EFFECTS OF IMMOBILIZATION BY ELECTRICITY AND MS-222 ON BROWN TROUT BROODSTOCK AND THEIR PROGENY

To determine the effects of electrically and chemically induced immobi lization on postspawn broodstock and their progeny, age-2 and age-3 fe male 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 electr ically immobilized females were fertilized with milt taken from age-2 males that were immobilized with electricity, and eggs taken from fema les immobilized with MS-222 were fertilized with milt taken from age-2 males that were immobilized with MS-222. After spawning, the mortalit y and weight of broodstock were compared twice over a 6-month period. Egg viability and growth of offspring fry from each treatment group we re also compared. Electricity induced complete and consistent immobili zation in brown trout broodstock. Electrically immobilized fish were m ore easily handled than fish immobilized with MS-222; however, electri cally immobilized fish survival (70%) was significantly less than fish immobilized with MS-222 (83%). Broodstock growth differences were onl y noted at 6 months postexposure, when the mean weight of electrically immobilized fish was slightly less than the weight of fish immobilize d with MS-222. Broodstock immobilization by electricity did not reduce egg viability or fry growth.