Social interaction in juvenile channel catfish

Social interactions between 11 pairs of channel catfish (Ictalurus punctatus) were observed and discrete behavioral units were described and analyzed. Dominant fish engaged regularly in aggressive activities and never in submissive activities, whereas subordinate fish were observed in submissive activities on a regular basis and rarely in those that were aggressive. Activity levels were significantly higher in dominant fish. There was no significant difference in activity levels between pairs equal and unequal in size. A factor analysis indicated three motivational systems underlying the social behavior in juveniles and two behaviors, which appeared as displacement activities, were functioning in agonistic encounters. Plasma cortisol concentrations measured in singletons, pairs, and individuals from a control tank suggested that the least amount of stress occurred in fish that were not interacting with any other individuals. Cortisol levels, however, were below those associated with stress in all the test fish.