hatcheries the answer??? I think not!!>>>>REPRODUCTIVE SUCCESS OF HATCHERY AND WILD STEELHEAD
Hulet, P.L., Chris W.Wagemann, Cameron S. Sharpe, and Steven A. Leider.
1995. Studies of hatchery and wild steelhead in the lower Columbia
basin. Washington Dept. Fish and Wildlife. Progress Report for
fiscal year 1994. No. RAD. 95-03.
Posted by Bill Bakke
In 1986 a genetic marking study was begun to determine the relative reproductive success of hatchery and wild winter-run steelhead spawning in the Kalama River, Washington state, USA. This report presents< information from the ninth year of an eleven year study.
To briefly review, genetically marked hatchery winter-run smolts were released in 1987, 1988, and 1989. Fish from those releases that returned as 2-salt spawners potentially contributed to natural production in 1989, 1990, and 1991 broods of winter steelhead in the Kalama River.
This report presents genetic mark data from age 3 smolts of the 1991 brood, as well as the second estimate of reproductive success to the adult stage (based on data from 2-salt adults of the 1990 brood), for winter-run steelhead. The results are prliminary, as they are based on data from the predominate age class (2.1+), rather than all age classes that return from a brood year.
A key assumption in this study is that the genetic mark did not influence the survival of naturally produced offspring. This assumption is being tested and will be addressed in later reports.
Based on the data analysis, two key conclusions can be made. First, it is highly unlikely that HxW parents (hatchery fish crossed with wild fish) were as successful in producing adult offspring as were WxW production of adult offspring was not statistically distinguishable from zero, despite a large offspring sample size of 546.
Thus, while hatchery winter steelhead had the potential to produce 55% of the winter-run offspring, natural production by those hatchery fish appears to have been near zero, based on the 1990 brood age 2.1+ adults returning to the Kalama River during the 1993-1994 winter-run.
Although preliminary, the two years of adult winter-run steelhead data collected thus far indicate that the reporductive success differential between hatchery and wild winter-run steelhead are similar to that previously estimated for Kalama River summer-run steelhead.
In 1984 it was determined that hatchery winter-run have the potential to interbreed with wild winter as well as wild summer steelhead. Therefore, findings of low hatchery winter-run reproductive success have serious implications regarding the potential genetic effects that introgression of hatchery winter-run could have on wild populations.