Using an unplanned experiment to evaluate the effects of hatcheries and environmental variation on threatened populations of wild salmon (original) (raw)
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Advances in Marine Biology, 2007
The historical, political and scientific aspects of salmon hatchery programmes designed to enhance fishery production, or to recover endangered populations, are reviewed. We start by pointing out that the establishment of hatcheries has been a political response to societal demands for harvest and conservation; given this social context, we then critically examined the levels of activity, the biological risks, and
A quantitative framework for the analysis of habitat and hatchery practices on Pacific salmon
Ecological Modelling, 2005
We developed a model to capture the interaction of two factors (habitat and hatchery indicators) on salmon abundance, and provide a framework for evaluating alternative restoration actions for salmon in the northwestern United States, assuming specific ocean conditions and harvest rates. We modeled different hypothetical coho salmon population trajectories in Issaquah creek (King County, western Washington, USA) as a function of land-use change and hatchery supplementation. The model can be tailored to address individual problems, areas and questions.
Hatchery production of juvenile fish for release into the wild has been practiced for well over a century in an effort to increase the number of salmon available to harvest. In this study, we evaluate the net impact of the largest such program in North America, the hatchery program for pink salmon (Oncorhynchus gorbuscha) in Prince William Sound (PWS), Alaska. At the same time the hatchery program was increasing in output, there was a major change in productivity in the North Pacific so that throughout Alaska pink salmon increased dramatically in abundance between the 1970s and the 2000s. Using other regions of Alaska as reference sites, we estimate that the PWS hatchery program has increased the total catch by an average of 17 million fish, of which 8 million have been allocated to pay hatchery operating expenses. We estimate that the maximum sustainable yield (MSY) of wild spawning fish in PWS has increased slightly (28%), while in regions of Alaska without pink salmon hatchery programs the MSY has tripled. Our results support the use of a precautionary approach to future large-scale stock enhancement efforts. Résumé : La production en alevinières de poissons juvéniles destinés a ` être relâchés dans la nature est pratiquée depuis plus d'un siècle dans le but d'accroître le nombre de saumons disponibles pour la pêche. Nous évaluons l'incidence nette du plus grand programme du genre en Amérique du Nord, le programme de production en alevinières de saumons roses (Oncorhynchus gorbuscha) dans le golfe du Prince William (GPW), en Alaska. Au même moment où la production de ce programme augmentait, un changement majeur de la productivité dans le Pacifique Nord s'est produit, de sorte que l'abondance des saumons roses a ` la grandeur de l'Alaska a connu une augmentation très marquée entre les années 1970 et 2000. En utilisant d'autres régions de l'Alaska comme sites de référence, nous estimons que le programme de production en alevinières du GPW s'est traduit par une augmentation moyenne des prises totales de 17 millions de poissons, dont 8 millions ont été alloués pour payer les dépenses d'exploitation des alevinières. Nous estimons que le rendement équilibré maximum (REM) des poissons se reproduisant a ` l'état sauvage dans le GPW a augmenté légèrement (28 %), alors que dans des régions de l'Alaska sans programme de production de saumons roses en alevinières, le REM a triplé. Nos résultats appuient l'adoption d'une approche prudente dans les efforts futurs de mise en valeur des stocks a ` grande échelle. [Traduit par la Rédaction]
A conceptual framework for conservation hatchery strategies for Pacific salmonids
1999
One of the goals of fisheries conservation is to rebuild stocks. The role of the conservation hatchery is to assist the rebuilding by lessening the genetic and ecological impacts of hatchery releases on wild fish. This technical memorandum presents a conceptual framework of production strategies which can be applied in conservation hatcheries to produce fish with the wild-like attributes necessary for rebuilding depleted stocks. The background of this document is the goal of rebuilding the endangered salmon stocks of the Columbia River Basin, but the framework can be applied equally for rebuilding or improving any endangered stock. The strategies are reinforced with a specific rationale and scientifically referenced justification. Each is briefly summarized as follows: Inbreeding, outbreeding, domestic selection, and other genetic considerations. Conservation hatcheries should provide fish with minimal genetic divergence from their counterparts to maintain long-term adaptive traits. Broodstock sourcing. Conservation hatcheries should use locally adapted broodstock to maintain long-term fitness traits. Broodstock maturation and reproduction. Conservation hatcheries should manage and rear broodstock to maintain appropriate seasonal timing of maturation, ensure high quality gametes, and minimize precocious maturation of male fish. Enriched environments. Conservation hatcheries should have incubation and rearing vessels with options for habitat complexity to produce fish more wild-like in appearance, and with natural behaviors and higher survival. Growth rate modulation. Conservation hatcheries should base their goals for growth patterns of hatchery fish and size at emigration on natural population parameters. Rearing density. Conservation hatcheries should use low rearing densities to improve juvenile survival during rearing and increase adult return percentage. Anti-predator conditioning. Conservation hatcheries should have options to apply antipredator conditioning methods in hatchery rearing vessels. Release size. Conservation hatcheries should release smolts at a size which equals the size distribution of smolts in the wild population. Release time and volitional release. Fish from conservation hatcheries should be released on their own volition, and out-migrate during windows for natural downstream migration of the stock. Imprinting and homing. Conservation hatcheries should adopt practices to reduce straying, such as on-site rearing and release, and other promising imprinting or homing techniques. Habitat carrying capacity. Conservation hatcheries should program their production to accommodate the natural spatial and temporal patterns of abundance in wild fish populations. Hatchery monitoring and evaluation. A monitoring and evaluation team should be established. The team should be empowered to assess the performance of all anadromous fish hatcheries in the Columbia River Basin with respect to the objectives of the Endangered Species Act. The exact application of any guideline will depend on the physical limitations of individual hatcheries, and on the management.
