Social Hierarchy, Territoriality, and Stress Reactions in Sunfish

Abstract

Twenty-five groups of 4 sunfish [Lepomis gibbosus] were investigated for aggressive actions. A hierarchy was found for each of the groups. Size and sex were both important in determining the makeup of the hierarchy, with larger fish and males tending to be dominant. The fish were not highly territorial, but some territorial behavior was observed in 10 of the 25 groups. Investigation of stress reactions centered around 3 possible morphological adaptations: spleen weight, total body weight and quantity of interrenal tissue. The 1st 2 showed no correlation with the social rank of the fish. The quantity of interrenal tissue was correlated with the number of aggressive actions initiated by each fish, with a correlation coefficient of -0.466, which is significant.