Effects of varying voltage and pulse pattern during electrical immobilization of adult chum salmon on egg survival to the eyed egg stage

Electrical shock is becoming widely used to immobilize adult salmon before gamete removal. Working with immobilized fish reduces repetitive motion inj uries among workers and decreases staff requirements, but survival rates of eggs obtained from adults immobilized by electrical currents have varied. Eleven DC wave forms and voltage combinations were used to immobilize adult chum salmon Oncorhynchus keta, and survival rates of eggs taken from shock ed fish were compared with survival rates from fish immobilized with carbon dioxide. Egg survival rates increased as voltage and pulse pattern intensi ty decreased. Similar egg survival rates were recorded for those obtained f rom the carbon dioxide controls (98%) and those obtained at the lower volta ge and pulse patterns (96-98%), thus validating the use of electrical immob ilization on adult chum salmon before gamete removal.