Repeat Homing of Brown Trout (Salmo trutta) in Lake Eucumbene, New South Wales, Australia

Abstract

Spawning runs of lentic-dwelling brown trout (S. trutta) and rainbrow trout (S. gairdneri) in Swamp Creek, an inlet of Lake Eucumbene, were studied for 4 consecutive years, and 3517 browns and 415 rainbows were tagged during 1968-70. A further 240 browns and 229 rainbows were marked in other inlets. Recaptures of marked browns in 1969 and 1970 showed a high incidence of repeat homing, up to 25.7 and 10.6% returning after 12 and 24 mo., respectively. Few rainbrow trout homed. Tag loss and the mortality and maturation of marked browns were estimated and percentage homing and straying in 1969, 1970 and 1971 was calculated. High percentage homing (.gtoreq. 90%) in 1969-70 and the variance in external form in the lentic population suggested some genetic isolation within the brown trout population. Homing ability was not influenced by fish age. Percentage homing fell markedly in 1971 after the moval of nearly all resident brown trout from Swamp Creek and suggested racially distinct stream trout populations to be an important navigational cue to homing brown trout.