Rainbow trout (Salmo gairdneri) from two wild stocks native to British Columbia, and a non-native domestic strain were reared under varying conditions to examine effects of growth rate and body size, genetic stock, and photoperiod on the incidence and timing of testis development. The ratio of gonad weight to body weight (Gonadosomatic index) was found to be useful for separating mature and immature male fish and for determining the onset of gonadal development. In Premier lake fish testis development began one year before the expected date of spawning. At this time, signs of maturation were evident primarily among males that reached a body weight of between ten and twenty grams, whereas most of the fish smaller than this "critical" size remained immature (i.e. no testis developmment). Apparently, this critical size must be reached by a certain time of the year. Thus, a time 'window' exists wherein fish achieving a certain size begin preparation for spawning the following year. Altering photoperiod regime during the time window had no effect on the incidence of sexual precociousness, but did delay spermatogenesis by an undetermined length of time. / Science, Faculty of / Zoology, Department of / Graduate

A deterministic simulation model is used to explore the relationship between juvenile pink, chum and coho salmon growth and size-related survival in the Fraser River estuary. Parameters most sensitive to change are identified and the results related to proposals for enhancement. These results suggest that increasing the initial size of enhancement pink and chum fry, relative to the size of wild fry, prior to seaward migration and releasing them early in the spring may increase their chances of survival. If increasing total (enhancement plus wild) fry density decreases fry growth rate, the presence of enhancement fry in the estuary could reduce the survival chances of wild fry. The decrease in wild stock survival may not be apparent from estimates of adult return for many years due to errors in measurement and to the effect on survival of environmental variability. The model can be used to suggest and evaluate enhancement proposals. Areas needing further research are also indicated. / Science, Faculty of / Zoology, Department of / Graduate

Juvenile rainbow trout (Salmo gairdneri Richardson) from the Lardeau River in southeastern British Columbia were studied in both their natural environment and stream tanks. In the river, highest densities of recently emerged trout occurred in areas with overhanging cover, shallow depth and minimal current. Older, underyearling trout were generally found in regions with smaller bottom particle size than yearlings; both age classes avoided fast current areas. Young trout migrated from the Lardeau River to Kootenay Lake during spring and summer. Except during these seasons trout were larger and more abundant in the upper versus the lower river; this was probably a result of better rearing habitat and higher biological productivity in the upper river. Trout fed almost exclusively on drifting organisms. Lake origin drift was an important food to riverine trout during summer; kokanee (Oncorhynchus nerka) eggs and fry were significant during fall and spring respectively. In stream tanks, where it was possible to manipulate prey populations, live prey were consumed significantly more than the same species when dead, suggesting that prey body movement was an important prey characteristic. In both the field and stream tanks, trout consumed prey within a discrete size range with larger fry generally consuming bigger prey than smaller fry. Further work is suggested which would improve our understanding of the feeding ecology of stream rearing trout. / Science, Faculty of / Zoology, Department of / Graduate

