Ruffe Gymnocephalus cernuus, a percid native to Europe and Asia, is established in the Lake Superior drainage and could have negative impacts on native fish through competition for forage and predation on fish eggs. We investigated the diet of ruffes in the 4,654-ha St. Louis River estuary in May-October 1989-1990 and the feeding periodicity of ruffes in two adjacent habitats during five 24-h periods in summers 1990-1991. Ruffes were primarily benthophagous. Age-0 ruffes fed mostly on cladocerans and copepods in early summer and midge larvae (Chironomidae) in late summer and fall. Adult ruffes less than 12 cm fed mostly on midges and other macrobenthos but also consumed large numbers of microcrustaceans. Adult ruffes 12 cm and larger fed mostly on midges, burrowing mayflies Hexagenia spp., and caddisflies (Trichoptera). Ruffes consumed few fish eggs. Adult ruffes in deeper waters and all age-0 ruffes fed throughout the day as indicated by weight patterns of stomach contents. However, adult ruffes generally moved to shallower waters at night to feed most heavily. Results of this study indicate that ruffes will probably compete with other benthic-feeding fishes such as yellow perch Perea flavescens and trout-perch Percopsis omiscomaycus.
|Original language||English (US)|
|Number of pages||14|
|Journal||Transactions of the American Fisheries Society|
|State||Published - May 1995|
Bibliographical noteFunding Information:
to genus and species. C. Bronte, P. Hudson, J. Jans-sen, and several anonymous referees critically reviewed this study and made helpful suggestions. Support was provided by the Minnesota Sea Grant College Program, Department of Commerce, under grant USDOC-NA86AA-D-SG112, Minnesota Agricultural Experiment Station under Project 72, National Biological Survey-Great Lakes Science Center, and Minnesota Department of Natural Re- sources. This is journal reprint JR323 of the Min-nesota Sea Grant College Program, paper 20,221 of the Minnesota Agricultural Experiment Station contribution series, and contribution 880 of the National Biological Service-Great Lakes Science Center.