Trout from above barriers in five remote streams were identified as rainbow trout with, in most cases, a slight cutthroat influence. Trout from below barriers were mostly rainbows except for the Escalante River where some cutthroat trout and two possible hybrids were found. Downstream specimens were probably juveniles of anadromous steelhead stocks. Although individuals from upstream and downstream populations could not be consistently separated morphologically, in three streams there were differences in the mean scale counts and the incidence of basibranchial teeth. Gonadal development of small (<200 mm) fish was the most obvious character distinguishing resident headwater populations from the anadromous downstream populations. Downstream populations were indistinguishable from each other electrophoretically, but upstream populations differed both from each other and from their respective downstream populations at least one electrophoretic locus. The management implications of our findings are discussed.
Parkinson, E., Behnk, R. J.; Pollard, W.. 1984. A Morphological and Electrophoretic Comparison of Rainbow Trout (Salmo gairdneri) Above and Below Barriers on Five Streams on Vancouver Island B.C.. Ministry of Environment. Fisheries Management Report. FMR83