ABSTRACT
Allozyme genetic marking approaches were used in two long-term studies to estimate the reproductive success of non-locally derived stocks of hatchery summer and hatchery winter steelhead spawning naturally in the Kalama River. Results of the winter-run study corroborate those previously published from the summer-run study. Reproductive success (offspring produced per spawner) of the hatchery steelhead was substantially lower than that of the wild fish. Also, the disparity in reproductive success was increasingly pronounced at successive (subyearling, smolt, and adult) life history stages of the offspring. These results are believed to reflect genetic differences between the wild and non-local hatchery stocks. Because their natural spawning poses genetic and ecological risks to wild steelhead, the non-local hatchery adults are no longer permitted access to principal wild Kalama steelhead spawning areas. Moreover, new research has been initiated to assess the wild stock conservation merits of using locally derived wild broodstock as a source for hatchery steelhead production. Specifically, the reproductive success of hatchery-reared steelhead spawned from wild Kalama summer-run broodstock will be compared to that of their wild-reared counterparts by relating microsatellite DNA profiles of naturally produced offspring to those of their prospective hatchery and wild parents.