Sensory deficits induced by cadmium in banded kokopu, Galaxias fasciatus, juveniles

The potential for cadmium to produce sensory deficits in the mechanosensory lateral line and olfactory systems was examined in migratory Galaxias fasc iatus juveniles or 'whitebait'. Using a two-choice chamber apparatus, three groups of whitebait were tested for a known attraction to adult pheromones and then exposed to either 0.1, 0.5 or 1 mug Cd+2 l(-1) for 48 h and retes ted. The attraction to adult pheromones had been eliminated after exposure to concentrations of 0.5 and 1 mug Cd+2 l(-1), indicating these levels of c admium exposure had impaired olfactory function. Rheotaxis trials were cond ucted to determine the level of cadmium exposure which would inhibit latera l line function. The lateral line system was not blocked until a concentrat ion of 2 mug Cd+2 l(-1). The blocking of the lateral line and olfactory sen sory systems was reversible. After 14 days recovery in clean freshwater bot h rheotaxis and the attraction to adult pheromones had returned. Whitebait were also tested for a preference/avoidance response at 2 mug Cd+2 l(-1). F ish showed neither a preference for, or an avoidance of, a concentration wh ich would disable both the lateral line and olfactory sensory systems. The disabling of these sensory systems may render migratory cues undetectable, affecting habitat selection by whitebait, which may ultimately affect the d istribution of banded kokopu populations.