FEEDING AND ORIENTATION OF MOTTLED SCULPIN, COTTUS-BAIRDI, TO WATER JETS

Mottled sculpin, Cottus bairdi, from Lake Michigan are primarily nocturnal feeders that use the mechanoreceptive lateral line system to locate prey. Signals from swimming and suspension feeding prey are due to rhythmic movements of the body and/or appendages which produce a current with a net water flow (DC) and a vibratory water flow component (AC) superimposed on it. To determine whether the feeding response of the mottled sculpin is elicited by AC and/or DC components, we tested the response of mottled sculpin to water jets which were either an unmodulated flow (DC) or had a superimposed modulated flow (AC: 10 and 20 Hz). Both free-roaming fish and fish that had been pre-positioned relative to the stimulus were tested. Results indicate that sculpins are more likely to bite at an AC jet nozzle and will bite at the jet nozzle at a greater distance for AC jets than for DC. However, fish can be conditioned to turn toward the DC flow. A fish trained to respond by turning toward a DC jet will nearly cease to respond to the DC jet after a few trials with an AC jet (which mainly elicit bites). The results suggest that there is an unconditioned bite response to AC signals and that training can produce a conditioned turn response to DC signals. © 1990 Kluwer Academic Publishers.