Selective foraging in the white sucker (Catostomus commersoni)

The white sucker (Catostomus commersoni) is a widespread and often abundant North American species. This benthivore can play an important role in the ecology of both fish and benthic communities in lakes and streams. However, the feeding behaviour and ecology of the white sucker have received limite d study beyond a description of gut contents from small samples of fish. In this study, the diet of white suckers was determined in relation to season and depth distribution of the fish, as well as to the abundance and type o f zoobenthos sampled at the site of fish capture. Suckers fed predominantly on either zoobenthos or zooplankton, with some seasonal variation. They sp ecialized on particular prey and also on the largest individuals within the ir "speciality," thus exhibiting both resource partitioning and size-select ive predation. These findings demonstrate that white suckers can be extreme ly flexible in their use of resources as opposed to being simple generalist feeders. This attribute, plus their tolerance of a range of environmental conditions, partly explains the abundance of white suckers and their wide d istribution in temperate lakes and streams.