Memoria para optar al título profesional de Ingeniero Agrónomo / No disponible a texto completo / El objetivo general de este ensayo fue evaluar el efecto de la modificación de la composición en ácidos grasos de la dieta, sobre el contenido de ácidos grasos ω-3 eicosapentaenoico (EPA), docosahexaenoico (DHA), ácidos grasos ω-6 Linoleico y Araquidónico; comportamiento productivo y características de calidad de canal, en trucha arcoíris (Oncorhynchus mykiss). Para modificar la composición en ácidos grasos de la dieta el aceite de soja, que es la principal fuente de grasas vegetales en las dietas comerciales actuales, fue reemplazado parcialmente por aceite de lino. Los peces con un peso vivo promedio inicial de 1126 g fueron alimentados por 10 semanas, mientras permanecían en 6 balsas-jaula en condiciones comerciales. Los peces fueron muestreados al azar cada 5 semanas para medir peso vivo, longitud horquilla, peso canal, peso vísceras, peso hígado y se identificó el sexo. Al mismo tiempo, se tomaron 9 filetes por cada tratamiento los que se mantuvieron congelados a -20°C hasta su análisis. El incremento de ácido α-linolénico en la dieta, resultó en un incremento significativo (P<0,05) de este ácido graso en el filete (0,74 vs. 0,60 control); sin embargo, no se observó diferencias significativas (P>0,05) en el contenido de EPA (0,41 vs. 0,43 control) ni DHA (0,49 vs. 0,55 control). Existió un menor contenido (P<0,05) de ácido linoleico en los filetes del grupo control (4,44 vs. 5,00 control), valores expresados como g de cada ácido graso en 100 g de filete Se concluye que la adición de un 20 % de aceite de lino en reemplazo de aceite de soja en la dieta de trucha arcoíris, disminuye significativamente el contenido de ácido linoleico y aumenta significativamente el contenido de ácido α-linolénico en el filete luego de 10 semanas de alimentación; determinando una mayor relación ω-3/ω-6 (P<0,05) en el grupo con aceite de lino (0,44±0,06 vs 0,37±0,05), sin modificar significativamente el contenido de EPA y DHA. / The objective of the present study was to evaluate the effects of changing the proportions of dietary fatty acids ω-3 EPA, DHA and ω-6 linoleic, arachidonic acid over rainbow trout (Oncorhynchus mykiss) fatty acid profile, productive performance and fillet composition. Soybean oil, the main source of vegetable fat in current commercial diets, was partially replaced for linseed oil to modify the fatty acid profile of the diet. Fish were kept in sea-cages and reared under regular commercial conditions; initial fish live weight was 1126 g and the experimental diets were supplied during 10 weeks. Fish samples were randomly taken from each cage every 5 weeks to measure live weight, fork length, carcass weight, guts and liver weight, sex was identified, at the same time 9 fish fillets were collected and frozen (-20ºC) until further analysis. The increase in dietary α-linolenic acid generated a significant (p<0.05) elevation of this fatty acid in fish fillet (0.74 vs 0.60); however, EPA and DHA levels were not affected by treatment and showed similar values when compared to the control (0.41 vs. 0.43 and 0.49 vs. 0.55). A minor contents (P < 0.05) of linoleic acid in the fillet existed of the control (4.44 vs. 5.00 control), when expressed as grams of fatty acid per 100 grams of fillet. In conclusion, replacing 20% soybean oil by linseed oil in rainbow trout diet, significantly decreased linolenic acid and significantly increased α-linolenic acid concentrations in fish fillets after 10 weeks of feeding; determining a higher ω-3 / ω-6 proportion in the fillet of fish fed linseed oil (0,44±0,06 vs 0,37±0,05), with no significant effect on EPA and DHA content.

<p> The development of Na+ and Ca++ transport, ammonia excretion, and respiration in larval rainbow trout were studied over the period of yolk sac absorption and shortly after the onset of exogenous feeding. The gills and the yolk sac epithelium of larvae were examined for any indication of the presence of mitochondria-rich cells and/ or Na-K-ATPase activity. </p> <p> Whole body Na+ content of the larvae increased throughout yolk sac absorption and after the onset of exogenous feeding. During this period there was an increase in Na+ influx, efflux, transporter capacity Umax> and transporter affinity (Km). Jmax increased 4.6 times during yolk sac absorption, and increased another 2.8 times 248 degree·days after the onset of exogenous feeding. Km decreased over the first 168 degree·days and stayed constant for the remainder of the experimental period. The gills were the primary site of Na+ efflux. Na+ accumulation from the water began the first day post hatch. </p> <p> Ca++ transport capacity increased throughout yolk sac absorption, but then decreased after the onset of exogenous feeding. Jmaxca++ exhibited a 15.5 fold increase over 257 degree·days, which then decreased to 30% of that value after exogenous feeding commenced. There was a 162 fold increase in Ca++ Km over yolk sac absorption, which then decreased 15.6 times after the onset of exogenous feeding. Whole body Ca++ began to increase approximately 200 degree·days post-hatch and exhibited a large increase after the onset of exogenous feeding. It is possible that during yolk sac absorption the larvae does not begin to accumulate Ca++ from the external environment until its internal reserves are depleted, and with the onset of feeding the larvae then obtains its Ca++ from its diet. </p> <p> Ammonia excretion in larval trout increased 3.6 times over yolk sac absorption, and increased another 2.8 times after exogenous feeding commenced. There was no evidence of a link between Na+ uptake and NJ-:4+ excretion in larval fish as NJ-:4+ excretion was not stimulated in response to increasing external Na+ concentrations. Measurements of the ammonium concentration at different surfaces of the larvae revealed a larger ammonium concentration next to the gills than next to the yolk sac and skin. This may indicate that the gills are the primary site for ammonia excretion in the larval fish. </p> <P> Initially, branchial and cutaneous surfaces contributes to respiration, but as the gills grow and develop and the yolk sac decreases in size and the skin thickens, the contribution of the gills to this function increases. </p> <p> The gills of first day hatchlings are comprised of gill arches and filaments. Lamellae do not begin to develop until a few days after hatching. The gill filaments contain mitochondria-rich cells and have Na-K-ATPase activity as determined through binding of the fluorescent dye anthroylouabain. The yolk sac epithelium contained cells with concentrated regions of mitochondria, but significant Na-K-ATPase activity was not detected when compared to branchial staining. </p> / Thesis / Master of Science (MSc)

