Electrofishing Injury and Short-Term Mortality in Hatchery-Reared Rainbow Trout Stocked into an Ozark Stream

Abstract

We conducted an electrofishing injury study to evaluate potential effects of sampling procedures on survival and health of hatchery rainbow trout Oncorhynchus mykiss (187–307 mm total length) stocked into an Ozark stream. We assessed two groups of trout: one group had acclimated to stream conditions for 1 month; the other group was handled and transported just before the study. Each group was sampled by electrofishing (boat-mounted, 60-Hz AC) and seining (controls), resulting in four treatment groups (N = 21). We held fish for 48 h to evaluate mortalities in that period, then euthanized all fish and examined them for hemorrhages and spinal damage. No fish died during the 48-h holding period, indicating that our procedures did not cause significant sampling-related mortality among stocked trout in Brush Creek. Spinal damage was observed in 5% of fish collected with electrofishing but in none of the control fish. We found hemorrhages in 90% of electrofished trout but none in control fish, and recently handled and hauled trout had a greater occurrence and severity of hemorrhaging.