RAPID GENETIC CHANGES IN HATCHERY FISH AND THE EFFECT ON REPRODUCTIVE SUCCESS IN STREAMS

Reisenbichler, R.R. 1994. Genetic factors contributing to declines of anadromous salmonids in the Pacific Northwest. Editors: D. Stouder and R. Naiman. Pacific Salmon and Their Ecosystems. Chapman Hall, Inc.

“Gene flow from hatchery fish also is deleterious because hatchery populations genetically adapt to the unnatural conditions of the hatchery environment at the expense of adaptedness for living in natural streams. This domestication is significant even in the first generation of hatchery rearing.”

Jonsson, Bror and Ian A. Fleming. 1993. Enhancement of wild salmon populations. In: G. Sundnes (editor). Human impact on self-recruiting populations, an international symposium. Kongsvall, Norway.

“Thus, the use of supplementation to enhance populations should be carefully considered, even when a single generation boost to a population seems warranted. Differences were evident for hatchery Atlantic salmon relative to wild salmon, with a common genetic backgrounds, in breeding success after a single generation in the hatchery. Hatchery females averaged 80% of the breeding success of wild females and hatchery males were 65% of the breeding success of wild males.”

Reisnbichler, R.R. 1996. The risks of hatchery supplementation. The Osprey. No. 27. June 1996.

“Available data suggests progressively declining fitness for natural rearing with increasing generations in the hatchery. The reduction in survival from egg to adult may be about 25% after one generation in the hatchery and 85% after six generations. Reductions in survival from yearling to adult may be about 15% after one generation in the hatchery and 67% after many generations.”

Recovery Science Review Panel Report. August 30- September 1, 2004. NMFS, Northwest Science Center. Seattle, WA.

“We believe that the loss of fitness in the wild is an inevitable consequence of adaptation to hatcheries and evidence suggests that this loss can occur even in the initial generation of breeding stock.” (page 2)

Reisenbichler, R.R., F.M. Utter, and C.C. Krueger. 2003. Genetic concepts and uncertainties in restoring fish populations and species. In: Strategies for Restoring River Ecosystems: Sources of Variability and Uncertainty in Natural and Managed Systems. Am. Fish. Soc. 149-183.

“The value of genetic diversity notwithstanding, diversity can be excessive and can compromise adaptedness or fitness. Theoretical treatments illustrate that fitness is compromised by substantial gene flow from populations that are poorly adapted for local conditions (Hendry et al. 2001). Reduced, not increased, fitness has been observed when genetically distinct populations of the same species hybridize (Reisenbichler and McIntyre 1977; Philipp 1991; Gharrett et al. 1999). Indeed, Reisenbichler and McIntyre (1977) found reduced survival in hybrids between hatchery and wild steelhead even though the hatchery population had been derived exclusively from the wild population only two generations before the study. These and similar findings illustrate that hatchery populations genetically adapt to the conditions of a hatchery program, which are very different from natural conditions, and that such domestication apparently comes at the expense of adaptedness for natural production. (page 151)

Hey, Jody; Ernest L. Brannon; Donald E. Campton; Roger W. Doyle; Ian A. Fleming; Michael T. Kinnison; Russell Lande; Jeffery Olsen; David P. Philipp; Joseph Travis; Chris C. Wood, and Holly Doremus (Facilitator). May 16, 2005. Considering life history, behavioral and ecological complexity in defining conservation units for Pacific salmon, an independent panel report, requested by NOAA Fisheries.

“A strict phylogenetic or taxonomic approach overlooks the fact that even within a single generation, hatchery and wild fish differ because of their responses to dissimilar environments.” (page 7)

Reisenbichler, R. R. and S.P. Rubin. 1999. Genetic changes from artificial propagation of Pacific salmon affect the productivity and viability of supplemented populations. ICES Journal of Marine Science, 56: 459-466.

“All five of the studies in natural streams suggest the same conclusion: hatchery prgrammes that rear steelhead or chinook salmon for 1 year or longer before release genetically change the population and thereby reduce reproductive success when these fish spawn in natural systems.” (page 463-464)

“Apparently, domestication selection is often intense. The fitness of stream-type chinook salmon was diminished after four generations of culture, despite continuous gene flow from the wild population (on average, wild fish comprised 38% of the hatchery broodstock). (page 464)

Kostow, Kathryn, E. 2004. Difference in juvenile phenotypes and survival between hatchery stocks and a natural population provide evidence for modified selection due to captive breeding. Can. J. Fish. Aquat. Sci. 61: 577-589

“A difference in fitness between the new hatchery stock and naturally produced fish was indicated by significant survival differences. Acclimation of the new hatchery stock in a ‘seminatural’ pond before release was associated with a further decrease in relative smolt-to-adult survival with little increase in phenotypic similarity between the natural and hatchery fish. These results suggest that modified selection begins immediately in the first generation of a new hatchery stock and may provide a mechanism for genetic change.” (From the Abstract)

“The processes indicated by these results can be expected to lead to eventual genetic divergence between the new hatchery stock and its wild source population, thus limiting the usefulness of the stock for conservation purposes to only the first few generations.” (page 588)