Relationship between natural productivity and the frequency of wild fish in mixed spawning populations of wild and hatchery steelhead (Oncorhynchus mykiss)
M.W.
Chilcote-2003
Canadian Journal of Fisheries and Aquatic Sciences, 60(9): 1057-1067
Abstract:
The
proportion of wild fish in 12 mixed populations of hatchery and wild
steelhead (Oncorhynchus mykiss) was evaluated for its relationship to
mean and intrinsic measures of population productivity. The population mean
of ln(recruits/spawner) was used to represent mean productivity. Intrinsic
productivity was represented by values for the Ricker a parameter as
estimated from fits of spawner and recruit data. Significant regressions (p
< 0.001) were found between both measures of productivity and the
proportion of wild fish in the spawning population (Pw).
The slopes of the two regressions were not significantly different (p
= 0.55) and defined a relationship suggesting that a spawning population
comprised of equal numbers of hatchery and wild fish would produce 63% fewer
recruits per spawner than one comprised entirely of wild fish. Study
findings were not sensitive to likely levels of data error or confounded by
extraneous habitat correlation with Pw. Population status
assessments and conservation monitoring efforts should include Pw
as a critical variable. For natural populations, removal rather than
addition of hatchery fish may be the most effective strategy to improve
productivity and resilience.
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