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Newman, R.M., D.H. Ogle, J.D. Trexel, and F.G. Henson, 1997. Trophic Relations
of Ruffe in North America: Concern for Interactions With Native Species, University of
Minnesota, Northland College
Proceedings of the International Symposium on Biology and Management of Ruffe, March
21-23, 1997
Trophic Relations of Ruffe in North America: Concern for Interactions
With Native Species
Abstract
Concern about the effects of the exotic ruffe (Gymnocephalus cernuus) on native
fishes in North America has largely centered on the ruffe's role as a predator of fish
eggs or as a competitor for limited benthic food resources. We review past and current
work on ruffe diet and food consumption in North America and discuss the potential for
ruffe to influence benthic food resources and native benthivores. Diet surveys in the
Duluth-Superior harbor indicate that young-of-the-year ruffe eat primarily benthic
microcrustaceans early in the summer, but include more macrobenthos later in the summer.
Age 1 and older ruffe feed predominantly on macrobenthos: chironomids, mayflies,
caddisflies and amphipods. Diet surveys in two more recently colonized tributaries to Lake
Superior confirm this general pattern. However, recent evidence suggests that ruffe are
selective feeders, consuming greater proportions of some taxa relative to their abundance
in the benthos. Selectivity differed among sites; however, the typical high occurrence of
chironomids in the diet does not generally appear to be due to strong positive selection
for chironomids. Ruffe daily rations in the Duluth-Superior harbor during July and August
1990 and 1991 ranged from 2-7% of wet body weight. Daily ration appeared lower in 1991
than 1990 and was associated with reduced densities of large macrobenthos (large
chironomids and caddisflies) in 1991. Comparisons of diet overlap with ruffe in the two
tributaries indicated high overlap with trout perch (Percopsis omiscomaycus), but
variable overlap with yellow perch (Perca flavescens). Mesocosm experiments with
ruffe and perch suggest that competition for benthic food resources is important.
Contact: Raymond M. Newman, Department of Fisheries and Wildlife,
University of Minnesota, St. Paul, MN 55108 or rmn@finsandfur.umn.edu
Keywords: Ruffe, Ecological_interactions, Predators
Product Type: Publications, Conference_proceedings
User Type: General
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