Evaluation of Electronarcosis as a Tool for Collection of Biological Data from Adult Steelhead

We evaluated electronarcosis (EN) as an alternative to traditional techniques for immobilizing adult steelhead Oncorhynchus mykiss during trapping efforts designed to collect broodstock for hatchery operations and while gathering data for a variety of management and research activities. We compared the rates of fish injury, adult prespawn mortality, embryo survival, and spawner handling efficiency between EN and standard operating procedures with and without chemical anesthetics. Similar rates of injury occurred in adult steelhead when EN and tricaine methanesulfonate (MS-222) were used to immobilize fish. Similar rates of mortality were observed for developing embryos from parents treated with EN or MS-222. In comparisons between EN and a V-trough (VT) without anesthetic, the use of an EN chamber allowed for scale sampling procedures to be completed faster than when VTs were used. Fish sex and handling treatment contributed significantly to the models describing survival distribution of steelhead handled using EN or VT without anesthetic. A lower mortality rate was observed in females treated with EN than in females subjected to the VT treatment. These data support the further use and evaluation of EN for steelhead when collecting data, biological samples, or broodstock in field or hatchery settings.