Induced Mortality and Sublethal Injuries in Embryonic Brook Trout from Pulsed DC Electroshocking

Abstract

Despite heightened concern for potential adverse effects of electrofishing on fish, little information is available on the effects of electrofishing on juvenile fish. The purpose of our study was to determine if electrofishing impairs the survival and development of embryonic brook trout Salvelinus fontinalis. Brook trout embryos, both uncovered and buried in an artificial redd, were electroshocked at 21 d postfertilization (pre-eyed). Uncovered embryos also were electroshocked at 37 d postfertilization (eyed). When electroshocked, pre-eyed embryos suffered greater embryo mortality (85%) and incidence of hatchling morphological anomalies (22%) than unshocked embryos (14% and 7%, respectively), whereas hatching times and hatchling weights were similar between groups. Emergence from electroshocked pre-eyed embryos also was significantly lower (23%) than from unshocked embryos (67%), and the mean time at which fish emerged was longer for shocked embryos (88 d) than for unshocked embryos (85 d). Survival and development of electroshocked eyed embryos were not affected. Our results demonstrate the potential of electrofishing to impair development of brook trout embryos through sublethal and lethal effects.