Effects of immobilization by electricity and MS-222 on brown trout broodstock and their progeny
To determine the effects of electrically and chemically induced immobilization on postspawn broodstock and their progeny, age‐2 and age‐3 female broodstock and age‐2 male broodstock of brown trout Salmo trutta were immobilized with electricity or tricaine methanesulfonate (MS‐222), stripped of their eggs or milt, and weighed. Eggs taken from electrically immobilized females were fertilized with milt taken from age‐2 males that were immobilized with electricity, and eggs taken from females immobilized with MS‐222 were fertilized with milt taken from age‐2 males that were immobilized with MS‐222. After spawning, the mortality and weight of broodstock were compared twice over a 6‐month period. Egg viability and growth of offspring fry from each treatment group were also compared. Electricity induced complete and consistent immobilization in brown trout broodstock. Electrically immobilized fish were more easily handled than fish immobilized with MS‐222; however, electrically immobilized fish survival (70%) was significantly less than fish immobilized with MS‐222 (83%). Broodstock growth differences were only noted at 6 months postexposure, when the mean weight of electrically immobilized fish was slightly less than the weight of fish immobilized with MS‐222. Broodstock immobilization by electricity did not reduce egg viability or fry growth.