Preference for Rocky Habitat by Age-0 Yellow Perch and Alewives

Abstract

We determined the preference for rocky versus sandy bottom of age-0 alewives ( Alosa pseudoharengus) and newly demersal age-0 yellow perch ( Perca flavescens). The catch rate of both species in gill nets at rocky sites was approximately four times greater than at sand sites along the Wisconsin shoreline during mid-August through mid-September 2002. For yellow perch the preference for rocky habitat was probably related to shelter and food; diet analysis showed that young perch from rocky habitat primarily consumed amphipods and isopods, prey associated with rocks. The reasons why alewives associate with rocky habitat are not obvious, but may be related to feeding on emerging insects. These results indicate that a preference for rocky habitat by yellow perch, noted earlier for larger and/or reproductive individuals, begins during their first summer. The results also indicate that assessments of age-0 yellow perch and alewife that sample only soft substrates may seriously underestimate abundance.