Transferability of habitat suitability criteria for fishes in warmwater streams

We developed habitat suitability criteria and tested their transferability for nine fishes inhabiting unregulated Piedmont and Coastal Plain streams in Alabama. Criteria for optimal habitat were defined as those ranges of depth, velocity, substrate type, and cover type for which a species' suitability index (proportional abundance divided by proportional habitat availability, scaled from 0 to I) equalled or exceeded 0.4. We evaluated the transferability of criteria between study sites by testing the null hypothesis that species occurrence in a sample was independent of whether or not the sample was taken in optimal habitat. We also tested criteria transference to a large, flow‐regulated river sampled during low‐flow periods. Depth, velocity, and most substrate criteria developed for the bronze darter Percina palmaris successfully transferred between unregulated streams and to the flow‐regulated river samples. All criteria developed for a pair of closely related, allopatric darter species. the newly described lipstick darter Etheostoma chuckwachatte and the greenbreast darter E. jordani, transferred successfully when applied between species (in the unregulated sites) and to the regulated river samples. In contrast, criteria for the Alabama shiner Cyprinella callistia failed nearly all tests of transferability. Criteria for the speckled darter E. stigmaeum, the blackbanded darter P. nigrofasciata, an undescribed Percina species, and a pair of related, allopatric Cyprinella species transferred inconsistently. The species with good criteria transference had high suitability indices for the shallow depths. fast current velocities. and coarse substrates characteristic of riffle species. We suggest that microhabitat criteria for riffle fishes are more likely to provide a transferable measure of habitat quality than criteria for fishes that, although restricted to fluvial habitats, commonly occupy a variety of pool and riffle habitats.