Salmonids are a diverse group of fishes whose common ancestor experienced an evolutionarily important whole genome duplication (WGD) event approximately 90 MYA. This event has shaped the evolutionary trajectory of salmonids, and may have contributed to a proliferation of the repeated DNA sequences known as transposable elements (TEs). In this work I characterized repeated DNA in five salmonid genomes. I found that over half of the DNA within each of these genomes was derived from repeats, a value which is amongst the highest of all vertebrates. I investigated repeats of the most abundant TE superfamily, Tc1-Mariner, and found that large proliferative bursts of this element occurred shortly after the WGD and continued during salmonid speciation, where they have produced dramatic differences in TE content among extant salmonid lineages. This work provides important resources for future studies of salmonids, and advances the understanding of two important evolutionary forces: TEs and WGDs. / Graduate / 2019-04-19

Flavobacterium psychrophilum est l’agent pathogène des flavobactérioses d’eau froide touchant essentiellement les salmonidés dont la truite arc-en-ciel Oncorhynchus mykiss d’élevage. Cette bactérie Gram négative a un très fort impact économique en aquaculture car elle peut causer jusqu'à 70 % de mortalité dans les bassins d’élevage. La flavobactériose se décline sous deux formes pathologiques : la maladie de l’eau froide touchant les poissons adultes et le syndrome de l’alevin de truite arc-en-ciel touchant les juvéniles.Au cours de se travail, une méthode de PCR quantitative a été proposée. Elle permet en moins de trois heures de détecter et de quantifier un nombre de copies du gène codant l’ARNr 16S de la bactérie dans les tissus du poisson. Cette méthode a été testée sur différentes suspensions bactériennes (F. psychrophilum, autres flavobactéries, autres pathogènes) afin d’en valider la spécificité. La sensibilité de la méthode de détection a été évaluée à 1 et 2 bactéries par PCR en fonction de la matrice biologique utilisée.Une étude écotoxicologique a été menée et montre d’une part que F. psychrophilum est une bactérie hyper-sensible au cadmium comparée aux autres bactéries Gram négatives. Sa croissance est diminuée d’un facteur 2 en présence d’une contamination au Cd à 0,4 µM. D’autre part, nous avons constaté qu’une contamination de truites juvéniles par 1 µg CdCl2/L (2 mois) et une injection de 5 × 107 flavobactéries par individu (1 mois) ne provoque aucune mortalité. L’expression génique mesurée sur ses poissons démontre que le cadmium peut avoir des effets contradictoires sur le système immunitaire du poisson, pouvant soit exacerber ou diminuer la réponse immunitaire selon l’organe considéré. Un travail comparatif de la prévalence de la flavobactérie dans 7 sites aquacoles d’Aquitaine a démontré que la flavobactérie est omniprésente et que sa pathogénicité est contrôlée par le système immunitaire des poissons en bonne santé apparente. L’expression génique mesurée sur les poissons malades et apparemment sains nous apporte deux informations importantes : 1/ les gènes codant pour la métallothionéine A et l’interleukine 1-β sont de bons bio-marqueurs de la maladie et 2/ la répression des gènes codant pour le complexe majeur d’histocompatibilité 2-β, le facteur de croissance transformant β, le cluster de différentiation 8-α et l’immunoglobuline T dans la rate des poissons malades montre un effondrement du système immunitaire acquis nous permettant d’émettre l’hypothèse que ce phénomène déclenche l’apparition de la maladie. Ainsi, F. psychrophilum aurait un comportement de pathogène à virulence latente.Afin d’imaginer de nouvelles mesures prophylactiques et pour mieux