Effects of Stocking on Genetics of Wild Brook Trout Populations

Publisher Website
Google Scholar
Abstract
The long-term genetic impact of maintenance stocking upon wild brook trout (S. fontinalis) populations in Wisconsin [USA] was evaluated. Trout were collected from streams of the Wolf and Fox River drainages and from the Osceola State Trout Hatchery. The stocking histories of the streams ranged from unstocked to heavily stocked for many years. The planted fish consisted primarily of fingerling and catchable brook and brown trout (Salmo trutta). Blood plasma and whole-eye homogenate samples were analyzed electrophoretically for transferrin (Tf) and lactate dehydrogenase (Ldh-B2) systems. Esterase was monomorphic in all samples, but Tf and LDH displayed genetic polymorphism. The occurrence of several Tf A/A phenotypes among wild fish is notable because previous genetic studies considered the combination to be lethal. The hatchery stock was genetically distinct from most wild populations at both loci. Variation of Tf allelic frequencies among wild populations suggested an undisturbed natural geographic pattern. There were significant correlations between Ldh-B2 allelic frequencies and stream stocking histories, with the wild type allele decreasing in importance as stocking intensity increased. This relationship does not seem to reflect interbreeding between wild and hatchery trout. It may indicate alteration of selective pressures induced by ecological interactions between the 2 stocks.