INFORMATION-TRANSFER AND THE FACILITATION AND INHIBITION OF FEEDING IN A SCHOOLING FISH

Recent studies show that fish forage actively when perceived risk is low, but decrease foraging and increase vigilance when perceived risk is high. Isolated juvenile chum salmon, Oncorhynchus keta, were visually exposed to groups of conspecifics engaged in different activities to examine their ability to gain information about foraging opportunity and risk by interpreting conspecific behavior. Isolates ate most when exposed to feeding groups, less when exposed to nonfeeding groups, and least when exposed to alarmed groups. Isolates exposed to alarmed conspecifics also spent more time motionless than did fish exposed to either feeding or nonfeeding conspecifics. These findings indicate that schooling fish gain information by interpreting con-specific behavior, and are consistent with research showing that animals balance the conflicting demands of foraging and vigilance.