DIVERGENCE IN FIRST GENERATION HATCHERY FISH

1) Reisenbichler, R. R. 1994. Genetic factors contributing to declines of
anadromous salmonids in the Pacific Northwest. D. Stouder, Peter Bisson,
and R. Naiman (eds.) In: 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."
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2) Jonsson, Bror, and Ian A. Fleming. 1993. Enhancement of wild salmon
populations. G. Sundnes ed.) Human impact on self-recruiting populations,
an international symposium. Kongsvoll, Norway, Tapit, Trondheim, Norway.

"Thus, the use of supplementation to enhance populations should be
carefully considered, even when only a single generation boost to a
population seems warranted.
" Differences were evident for hatchery Atlantic salmon relative to wild
salmon, with 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 averaged 65% of the breeding
success of wild males."
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3) Reisenbichler, RR. 1996. The risks of hatchery supplementation. The
Osprey. Issue 27. June 1996.

"Available data suggest 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."
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4) Verspoor, Eric. 1988. Reduced genetic variability in first generation
hatchery populations of Atlantic salmon. Can. J. Fish. Aquat. Sci. Vol. 45,
1988.

"Mean heterozygosity and number of alleles per locus were positively
correlated with effective number of adults (N) used to establish the
hatchery groups and averaged 26 % and 12 % lower, respectively, than wild
stocks. The observations are consistent with a loss of genetic variability
in the hatchery salmon from random drift caused by using small numbers of
salmon for broodstock.
"More hatchery groups appeared to be monomorphic than did wild stocks.
"Hatchery samples were 50% larger than those from the wild introducing a
bias in favor of detecting alleles in the hatchery groups compared with the
wild stocks. Thus the differences is probably underestimated.
"There is a loss of alleles in the hatchery groups with lower Ne (effective
breeding population numbers) values.
"Theory suggest that most (>99%) genetic variability will be preserved if
Ne of the broodstock is > 50.
"Losses of genetic variability can occur even in the first hatchery
generation if numbers of fish used for broodstock are not sufficient. The
average reductions in variability detected here are the same as those found
in salmon maintained in hatcheries for a number of generations. Stahl found
levels of heterozygosity to be 20% lower in Swedish hatchery salmon."
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5) Waples, Robin. Dispelling some myths about hatcheries. February 1999.
The American Fisheries Society. Fisheries Vol. 24. No. 2.

"In the Tucannon River in southeastern Washington, a (hatchery)
supplementation program for the depressed run of spring chinook salmon (O.
tshawytscha) was initiated in the mid-1980s. Founded with local broodstock,
this program aims to maintain genetic integrity of the natural population
and has a strong research and evaluation component. In spite of these
efforts, data for the early 1990s showed that, compared to the natural
adults, returning hatchery fish were younger, were smaller for the same age,
and had lower fecundity for the same size (Burgert et al. 1992). The
underlying causes of these somewhat surprising phenotypic changes are not
known; however, even if the changes were entirely an environmental response
to hatchery conditions, they still would represent a significant
single-generation reduction in productivity of the population."