Mechanisms Underlying Habitat Use of Juvenile Largemouth Bass and Smallmouth Bass

Abstract

Differences in habitat use between adult largemouth bass Micropterus salmoides and adult smallmouth bass M. dolomieu have been well documented, with largemouth bass occupying vegetated habitats and smallmouth bass occupying areas with cobble substrate. However, less is known about the habitat use of juveniles. Direct observations of three co-occurring populations of largemouth bass and smallmouth bass in New York State indicated that habitat use by age-0 fish was very similar to that of adults. To examine potential mechanisms underlying this pattern of habitat use, we conducted a pair of laboratory experiments. The first experiment, concerned with habitat-specific feeding rates, found that juvenile largemouth bass consumed aquatic insects at equal rates in vegetated and cobble habitats. In contrast, smallmouth bass fed at higher rates in cobble than in vegetation. The second experiment, which examined habitat-specific predation risk, found qualitative differences between the two species. Largemouth bass were more vulnerable to predation in cobble than in vegetation, whereas the predation vulnerability of smallmouth bass was higher in vegetation than in cobble. Together, the two laboratory experiments suggest differences between juvenile largemouth bass and smallmouth bass that may underlie the observed specialization for different habitats.