Gymnocephalus cernua
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Gymnocephalus cernua (Linnaeus, 1758)

Common name: Ruffe

Synonyms and Other Names: Eurasian ruffe, blacktail, pope, redfin darter, river ruffe, Acerina cernua, Gymnocephalus cernuus

Taxonomy: available through www.itis.govITIS logo

Identification: The ruffe is a small fish, reaching 10 inches in length, is olive-brown to golden-brown on its back with yellowish white undersides. Its fused dorsal fins are characterized by 12–19 dorsal spines followed by 11–16 soft dorsal rays. The caudal fin has 16–17 rays. Distinguishing characteristics were provided by Wheeler (1969, 1978), Maitland (1977), Page and Burr (1991), McLean (1993), and Stepien et al. (1998). Detailed traits and an identification key to members of the genus were given by Holcik and Hensel (1974). Name given by some authors is Acerina cernua (e.g., Berg 1949), also Gymnocephalus cernuus (e.g., Page and Burr 1991).

Size: 25 cm

Native Range:
Northern Europe and Asia (Berg 1949; Holcik and Hensel 1974; Wheeler 1978; Page and Burr 1991).
US auto-generated map Legend USGS Logo
Alaska auto-generated map
Hawaii auto-generated map
Caribbean auto-generated map
Puerto Rico &
Virgin Islands
Guam auto-generated map
Guam Saipan
Interactive maps: Point Distribution Maps

Nonindigenous Occurrences: The ruffe was first identified by Wisconsin DNR in specimens collected from the St. Louis River at the border of Minnesota and Wisconsin in 1987 (Pratt 1988; Pratt et al. 1992; Czypinski et al. 1999, 2000, 2001, 2003). Following that report, reexamination of archived samples revealed misidentified larval specimens of ruffe had been collected from the same area in 1986 (Pratt 1988). The ruffe subsequently spread into Duluth Harbor in Lake Superior and several tributaries of the lake (Underhill 1989; Czypinski et al. 1999, 2000, 2004; Scheidegger, pers. comm.; J. Slade, pers. comm.). It is found in the Amnicon, Flag, Iron, Middle, Raspberry, and Bad rivers, Chequamegon Bay, and Apostle Islands National Lakeshore in Wisconsin (Czypinski et al. 1999, 2000, 2001, 2003, 2004; Tilmant 1999).  In August 1994, it was found in Saxon Harbor, Wisconsin, and in the upper peninsula of Michigan at the mouths of the Black and Ontonagon rivers (K. Kindt, pers. comm.). In the lower Peninsula of Michigan along Lake Huron, the first three specimens were caught at the mouth of the Thunder Bay River in August 1995 (K. Kindt, pers. comm.). This species has also been collected in Michigan in Lake Michigan, Lake Superior, Torch Lake, Little Bay de Noc in Escanaba, Big Bay de Noc, Misery River, Ontonagon River, Thunder Bay, and Sturgeon River Sloughs (Czypinski et al. 1999, 2000, 2001, 2003, 2004; A. Bowen, pers. comm.; Pearce, pers. comm.; Zorn, pers. comm.).  The ruffe has been collected in Lake Superior at Thunder Bay Harbour, Ontario, Canada (Czypinski et al. 1999, 2000, 2001, 2004, 2007).

Ecology: The diet of ruffe changes throughout the course of development, becoming more benthic in nature with increasing size (Ogle et al. 2004). Copepoda, Daphnia spp., and Bosmina longirostrus dominated the overall diet of larval ruffe in the St. Louis Harbor (Ogle et al. 2004). Chironomids and the bottom-dwelling larvae of other insects, mainly mayflies and stoneflies, were frequently consumed in fresh water and, with increasing body size, became increasingly important in the diet of ruffe (Hölker and Thiel 1998). In laboratory experiments, Fullerton et al. (1998) found that ruffe preferred soft-bodied macroinvertebrates. Histological examination of ruffe from the Duluth-Superior Harbor population revealed that the spawning period extended from late April through mid-June in 1994 (Leino et al. 1997). Ruffe is often associated with bottom waters and can tolerate lacustrine and lotic systems and depths to 85 m (Sandlund et al. 1985). The species' intolerance to deeper waters may limit its range of potential suitable habitat to Lake Erie, southern Lake Michigan, and shallow waters of the other Great Lakes (U.S. EPA 2008).