comprendre la pathogénicité de la bactérie, une analyse du protéome de la membrane externe couplée à l’annotation du génome séquencé a été effectuée. Il a été identifié entre autres 1/ des protéines d’adhésion et d’invasion des tissus et 2/ des protéines d’acquisition de métabolites de l’hôte. De plus, un nombre important de protéines immunogènes chez la truite potentiellement utilisable dans un cocktail vaccinant a été détecté. Afin de chercher un vecteur pour ce cocktail, des nanoparticules d’acide γ-glutamique et phénylalanine d’environ 100 à 200 nm de diamètre ont été synthétisées. Ces dernières constituent une approche séduisante pour vacciner les poissons avec des antigènes de F. psychrophilum encapsulés puis incorporés dans la nourriture. / Flavobacterium psychrophilum is the causative agent of cold water flavobacteriosis, a condition affecting mostly salmonid fish, including the farmed rainbow trout Oncorhynchus mykiss. This Gram negative bacterium can cause up to 70% mortality in breeding tanks and has a very strong economic impact on the fish farming industry. Flavobacteriosis can take two pathological forms: the cold water disease affecting adult fish and the rainbow trout fry syndrome affecting juveniles.In the present study, a method of quantitative PCR was devised that allowed for the detection and the quantification, within three hours, of the 16S rRNA copy number in fish tissues. This method’s specificity was confirmed through the use of various bacterial suspensions (F.psychrophilum, others flavobacteria and others pathogens) and its detection limit was estimated to be 1 and 2 bacteria in broth and in biological matrices, respectively.An ecotoxicological study was then performed that showed that, on the one hand, F. psychrophilum is cadmium hypersensitive compared to others Gram negative bacteria because its growth rate, compared to a control, is decreased by a factor 2 at a cadmium concentration of 0,4 µM. On the other hand, we observed that subjecting rainbow trout juveniles to a concentration of 1 µg CdCl2/L for2 months prior to an injection of 5 × 107 F. psychrophilum by fish didn’t lead to any mortality. The gene expression which was measured on these fish demonstrated that cadmium can have contradictory effects on the immune system of fish, which could enhance or decrease the immune response depending of the organ. A comparative work of the prevalence of flavobacteria in 7 fish farms within the Aquitaine region (France) demonstrated that the bacterium was endemic and present in asymptomatic fish. Gene expression levels were measured on diseased and asymptomatic fish and demonstrated that the genes metallothionein A and interleukine 1-β were good biomarkers of the disease and that repression of the genes major histocompatibility complex 2-β, transforming growth factor -β, cluster of differentiation α and immunoglobulin T in the spleen of diseased fish was indicative of a collapse of the acquired immune system. We therefore hypothesized that this event marked the beginning of the disease and that F. psychrophilum is mostly an opportunistic pathogen.To prepare the development of new prophylactic techniques and to understand better the bacterium pathogenicity, an analysis of the outer membrane proteome coupled with sequencing of the bacterial genome was also performed. Furthermore, a significant number of immunogenic proteins were identified as good candidates for the preparation of a vaccine. Finally, γ-glutamic acid and phenylalanine nanoparticles of about 100 - 200 nm in diameter were synthesized to serve as potential vector for this vaccine. These nanoparticles should be tested to administrate F. psychrophilum antigens to fish through the digestive route.

