The effect of early experience on aggression in two territorial scorpaenid fishes

Abstract

The impact of population density and shelter availability on the development of aggressive behavior in two species of rockfishes, the black and yellow rockfish, Sebastes chrysomelas, and the gopher rockfish, Sebastes carnatus, were examined in this study. Adults of these species are typically territorial though other patterns of space utilization are observed. Dominance does not appear to account for these patterns. Since the level of aggressiveness seems to vary between groups, differences in early experience might play a role in determining adult behavior patterns. Laboratory experiments were performed on juveniles captured prior to settlement in which the aggressive tendencies of individuals were assessed by focusing on the development of displays toward a mirror image over a six month period. The results of this study suggest that the repertoire of agonistic behaviors used by adults is available to juveniles though seldom seen in the field. Increased population density and the availability of a shelter increase aggressiveness in S. carnatus and the effects of density were not reversible over the course of the experiment. The behavior of S. chrysomelas was less influenced by the manipulations.