Means of Introduction: The ruffe was probably introduced via ship ballast water discharged from a vessel arriving from a Eurasian port, possibly as early as 1982-1983 (Simon and Vondruska 1991; Ruffe Task Force 1992). Within the Great Lakes, the species' spread may have been augmented by intra-lake shipping transport (Pratt et al. 1992; Stepien et al. 1998). Recent genetic research has indicated that the origin of ruffe introduced to the Great Lakes was southern Europe, not the Baltic Sea as previously believed (Stepien et al. 1998).

Status: The ruffe has already invaded Lake Superior and GARP modeling predicts it will find suitable habitat almost everywhere in all five Great lakes. GARP models are not able to make a prediction about some of the deeper waters of Lake Superior (U.S. EPA 2008). It has been established in western portion of Lake Superior since about 1988 and expanded in an easterly direction. Ruffe has been reported from Lake Huron at Thunder Bay River, and in Thunder Bay, Lake Superior, Ontario, Canada. It has become the dominant species in the St. Louis River estuary (McLean 1993) and considered the most abundant of the 60 species found in Duluth Harbor (Ruffe Task Force 1992). Based on bottom trawl samples, ruffe makes up an estimated 80% of fish abundances in the southwestern regions of Lake Superior (Leigh 1998). The population in Duluth Harbor was estimated at two million adult fish in 1991 (Ruffe Task Force 1992). In 2006 surveys of Lake Huron, no ruffe were collected from Thunder Bay River and St. Marys River (Czypinski et al. 2007). In fact, ruffe has not been collected in the Thunder Bay region of Lake Huron since 2003 despite sampling efforts nor has it been found elsewhere in the lake (A. Bowen, pers. comm.).

Impact of Introduction: The ruffe has affected fish populations in other areas where introduced. In Scotland, native perch populations declined, and in Russia whitefish numbers have declined because of egg predation by ruffe (McLean 1993). Ruffe exhibits rapid growth and high reproductive output, and adapt to a wide range of habitat types (McLean 1993); therefore the species may pose a threat to native North American fish. Yellow perch Perca flavescens, emerald shiners Notropis atherinoides, and trout-perch Percopsis omiscomaycus have all declined since the introduction of this fish, although the association is not clear (McLean 1993). There is much concern that ruffe may have a detrimental effect on more desirable species in Lake Superior, such as yellow perch and walleye, by feeding on the young of these species (Raloff 1992), or by competing for food (McLean 1993). Savino and Kolar (1996) conducted a laboratory study to test for competition for food between ruffe and yellow perch. They found that competition could occur between the two species but that the outcome would not always be clear. Each species exhibited competitive advantages and disadvantages. Ogle et al. (1995) studied the diet of introduced ruffe inhabiting the St. Louis estuary. Their findings indicated that the species prey heavily on benthic insects thereby suggesting that ruffe compete for food with yellow perch, trout-perch, and other native benthic-feeding fishes. Fullerton et al. (1998) also observed that similarities in dietary preferences and in feeding rates of ruffe and yellow perch suggest a strong possibility for interspecific competition. Ruffe hold an advantage over native perch in their ability to better select moving objects under relatively dim light conditions or at high turbidity. Kolar et al. (2002) found that in a laboratory setting, ruffe exhibited higher consumption rates of benthic invertebrates than yellow perch in darkness over bare cobble and complex substrates. Ruffe has a very sensitive lateral line system and night adapted vision, and is more adapted to foraging under poor light conditions that yellow perch (Hölker and Thiel 1998). In a study of ruffe predation by native pike, bass, bullhead, walleye, and perch, Mayo et al. (1998) found that though ruffe comprised 71-88% of prey species biomass, all five of the selected predators ate ruffe at lower proportions, preferentially selecting native fish species.

