Critical Need for Rigorous Evaluation of Salmonid Propagation Programs Using Local Wild Broodstock
Patrick L. Hulett, Cameron S. Sharpe, and Chris W. Wagemann
Abstract.—The use of local wild broodstocks for hatchery production, whether intended to boost natural production (supplementation) or to provide fishing opportunity (harvest augmentation), has increasingly been prescribed as a means to aid in the recovery of depressed salmonid stocks in the Pacific Northwest. Controversy over the efficacy and risks of such propagation programs continues despite years of recommendations from numerous science review panels that resolution of this issue is a critical need for development of recovery strategies. Moreover, a recent review of supplementation programs found them generally to be lacking key elements of evaluation. A particularly notable finding of that review was the absence of data on the performance of the hatchery fish in the wild or the survival of their naturally produced offspring. We propose here some key elements to be evaluated in supplementation type programs. We also report on observations from a steelhead Oncorhynchus mykiss wild broodstock program in the Kalama River (southwest Washington) that further emphasize the need for rigorous evaluation of such programs. For example, achieving basic program objectives (e.g., collecting representative broodstock, meeting rearing and release targets, and minimizing adverse ecological or genetic impacts of the propagation program on the wild population) involved unexpected logistical challenges that could hinder program success, yet could go unnoticed absent rigorous evaluation protocols. We also describe the magnitude of genetic swamping (Ryman- Laikre effect) that could result from the spawning of wild broodstock-origin adults that returned in 2002: up to 75% of the potential spawners were hatchery fish whose parents comprised only 18% of the wild population the previous generation. These observations support the contention that understanding the roles of propagated fish in the management, conservation, and recovery of salmonid fishes will not be obtained without substantial increases in the scope and rigor of evaluation of such programs.