SALMON SUPPLEMENTATION: DEMOGRAPHY, EVOLUTION, AND RISK ASSESSMENT[1]

Goodman, Dan. 2003. Salmon supplementation: demography, evolution, and risk assessment. Prepared for presentation at Amer. Fish. Soc. symp.: Propagated Fishes in Resource Management.

ABSTRACT

Salmon supplementation aims to integrate the wild and hatchery populations by deliberately allowing returning hatchery adults to stray to the natural spawning ground, and, in some protocols, by taking adults of natural spawning origin for hatchery broodstock. If the population becomes truly integrated, this puts a different light on concerns about effects of "hatchery" fish on "wild" fish, since the result will just be one population with a common gene pool. In this integrated population, the basis for an assessment of the genetic effect would be a comparison of the natural spawning performance of the supplemented population compared to that of an unsupplemented "control." Actual, experimental supplementation programs have not yet measured the right quantities with the right design to provide an empirical assessment. Theoretical modeling shows that an integrated breeding program still has the potential for domestication selection during the hatchery phase which can reduce the natural spawning performance of the stock relative to its pre-supplementation performance. All other things being equal, the erosion of natural spawning performance will increase with the amount of outplanting and the amount of use of hatchery origin fish for hatchery broodstock. This should put more of a premium on adherence to a definite protocol, and on effective monitoring of actual supplementation experiments in order to quantify the inherent tradeoffs between competing adaptations to the life cycle resulting from hatchery spawning versus the life cycle resulting from natural spawning.

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[1] Prepared for presentation at American Fisheries Society Symposium, "Propagated Fishes in Resource Management," Boise, June 16, 2003.