Behavioral tests for magnetic sensitivity of hime salmon (Kokanee: land-locked sockeye salmon Oncorhynchus nerka)

Abstract

Juvenile and mature hime salmon were tested for their magnetic sensitivity using a successive conditioning. Fifty juvenile fish were reinforced according to concurrent changes of intensity, direction, and inclination of the magnetic field as a conditioned stimulus and an electric shock as an unconditioned stimulus. Twenty mature fish were reinforced according to an alternative magnetic field which rotates the horizontal component of the magnetic field in the tank through 120° at 1 Hz. The intensity of the total magnetic field in the tank was also changed from 0.56 to 0.80 gauss. Cumulative number of training reached 300 times for juvenile fish and 600 times for mature fish. No statistically significant conditioned reflex was observed in either juvenile or mature fish. However, the other fifty juvenile fish and twenty mature fish were successfully conditioned by lighting stimulus (100-130 lx for juvenile fish and 20-25 lx for mature fish) instead of the magnetic stimulus. These results indicate that hime salmon may not have magnetic sensitivity.