Remarks: The ruffe also has been collected in the Canadian waters of Lake Superior at Thunder Bay and in Kaministiquia River estuary, 290 kilometers northeast of Duluth. Seven fish were collected from the latter location in 1991 (Ruffe Task Force 1992). Busiahn (1993) indicated that the potential North American range of ruffe may well extend from the Great Plains to the eastern seaboard and north into Canada. However, early reports that the ruffe was established in Lake Michigan (e.g., Page and Burr 1991) are considered erroneous. In March 1997, an international symposium was held in Ann Arbor, Michigan, to exchange information on the biology and management of ruffe (Jensen 1997). Ogle et al. (1996) found that certain native species preyed on introduced ruffe; however, their study indicated that predation is unlikely to effectively prevent ruffe from colonizing new areas in the Great Lakes.

Brazner et al. (1998) found that densely vegetated shoreline wetland habitats provide a refuge from intense competition with ruffe for indigenous fish.

Since the last ITIS update and 2004 American Fisheries Society names list update, there has been a return to the original species epithet (cernua). Authorities such as Eschmeyer's Catalog of Fishes (30 Sept. 2011 update), the Peterson fish guide, have FishBase reflect this change. According to W. Eschmeyer (pers. comm.), "cernua" is a noun and so does not decline (i.e., not an adjective to match the masculine genus). The ITIS expert for this species also confirmed the valid species name is now G. cernua (W. Starnes pers. comm.), although ITIS has yet to reflect that change.

References: (click for full references)

Berg, L.S. 1949. Freshwater fishes of the U.S.S.R. and adjacent countries, 4th edition. Three volumes. Translated from Russian, 1962-1965, for the Smithsonian Institution and the National Science Foundation, by Israel Program for Scientific Translations, Jerusalem, Israel. Volume 1:504 pp.; volume 2:496 pp.; volume 3:510 pp.

Boogaard, M.A., T.D. Bills, and D.A. Johnson. 2003. Acute toxicity of TFM and a TFM/niclosamide mixture to selected species of fish, including lake sturgeon (Acipenser fulvescens) and Mudpuppies (Necturus maculosus), in Laboratory and Field Exposures. Journal of Great Lakes Research 29(Supplement 1):529-541.

Boogaard, M.A., T.D. Bills, J.H. Selgeby, and D.A. Johnson. 1996. Evaluation of piscicides for control of ruffe. North American Journal of Fisheries Management 16(3):600-607.

Bowen, A. – U.S. Fish and Wildlife Service, Alpena Fish and Wildlife Conservation Office, Alpena, Michigan.

Brazner, J.C., D.K. Tanner, D.A. Jensen, and A. Lemke. 1998. Relative abundance and distribution of ruffe (Gymnocephalus cernuus) in a Lake Superior coastal wetland fish assemblage. Journal of Great Lakes Research 24 (2): 293-303.

Bronte, C.R., L.M. Evrard, W.P. Brown, K.R. Mayo, and A.J. Edwards. 1998. Fish community changes in the St. Louis River estuary, Lake Superior, 1989-1996: is it ruffe or population dynamics? Journal of Great Lakes Research 24(2):309-318.

Busiahn, T. R. 1993. Can the ruffe be contained before it becomes your problem. Fisheries 18(8):22-23.

Clearwater, S.J., C.W. Hickey, and M.L. Martin. 2008. Overview of potential piscicides and molluscicides for controlling aquatic pest species in New Zealand. Science & Technical Publishing, New Zealand Department of Conservation, Wellington, New Zealand.

Czypinski, G.D., A.K. Bowen, M.A. Goehle, and B. Brownson. 2007. Surveillance for ruffe in the Great Lakes, 2006. U.S. Fish and Wildlife Service. 19 pp.

Czypinski, G.D., A.K. Bowen, M.A. Goehle, S. Cogswell, and B. MacKay. 2004. Surveillance for ruffe in the Great Lakes, 2003. U.S. Fish and Wildlife Service. 41 pp.

Czypinski, G.D., A.K. Bowen, M.P. Sowinski, and B. MacKay. 2003. Surveillance for ruffe in the Great Lakes, 2002. U.S. Fish and Wildlife Service. 35 pp.

Czypinski, G.D., A.K. Hintz, S.M. Keppner, and E. Paleczny. 1999. Surveillance for ruffe in the Great Lakes, 1998. U.S. Fish and Wildlife Service, Ashland, WI.

