Effects of fish on stream perlids.

Abstract

Fish density is determined to have no significant impact on the density of Acroneuria sp. in a northern Michigan stream. Drift of upstream perlids may swamp the effects of predaceous fish. Perlids may be adequately adapted to avoid predators by feeding at night and by possessing cryptic coloration. Acroneuria sp. prefers cobble substrate because it is more stable and because it offers sufficient microrefugia. Perlid density may also be dependent upon current velocity. The findings here in combination with previous research suggest that multiple variables must be considered in determining whether predaceous fish can significantly influence benthic invertebrates.