Hunger, light level and body size affect refuge use by post‐settlement lingcod Ophiodon elongatus

Abstract

Using experimental methods, body size, nutritional state (hunger) and light level were investigated as possible determinants of the extent to which juvenile lingcod Ophiodon elongatus used structural refuges. In the laboratory, older, larger individuals (134–162 mm total length, LT) exhibited a higher propensity for structure use than did smaller juvenile fish (78–103 mm LT). In fish of both body sizes, increasing hunger levels caused fish to emerge more readily from refuges than satiated individuals, with this effect most prominent for smaller fish. Diel patterns of ambient illumination were simulated in the laboratory, and refuge use by large individuals decreased significantly in response to lower nocturnal light levels, a pattern that was not observed in the smaller size class. These results indicate an ontogenetic shift in refuge use. During the summer, as post‐settlement fish grew larger, they tended to increase affinity for structurally complex habitat, and also showed divergent patterns of behaviour in relation to hunger and light level.