Canadian Journal of Fisheries and Aquatic Sciences, 2018
Predation risk and competition among conspecifics significantly affect survival of juvenile salmon, but are rarely incorporated into models that predict recruitment in salmon populations. Using densities of harbour seals (Phoca vitulina) and numbers of hatchery-released Chinook salmon (Oncorhynchus tshawytscha) smolts as covariates in spatially structured Bayesian hierarchical stock–recruitment models, we found significant negative correlations between seal densities and productivity of Chinook salmon for 14 of 20 wild Chinook populations in the Pacific Northwest. Changes in numbers of seals since the 1970s were associated with a 74% decrease (95% CI: −85%, −64%) in maximum sustainable yield in Chinook stocks. In contrast, hatchery releases were significantly correlated with Chinook productivity in only one of 20 populations. Our findings are consistent with recent research on predator diets and bioenergetics modeling that suggest there is a relationship between harbour seal predati...
Allendorf et al. 1994: " We are not aware of a single empirical example in which (hatchery) supplementation has been successfully used as a temporary strategy to permanently increase abundance of naturally spawning populations of Pacific salmon. " Altukhov et al 1991: " Artificial reproduction, commercial fisheries, and transfers result in the impairment of gene diversity in salmon populations, and so cause their biological degradation. " Araki et al. 2007: " We show that genetic effects of domestication reduce subsequent reproductive capabilities by 40% per captive-reared generation when fish are moved to natural environments. These results suggest that even a few generations of domestication may have negative effects on natural reproduction in the wild and that the repeated use of captive-reared parents to supplement wild populations should be carefully reconsidered. " Araki et al. 2008: " Captive breeding is used to supplement populations of many species that are declining in the wild. The suitability of and long-term species survival from such programs remain largely untested, however. We measured lifetime reproductive success of the first two generations of steelhead trout that were reared in captivity and bred in the wild after they were released. By reconstructing a three-generation pedigree with microsatellite markers, we show that genetic effects of domestication reduce subsequent reproductive capabilities by 40% per captive-reared generation when fish are moved to natural environments. These results suggest that even a few generations of domestication may have negative effects on natural reproduction in the wild and that the repeated use of captive-reared parents to supplement wild populations should be carefully reconsidered. " " Our review indicates that salmonids appear to be very susceptible to fitness loss while in captivity. The degree of fitness loss appears to be mitigated to some extent by using local, wild fish for broodstock, but we found little evidence to suggest that it can be avoided altogether. The general finding of low relative fitness of hatchery fish combined with studies that have found broad scale negative associations between the presence of hatchery fish and wild population performance, should give fisheries managers pause as they consider whether to include hatchery production in their conservation toolbox. " " Accumulating data indicate that hatchery fish have lower fitness in natural environments than wild fish. This fitness decline can occur very quickly, sometimes following only one or two generations of captive rearing. " Araki, Hitoshi, Becky Cooper, and Michael S. Blouin. 2009. Carry-over effect of captive breeding reduces reproductive fitness of wild-born descendants in the wild. Biological Letters 5: (5) 621-624. " Supplementation of wild populations with captive-bred organisms is a common practice for conservation of threatened wild populations. Yet it is largely unknown whether such programmes actually help population size recovery. While a negative genetic effect of captive breeding that decreases fitness of captive-bred organisms has been detected, there is no direct evidence for a carry-over effect of captive breeding in their wild-born descendants, which would drag down the fitness of the wild population in subsequent generations. In this study, we use genetic parentage assignments to reconstruct a pedigree and estimate reproductive fitness of the wild-born descendants of captive-bred parents in a supplemented population of steelhead trout (Oncorhynchus mykiss). " The estimated fitness varied among years, but overall relative reproductive fitness was only 37 per cent in wild-born fish from two captive-bred parents and 87 per cent in those from one captive-bred and one wild parent (relative to those from two wild parents). Our results suggest a significant carry-over effect of captive breeding, which has negative influence on the size of the wild population in the generation after