Scientific Name: Gymnocephalus cernua

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Identification: This small fish is also known as the Eurasian ruffe, blacktail, pope, redfin darter, and river ruffe. Its back is olive-brown to golden-brown, and its underside is yellowish-white. Its dorsal fins are fused and generally have 12 to 19 spines.

Size: Ruffe grows to 4-6 inches (10-15 cm) in length.

Native Range: This species is native to northern Europe and Asia.

Table 1. Great Lakes region nonindigenous occurrences, the earliest and latest observations in each state/province, and the tally and names of HUCs with observations†. Names and dates are hyperlinked to their relevant specimen records. The list of references for all nonindigenous occurrences of Gymnocephalus cernua are found here.

Full list of USGS occurrences

State/ProvinceYear of earliest observationYear of last observationTotal HUCs with observations†HUCs with observations†
Michigan1994201913Betsy-Chocolay; Black-Presque Isle; Cheboygan; Keweenaw Peninsula; Lake Huron; Lake Michigan; Lake Superior; Lone Lake-Ocqueoc; Ontonagon; St. Marys; Sturgeon; Thunder Bay; Waiska
Minnesota198620163Beaver-Lester; Lake Superior; St. Louis
Wisconsin198620165Bad-Montreal; Beartrap-Nemadji; Lake Michigan; Lake Superior; St. Louis

Table last updated 9/30/2019

† Populations may not be currently present.

* HUCs are not listed for areas where the observation(s) cannot be approximated to a HUC (e.g. state centroids or Canadian provinces).

Means of Introduction: Ruffe was probably introduced by water discharged from a vessel arriving from a Eurasian port, possibly as early as 1982-1983. Shipping transport among the Great Lakes may have increased the species’ spread.

Status: Ruffe was first collected in 1986 from the St. Louis River at the border of Minnesota and Wisconsin. It then spread to Lake Superior, Lake Michigan, and several surrounding lakes and rivers. It is believed the species could find suitable habitat almost anywhere in the Great Lakes. It is considered the most abundant of the 60 fish species found in Duluth Harbor and is estimated to make up 80 percent of fish living in the southwestern region of Lake Superior.

Remarks: Research has shown that certain native species feed on introduced ruffe. However, the same study indicated that predation is unlikely to effectively prevent ruffe from colonizing new areas in the Great Lakes.

Author: Illinois-Indiana Sea Grant

Contributing Agencies:
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Revision Date: 4/24/2012

Citation for this information:
Illinois-Indiana Sea Grant, 2019, Ruffe: U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, and NOAA Great Lakes Aquatic Nonindigenous Species Information System, Ann Arbor, MI,, Revision Date: 4/24/2012, Access Date: 10/13/2019

This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.