generally, foraging rates exhibited by juvenile Chinook salmon could not be explained on the basis of visual ability alone. I suggest that young salmon also exhibited foraging behaviour consistent with their perception of risk to predation. In arena experiments, juvenile Chinook distributed themselves randomly in turbid conditions; in clear conditions they associated with the bottom. When bird and fish predator models were introduced the fish altered their spatial distribution, occupying deeper regions regardless of turbidity. However, their response in turbid conditions was less marked and lasted for a shorter time. Turbidity apparently mitigated the perceived risk of predation in juvenile Chinook. I developed a conceptual tradeoff model that predicted the general effect of turbidity on foraging behaviour. Assuming differences in either prey quality or perceived risk of predation in three microhabitats (surface, water column, bottom), the model resolved the apparent dissimilarities between planktonic and other foraging behaviours. Perceived risk of Chinook to predation was significantly different between surface and water column microhabitats. When exposed to a non-visual "fixed-risk" stimulus (sound), salmon apparently perceived less risk as turbidity increased. I conclude that in turbid waters juvenile salmon exhibit foraging behaviour in a manner consistent with a tradeoff between their visual ability and perceived risk. / Science, Faculty of / Zoology, Department of / Graduate

The locomotor responses of juvenile and adult sockeye salmon (Oncorhynchus nerka) to concurrent changes in temperature and salinity were examined in a controlled laboratory setting. I hoped to better understand how these environmental factors influence the coastal movements of migrating salmon. Juvenile sockeye were captured during the downstream migration from Great Central Lake on Vancouver Island, British Columbia, Canada. The fish were acclimated for 1 wk at 10°C, 20 ppt, and then tested in annular activity tanks. Spontaneous locomotor movements were recorded during concomitant changes in temperature and salinity using infra-red photometry. Raising the water temperature by 4°C in 1 h caused a dramatic increase in locomotor activity. Decreasing temperature by 4°C or varying salinity by 10 ppt from the control levels did not influence routine swimming speed and there was no interaction between factors. Adult sockeye homing to the Fraser River, British Columbia, Canada were captured along the nearshore migration route in two oceanographically distinct regions. Three groups of fish were collected from the cold, saline waters of Queen Charlotte Strait, near the northern end of Vancouver Island. Two groups of sockeye were captured within 60 km of the Fraser River in the warmer, less saline waters of the Strait of Georgia. The adults were acclimated 2-5 days at 12°C, 30 ppt and locomotor activity was tested in annular activity tanks. Routine swimming speed and turning rate rose when the water temperature was raised by 4°C in 2 h, however, locomotor activity was not influenced by decreasing temperature. In addition, decreasing salinity by 10 ppt in 2 h had no effect on swimming activity of adult sockeye and there was no interaction between the two factors. Fish taken from the Strait of Georgia generally showed a less dramatic response to increasing temperature than adults captured in Queen Charlotte Strait. Results indicate that warm coastal temperatures may influence the nearshore migration of both juvenile and adult sockeye salmon. / 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

Since 1995, California State Fish Hatcheries (Feather River, Nimbus, and Mokelumne) and Coleman National Fish Hatchery have raised approximately 29 million 4 fall run Central Valley Chinook salmon (Oncorhynchus tshawytscha) per season for stock enhancement. From April through June, fish are acclimated in net-pens prior to release at one of three sites: the Carquinez Strait at Conoco Phillips (CP), the mouth of the Napa River at Mare Island (MI), and the San Joaquin River at Jersey Point (JP). Striped Bass, Marone saxatilis, are known to congregate at the release location to feed on the hatchery fish as they enter the Delta and Bay, and are suspected to be reducing numbers of Chinook recruitment. Dual-Frequency Identification Sonar (DIDSON) was used to capture video-like images to enumerate and estimate sizes of potential predators in the area. Stomach analysis was used to obtain consumption rate data and a simple model was used to estimate predator impacts on the hatchery fish. Data was collected in 2011 and 2012. In 2011 the striped bass population at CP was significantly larger than MI (p=0.009) and JP (p=0.038) and in 2011 , and MI (p=0.046) in 2012. Predators were significantly smaller (range 11.8-61.7 em, mean 34.6 em in 2011 ; 21-67 em, 42.9 in 2012) atJP (p<0.001). Average size predator at MI was 47.3 em (range 31-59 em) in 2011 and 50.9 em (range 33-73 em) in 20 12; and at CP was 48.3 em (range 16-77 em) in 2011 and 52.7 em (range 31-78 em) in 2012. On average an estimated 2.2% of hatchery fi sh are consumed each year by striped bass and predator impacts are greatest at CP (p<0.001). Changing the release site often could improve salmon survival by decreasing predator attraction to the site and reducing immediate predator-prey encounters.