Learning for angling: an advanced learning capability for avoidance of angling gear in red sea bream juveniles

Abstract

Angling has been the cause of mortality for fish since ancient. The avoidance learning for angling gear could be considered as a survival strategy against the mortality by angling. Whereas some studies indicated the possibility of avoidance learning for angling gear, most studies investigated the avoidance learning by using groups of fish, in which it is difficult to reveal the process and mechanisms of the learning. The present study elucidated the avoidance learning for angling gear by experiment of single fish in a tank using red sea bream Pagrus major juveniles. Individuals with only once or twice of experience for angling avoided angling gear while showing the feeding motivation for pellets, representing avoidance learning for the angling gear. Most of the experienced individuals avoided the krill attached with a fishing line, but not krill and pellets near the angling gear. Feeding rate for prey on a fishing line at two month after the angling trial demonstrated that approximately half of fish kept the memory for angling gear. A series of experiment for angling gear elucidated that red sea bream juveniles are equipped with considerable learning capability for angling gear, suggesting a cognitive evolution for angling.