Food and Habitat Partitioning Between Rock Bass (Ambloplites rupestris) and Smallmouth Bass (Micropterus dolomieui) Young of the Year

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Abstract
Young‐of‐the‐year rock bass and smallmouth bass were studied in 1977 along the west shore of Grand Island in the upper Niagara River, New York. Fish were collected every 2 weeks by shore scining. The average summer growth rate of smallmouth bass was 1.15 mm/day and of rock bass, 0.51 mm/day. Population estimates and laboratory habitat preference studies indicated that smallmouth bass preferred a rocky substrate whereas rock bass preferred a heavily vegetated substrate. Smallmouth bass less than 40 mm in total length (TL) fed mainly on zooplankton, chironomid larvae, mayfly nymphs, and amphipods, and when greater than 40 mm TL fed on amphipods, adult caddis flies, and small fish. Rock bass young of the year of all sizes fed on amphipods, copepods, and several other aquatic invertebrates. Levinsˈ average niche breadth or dietary diversity value for smallmouth bass was 2.51, and for rock bass, 3.78. Levinsˈ dietary overlap values were highest early in the season, 0.71–0.88, and decreased to 0.05–0.17 as the season progressed. Ecological segregation was by both food and habitat partitioning.
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