The response of littoral invertebrate populations to exclusion of fish (principally small bluegill sunfish, Lepomis macrochirus) from allochthonous detritus habitats in Bays Mountain Lake, Sullivan County, Tennessee, was monitored from mid-March until mid-June 1980. The following taxa reached densities within fish exclosures that were significantly higher than those in control nets on at least one occasion: Alona, Chydorus, and Eurycercus (Cladocera: Chydoridae); cyclopoid copepods; non-predaceous midges (Chironominae and Orthocladinae) and predaceous midges (Ceratopogonidae and Tanypodinae). Evidence for the direct effect of fish predation on prey densities was most convincing for Chydorus during their "spring crash" in early April, Eurycercus during a less dramatic decline in late April to early May, and for non-predaceous midges after three months of fish exclusion in mid-June. Each of these taxa was an important component of the diet of small bluegill sunfish during the relevant time periods.