Are Hatchery Effects Forever? - Use of Hatchery Stocks to Reintroduce Extirpated Coho Salmon to the Interior Columbia Basin

Coho salmon were once abundant throughout much of the Columbia River basin.  However, over-fishing, habitat loss and mismanagement during the 1900’s, lead to extirpation of all natural populations upstream of The Dalles Dam.  This loss of an integral member of the family of salmon species was untenable to the Columbia River treaty tribes.  As their own fisheries management agencies grew in personnel and resources in the 1980’s and 1990’s, the Tribes responded by engaging in efforts to reestablish coho within their ceded areas in the interior Columbia River basin.  In particular, the Yakama Nation has enacted coho reintroduction programs in the Yakima, Wenatchee and Methow rivers, as has the Nez Perce Tribe in the Clearwater River.  These programs were each initiated by acclimating and releasing juvenile coho, produced from a composite lower Columbia hatchery stock, back into upstream areas of these rivers in successive years.  As mature fish returned in-basin, some were allowed to escape upstream to the natural spawning areas, and others were collected for hatchery broodstock.  Progeny from the latter have been used for ongoing supplementation, progressively replacing the out-of-basin juveniles.  However, not only was the original stock of out-of-basin origin, it had also been subjected to well over 15 successive generations within in a segregated hatchery program, and could be considered as highly domesticated.  In light of concerns regarding potential deleterious effects of hatchery rearing on the natural fitness potential of a salmon stock, many would question whether the composite lower Columbia hatchery stock retained the genotypic and phenotypic capacity to successfully reestablish a naturally productive population.  Results from these reintroduction programs, however, indicate that the concerns are exaggerated.  In spite of negative domestication effects that may have accumulated within this coho stock, a portion of the reintroduced hatchery smolts not only returned as mature adults to these rivers, but they also successfully spawned, and their natural-origin progeny are returning in increasing numbers and produced a second and now third generation.  There have been dramatic increases in annual escapement to each of the subbasins.  There have also been dramatic increases in annual redd counts, as well as expansion in the range where spawning is occurring.  It would appear that any accumulated domestication effects within this out-of-basin hatchery stock is being reduced by the effects of broodstock management and by natural selective forces, creating populations of increasing natural productivity.