Czypinski, G.D., A.K. Hintz, M.T. Weimer, and A. Dextrase. 2000. Surveillance for ruffe in the Great Lakes, 1999. U.S. Fish and Wildlife Service, Ashland, WI. 29 pp.

Czypinski, G.D., A.K. Hintz, M.T. Weimer, and A. Dextrase. 2001. Surveillance for ruffe in the Great Lakes, 2000. U.S. Fish and Wildlife Service, Ashland, WI. 32 pp.

Dawson, V.K., T.D. Bills, and M.A. Boogaard. 1998. Avoidance behavior of ruffe exposed to selected formulations of piscicides. Journal of Great Lakes Research 24(2):343-350.

Eschmeyer, W. - California Academy of Sciences, San Francisco, California.

Fullerton, A.H., G.A. Lamberti, D.M. Lodge, and M.B. Berg. 1998. Prey preferences of Eurasian ruffe and yellow perch: comparison of laboratory results with composition of Great Lakes benthos. Journal of Great Lakes Research 24(2):319-328.

GLMRIS. 2012. Appendix C: Inventory of Available Controls for Aquatic Nuisance Species of Concern, Chicago Area Waterway System. U.S. Army Corps of Engineers.

Gorman, O.T., M.P. Ebener, M.R. Vinson (eds.). 2010. The state of Lake Superior in 2005. Great Lakes Fishery Commission Special Publication 10-01.

Holcik, J., and K. Hensel. 1974. A new species of Gymnocephalus (Pisces: Percidae) from the Danube, with remarks on the genus. Copeia 2: 471-486.

Hölker F., and R. Thiel. 1998. Biology of ruffe (Gymnocephalus cernuus (L.)): A review of selected aspects from European literature. Journal of Great Lakes Research 24(2):186-204.

Jensen, D.A., editor. 1997. International symposium on biology and management of ruffe: symposium abstracts. (March 21-23, 1997, Ann Arbor, Michigan). Minnesota Sea Grant Publication X48.

Kindt, K. - U.S. Fish and Wildlife Service, Fishery Resources Office, Ashland, Wisconsin.

Kolar, C.S., A.H. Fullerton, K.M. Martin, and G.A. Lamberti. 2002. Interactions among zebra mussel shells, invertebrate prey, and Eurasian ruffe or yellow perch. Journal of Great Lakes Research 28(4):664-673.

Leigh, P. 1998. Benefits and costs of the ruffe control program for the Great Lakes fishery. Journal of Great Lakes Research 24(2):351-360.

Leino, R.L., and J.H. McCormick. 1997. Reproductive characteristics of the ruffe, Gymnocephalus cernuus, in the St. Louis River estuary on western Lake Superior: a histological examination of the ovaries over one annual cycle. Canadian Journal of Fisheries and Aquatic Sciences 54:256-263.

Maitland, P.S. 1977. The Hamlyn guide to freshwater fishes of Britain and Europe. Hamlyn Publishing Group Limited, New York, NY.

Marking, L.L. and T.D. Bills. 1985. Effects of contaminants on toxicity of the lampricides TFM and Bayer 73 to three species of fish. Journal of Great Lakes Research 11(2):171-178.

Mayo, K.R., J.H. Selgeby, and M.E. McDonald. 1998. A bioengetics modeling evaluation of top-down control of ruffe in the St. Louis River, western Lake Superior. Journal of Great Lakes Research 24 (2): 329-342.

McLean, M. 1993. Ruffe (Gymnocephalus cernuus) fact sheet. Minnesota Sea Grant Program, Great Lakes Sea Grant Network, Duluth, MN.

Ogle, D.H., B.A. Ray, and W.P. Brown. 2004. Diet of larval ruffe (Gymnocephalus cernuus) in the St. Louis River harbor, Lake Superior. Journal of Great Lakes Research 30(2):287-292.

Ogle, D.H., J.H. Selgeby, J.F. Savino, R.M. Newman, and M.G. Henry. 1995. Diet and feeding periodicity of ruffe in the St. Louis River estuary, Lake Superior. Transactions of the American Fisheries Society 124:356-369.

