- University of Toronto
Empirically derived estimates of prey resources using conventional sampling methods are generally poor indices of actual food available to visually feeding benthivorous fish. We preferentially sampled the most active fraction of the benthos (presumably that most detectable by fish) utilizing short-term (4 d) colonization of artificial substrates, and used colonist biomass to explain temporal variation in stomach contents of bluegill sunfish (Lepomis macrochirus) in Lake Opinicon, Ontario. Simple linear regressions showed that total biomass of colonists explained 75% of the variance in the biomass of stomach contents. Independent variables using a limited taxonomic range or size range of colonists explained less variance in stomach contents. The convenience and simplicity of this methodology, and its ability to explain within-lake variation in food exploitation by visual benthivores, suggest that artificial substrate colonization could be useful for surveys of prey availability to benthivorous fishes.
The study was conducted in Lake Opinicon, Ontario, during the summers of 1984 and 1985. The littoral zone of this lake supports large resident populations of several widespread littoral fish species, with bluegill dominating in terms of abundance and biomass through most of the summer (Keast and Harker 1977; Keast 1978a,b, 1980). Keast et al. (1978) and Konkle (1988) describe the lake and the study sites.