Effects of Electroshock Voltage, Wave Form, and Pulse Rate on Survival of Cutthroat Trout Eggs

Abstract Eggs of cutthroat trout Oncorhynchus clarki were exposed for 10 s to continuous direct current (DC), pulsed DC (PDC) at 30 or 60 Hz, or the Coffelt Complex Pulse System (CPS®) wave form. Each treatment was conducted at 150 or 225 V. Treatments occurred every other day from fertilization to development of pigmentation in the eye. A different set of eggs (from the same pooled sample) was tested for each voltage-frequency level and day (i.e., eggs were treated only once). Percent mortality at eye-up of eggs exposed to 150 V PDC was no different from that of controls, whereas mortality of eggs exposed to 150 V DC was greater. Eggs exposed to PDC and DC at 225 V exhibited a significant increase in mortality when shocked on days 4–14 postfertilization. At the higher voltages, CPS also caused significant egg mortality. These results suggest that voltage level is more critical to egg survival than either wave form or pulse rate. If it is necessary to shock over redds, low voltages should be used regardle...