Ogle, D.H., J.H. Selgeby, J.F. Savino, R.M. Newman, and M.G. Henry. 1996. Predation on ruffe by native fishes of the St. Louis River estuary, Lake Superior, 1989-1991. North American Journal of Fisheries Management 16:115-123.

Page, L.M., and B.M. Burr. 1991. A Field Guide to Freshwater Fishes of North America north of Mexico. The Peterson Guide Series 42: 432 pp.

Pearce, J. – Michigan Department of Natural Resources, Baraga Operations Service Center, Baraga, Michigan.

Pratt, D. 1988. Distribution and population status of the ruffe (Gymnocephalus cernua) in the St. Louis estuary and Lake Superior. Great Lakes Fishery Commission, Research Completion Report. 12 pp.

Pratt, D.M., W.H. Blust, and J.H. Selgeby. 1992. Ruffe, Gymnocephalus cernuus: newly introduced in North America. Canadian Journal of Fisheries and Aquatic Sciences 49:1616-16.

Raloff, J. 1992. From tough ruffe to quagga; intimidating invaders alter earth's largest freshwater ecosystem. July 25, 1992. Science News 142(4):56-58.

Ruffe Task Force. 1992. Ruffe in the Great Lakes: a threat to North American fisheries. Great Lakes Fishery Commission, Ann Arbor, MI.

Sandlund, O.T., T.F. Naesje, L. Klyke, and T. Lindem. 1985. The vertical distribution of fish species in Lake Jmosa, Norway as shown by gillnet catches and echo sounder. Institute of Freshwater Research, Drottningholm 63: 136-149.

Savino, J.F., and C.S. Kolar. 1996. Competition between nonindigenous ruffe and native yellow perch in laboratory studies. Transactions of the American Fisheries Society 125(4):562-571.

Scheidegger, K. – Wisconsin Department of Natural Resources, Madison, Wisconsin.

Selgeby, J. 1998. Predation by ruffe (Gymnocephalus cernuus) on fish eggs in Lake Superior. Journal of Great Lakes Research 24(2):304-308.

Simon, T.P., and J.T. Vondruska. 1991. Larval identification of the ruffe, Gymnocephalus cernuus (Linnaeus) (Percidae: Percini), in the St. Louis River Estuary, Lake Superior drainage basin, Minnesota. Canadian Journal of Zoology 69: 436-441.

Slade, J. – U.S. Fish and Wildlife Service, Ludington Biological Station, Ludington, Michigan.

Starnes, W. - North Carolina State Museum of Natural Sciences, Raleigh, North Carolina.

Stepien, C.A., A.K. Dillon, and M.D. Chandler. 1998. Genetic identity, phylogeography, and systematics of ruffe Gymnocephalus in the North American Great Lakes and Eurasia. Journal of Great Lakes Research 24 (2): 361-378.

Tilmant, J.T. 1999. Management of nonindigenous aquatic fish in the U.S. National Park System. National Park Service. 50 pp.

Underhill, J.C. 1989. The distribution of Minnesota fishes and late Pleistocene glaciation. Journal of the Minnesota Academy of Science 55(1):32-37.

U.S. Environmental Protection Agency (USEPA). 2008. Predicting future introductions of nonindigenous species to the Great Lakes. National Center for Environmental Assessment, Washington, DC; EPA/600/R-08/066F. Available from the National Technical Information Service, Springfield, VA, and

Wheeler, A. 1969. The fishes of the British Isles and north-west Europe. Michigan State University Press, East Lansing, MI. 613 pp.

Wheeler, A. 1978. Key to the fishes of northern Europe. Frederick Warne Ltd., London, England.

Zorn, T. – Michigan Department of Natural Resources, Marquette, Michigan.

FishBase Fact Sheet

Author: Fuller, P. G. Jacobs, J. Larson, T.H. Makled and A. Fusaro

Revision Date: 5/13/2014

Citation Information:
Fuller, P. G. Jacobs, J. Larson, T.H. Makled and A. Fusaro. 2016. Gymnocephalus cernua. USGS Nonindigenous Aquatic Species Database, Gainesville, FL. Revision Date: 5/13/2014

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Citation information: U.S. Geological Survey. [2016]. Nonindigenous Aquatic Species Database. Gainesville, Florida. Accessed [7/30/2016].

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