Chinook Salmon

Of the many technologies used by the Canadian Salmonid Enhancement Program (SEP, established in 1979), hatcheries have been a major tool used to increase the freshwater survival of selected wild, native stocks of coho, chinook and chum salmon, both to address conservation concerns and to provide fishing opportunities. SEP hatcheries have contributed substantially to the fisheries for coho and chum

Fall-run Chinook salmon (Oncorhynchus tshawytscha) from the Sacramento–San Joaquin River system form the backbone of California's salmon fishery and are heavily subsidized through hatchery production. Identifying temporal trends in the relative contribution of hatchery-versus wild-spawned salmon is vital for assessing the status and resiliency of wild salmon populations. Here, we reconstructed the proportion of hatchery fish on natural spawning grounds in the Feather River, a major tributary to the Sacramento River, using strontium isotope (87 Sr/ 86 Sr) ratios of otoliths collected during carcass surveys from 2002 to 2010. Our results show that prior to the 2007–2008 salmon stock collapse, 55%–67% of in-river spawners were of hatchery origin; however, hatchery contributions increased drastically (89%) in 2010 following the collapse. Data from a recent hatchery marking program corroborate our results, showing that hatchery fish continued to dominate (90%) in 2011–2012. Though the rebound in abundance of salmon in the Feather River suggests recovery of the stock postcollapse, our otolith chemistry data document a persistent decline of wild spawners, likely leading to the erosion of locally adapted Feather River salmon populations. Résumé : Les saumons quinnats (Oncorhynchus tshawytscha) à migration automnale du réseau du fleuve Sacramento et de la rivière San Joaquin forment l'épine dorsale de la pêche aux saumons en Californie et sont fortement soutenus par la production en alevinières. La détermination des tendances dans le temps des apports relatifs de saumons issus d'alevinières et de saumons nés dans la nature est cruciale pour évaluer l'état et la résilience des populations de saumons sauvages. Nous avons reconstitué la proportion de poissons issus d'alevinières dans des aires de frai naturelles dans la rivière Feather, un important affluent du fleuve Sacramento, en utilisant les rapports d'isotopes de strontium (87 Sr/ 86 Sr) d'otolites prélevés durant des relevés de carcasses de 2002 à 2010. Les résultats montrent que, avant l'effondrement des stocks de saumons de 2007–2008, de 55 % à 67 % des frayeurs dans la rivière provenaient d'alevinières; toutefois, l'apport d'alevinières a connu une augmentation très marquée (89 %) en 2010 dans la foulée de l'effondrement. Les données tirées d'une campagne récente de marquage en alevinière corroborent ces résultats, démontrant que les poissons issus d'alevinières sont toujours prédominants (90 %) en 2011–2012. Si la remontée de l'abondance des saumons dans la rivière Feather semble indiquer un rétablissement du stock à la suite de l'effondrement, nos données sur la chimie des otolites documentent un déclin soutenu des géniteurs sauvages, qui mène vraisemblablement à l'érosion des populations de saumons adaptées aux conditions locales de la rivière Feather. [Traduit par la Rédaction]

Stream restoration has become a major focus of conservation efforts with millions of dollars spent each year on efforts aimed at recovering imperiled species; however, for animals with complex life-history strategies, this reliance on stream restoration for increasing overall survival requires that several key assumptions be met. We addressed fundamental uncertainties of the current focus on tributary restoration for recovery of endangered Snake River spring/summer Chinook salmon (Oncorhynchus tshawytscha): 1) is there potential for improving habitat in tributary streams, 2) what magnitude of early survival improvement can be expected based on stream restoration, and 3) will incremental increases in early survival be sufficient to ensure viability of the populations that compose the Evolutionarily Significant Unit (ESU)? We combined simple mechanistic habitat models, population viability measures, and categorical filters to quantify the potential for increasing total life-cycle survival (TLCS) across all 32 populations (ESU), based on increases to early freshwater survival, predicted to occur in response to restored tributary condition. A wide gap remains between how much survival improvement is needed, versus what is likely to occur under tributary restoration; tributary restoration has the potential to increase survival to the necessary minimum for only four populations in the ESU while the remaining populations (84%) still fall far below the survival needed for future viability. In addition, across the ESU; on average, a 171% increase in TLCS is necessary, whereas only ~106% appears possible. A recovery strategy for these salmon that relies largely on tributary restoration, to mitigate for known mortality imposed at other life stages (e.g., migration through hydropower dams) is risky and has a low probability of success. For animals with complex life cycles and exhibiting long migrations, stream restoration efforts may be ineffective and misplaced, if the targeted life stage is not limiting or unresponsive, and/or if there is little potential for increasing survival overall. We demonstrate both an approach for, and the importance of, completing a comprehensive a prior evaluation of restoration potential, such that scarce resources can be allocated to efforts with the greatest potential and the least amount of risk.

To further characterize the toxicological risk associated with chemical contaminants in Great Lakes fish, a multigeneration rat reproduction study was designed. Mature chinook salmon (Oncorhynchus tsawytscha), collected during the Fall 1991 spawning runs from Sydenham River, Lake Huron, and Credit River, Lake Ontario, were filleted, lyophilized, and incorporated into standard rat diets at 25% (w/w) or 100% (w/w) of the normal protein compliment [casein, 20% (w/w)]. This resulted in diets composed of 5 or 20% (w/w) lyophilized fish and estimated daily fish intakes by the rats at levels approximately 15- and 60-fold greater, respectively, than the current estimate for the Canadian public for all fish and seafood. Both fresh and lyophilized fish were analyzed for the following groups of contaminants: halogenated aromatic hydrocarbons [polychlorinated biphenyls, dibenzodioxins, and dibenzofurans (PCBs, PCDDs, PCDFs)], polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides, m...