Development and Evaluation of Alternative Habitat Suitability Criteria for Brook Trout

Abstract

We developed habitat suitability criteria (HSC) for mean column velocity and depth from a foraging model (foraging-model HSC) that incorporated the energetic costs and benefits of a foraging location for drift-feeding brook trout Salvelinus fontinalis in Hunt Creek, Michigan. We compared these criteria to HSC developed from frequency-of-use data (use HSC) collected in Hunt Creek. Foraging-model HSC predicted that a single mean column velocity was optimal and depended on fish size, whereas a range of optimal mean column velocities was predicted from frequency-of-use data. The optimal velocities predicted from foraging-model HSC for yearling and older brook trout (range 32–49 cm·s−1) were greater than the highest optimal velocity (27 cm·s−1) predicted by use HSC. The optimal-velocity values predicted from foraging-model HSC for age-0 fish (23 and 29 cm·s−1 for 5- and 7.5-cm fish, respectively) were within the range of optimal velocities (6–30 cm·s−1) predicted from use HSC. The predicted range of usable velocities was narrower for foraging-model HSC than for use HSC, regardless of fish size. Foraging-model HSC values for depth were a function of current velocity and fish size and were similar to use HSC. Use HSC suitability scores for an independent set of habitat use observations in Hunt Creek were significantly higher than foraging-model HSC for age-0 fish but not for yearling and older fish. This may indicate that use HSC are too general and do not represent the actual suitability of foraging microhabitats in Hunt Creek. Yearling and older brook trout used microhabitats with higher mean column velocities and greater depths than age-0 fish.