Electronarcosis, the immobilization of a fish after an electric current has been applied and discontinued, is a potential alternative to chemical anesthetics. Successful narcosis was defined as the immobilization of a fish for 1-15 min without causing physical damage. In the laboratory, AC successfully narcotized juvenile (13-19-cm standard length, SL) northern pike (Esox lucius) at selected voltages; however, AC voltages that produced narcosis or resulted in physical damage were variable and unpredictable. In contrast, 60-90-V pulsed DC (PDC) for 10-60 s successfully narcotized juvenile pike without inducing physical damage. Duration of narcosis was directly related to voltage and inversely related to fish length. In the hatchery, sexually mature northern pike (45-97 cm SL), collected from the Mississippi River, were successfully narcotized by 60-V PDC for 10 s. Duration of narcosis was unrelated to fish length or sex, and averaged 58 plus or minus 7 s (mean plus or minus SE). This allowed sufficient time to collect eggs or milt. All fish were swimming upright within 3 min after treatment, and no mortalities were observed over the next 24 h. Survival of eggs from fertilization to eye- up did not significantly differ between eggs collected from electronarcotized adults and adults anesthetized with MS-222 (tricaine methanesulfonate). Electronarcosis represents a possible alternative to chemical anesthetics for immobilizing northern pike broodstock without an apparent impact on egg survival.
