Boldness and shyness were investigated as ‘personality’ traits in hatchery-reared rainbow trout Oncorhynchus mykiss. Bold fish spent more time in an open area and were more active than shy fish and these behaviours could be used as indicators of boldness and shyness. These differences were related to learning ability in a simple conditioning task. Bold fish learned the task more quickly than shy fish.
Sneddon, L. U. (2003). The bold and the shy: individual differences in rainbow trout. Journal of Fish Biology, 62(4), 971-975.