The aim of this thesis was to examine the influence of nitrite on fish. Influence of nitrite was evaluated on the basis of acute and sub-chronic toxicity tests results on rainbow trout (Oncorhynchus mykiss). The effects of nitrite were also observed in wels catfish {--} albino (Silurus glanis). On the basis of the results of acute toxicity tests, values of lethal concentration of nitrite for rainbow trout (Oncorhynchus mykiss) (96hLC50 = 11.2 mg.l-1 NO2-) and for wels catfish {--} albino (Silurus glanis) (96hLC50 = 15.8 mg.l-1 NO2-) were calculated. Using results of acute toxicity test for rainbow trout (Oncorhynchus mykiss) and with respect to legislative requirements, concentrations of nitrite for sub-chronic toxicity test were selected. The results of sub-chronic toxicity test showed that nitrite concentration of 3 mg.l-1 NO2- during 28-day exposition caused 65 % fish mortality. This concentration also caused growth rate decrease compared to control. Growth rate among fish exposed to concentrations lower then 3 mg.l-1 NO2- was comparable to control. Among fish exposed to nitrite concentration of 0.6 mg.l-1 NO2- and higher nitrite accumulation in muscle and in blood plasma was observed. Haematological examination showed statistically significant decrease of haematocrit value and concentration of haemoglobin and increase of the number of leukocytes in experimental fish. Other measured haematological parameters (Ery, MCV, MCH and MCHC) were comparable with control.

Interactions between fish utilizing nearshore habitats of the Fraser River estuary were investigated by field observations and laboratory experiments. Chum salmon fry (Oncorhynchus keta) were the most abundant salmonid captured between April and June. Non-salmonid species captured included: threespine stickleback (Gasterosteus aculeatus), prickly sculpin (Coitus asper), and peamouth chub (Mylocheilus caurinus). Potential predators included: prickly sculpin, and northern squawfish (Ptychocheilus oregonensis), but few had been feeding on fish. Chum fry fed predominantly on surface insects but the proportion of benthic prey in the diet increased over time. Stickleback shared the greatest diet overlap with chum fry. Interactions between two dissimilar prey, chum fry and threespine stickleback, and a predator, cutthroat trout (Oncorhynchus clarki) were investigated in the laboratory. Prey response to hungry and satiated predators was related to the degree of risk. Although attack rates by trout on chum and stickleback were similar, trout captured more stickleback than chum, but consumed both prey at similar rates. I tested the hypotheses that prey foraging efficiency is reduced in the presence of a predator and increased in the presence of alternate prey. When alone, chum fed on surface Drosophila and mid-water Daphnia, while stickleback fed on benthic Tubifex and Daphnia. The feeding efficiency of chum increased in the presence of stickleback and decreased in the presence of trout. Hatchery and wild chum showed opposite dietary shifts in the presence of trout. Hatchery chum shifted from surface to mid-water feeding and the number of fish feeding significantly decreased. Wild chum fed at the surface, at significantly decreased feeding rates. In the presence of stickleback and trout the feeding behaviour of chum was similar to that when chum were alone. Stickleback feeding behaviour was not affected by presence of trout or chum. Chum and stickleback detected Daphnia faster than Drosophila or Tubifex, and chum responded to Daphnia significantly faster than stickleback. Foraging time per item was significantly less for chum than stickleback. Habitat use by fish prey was investigated in the presence and absence of trout and alternate prey. Wild chum shifted from mid-water to the surface in the presence of trout, but returned to mid-water when stickleback were present. Stickleback fed in bottom habitats regardless of the presence of trout or chum. When prey were confined to specific depths in the water column, trout attacked chum more frequently than stickleback in all locations and attacked both prey more frequently within 24 cm of the substrate. Movement by prey did not affect the attack rate. When given a choice between a food-rich open water habitat and a food-deficient vegetated habitat in the presence of trout and alternate prey, chum and stickleback used vegetated refugia significantly more in the presence of trout. Alternate prey presence decreased the proportion of chum but increased the proportion of stickleback using vegetation. Behavioural responses to avoid predation significantly reduced the foraging efficiency of prey. Chum showed stronger responses to trout than stickleback. The presence of stickleback reduced the effect of predation on foraging efficiency. Possible explanations for the positive effect of stickleback on chum feeding efficiency were experimentally examined including: social facilitation, reduced intraspecific competition, and the calming influence of stickleback on chum behaviour ("dither"). The results suggest that stickleback have a calming influence on chum behaviour and that mixed species feeding groups may reduce intraspecific competition. / Science, Faculty of / Zoology, Department of / Graduate

Pacific salmon