Operant conditioning of feeding behaviour and patterns of feeding in thick lipped mullet, Crenimugil labrosus (Risso) and common carp, Cyprinus carpio (L.)

Groups of carp and thick lipped mullet quickly learned to operate an underwater trigger for food reward. Single mullet also learned this operant response but single carp did not. Groups of mullet exhibited a higher rate of responding than groups of carp. Mullet appeared to feed in bouts, whereas carp fed randomly during the learning trials. Both species adapted well to six days continuous demand feeding. Grouped and single mullet decreased their feeding at night but carp did not show a diurnal feeding pattern. Feeding responses were found not to be sequences of random events and response rates over the six days were higher in carp than in mullet. In both species, individual fish within a group operated the trigger significantly more often than other fish but all fish took food and gained weight.