Photographer: Tiit Hunt Source: Wikimedia Commons Copyright: CC BY-SA 3.0 US
Gymnocephalus cernua is a member of the Perch family. It is an olive-brown to golden-brown fish with yellowish white undersides. It is a smaller fish, getting no larger than 10 inches. Dorsal fins have 12-19 spines followed by 11-16 soft rays.
The Eurasian ruffe is able to reproduce quickly, and establish large populations. In some portions of Lake Superior, they were estimated to make up 80% of the fish abundances. As they grow in size, their diet becomes more benthic. Micro and Macroinvertebrates such as copepods, and insect larvae and important to the ruffe’s diet. Their wide prey selection competes with the diet of native species like the yellow perch (Perca flavescens).
The ruffe produces by sexual reproduction and lays eggs thereafter. Their eggs have a sticky surface that allows them to adhere to plants and rocks. One female can lay from 130,000-200,000 eggs in one year. After 5-12 days the eggs hatch, spawning occurs from April through June. One week after hatching, they start to swim and feed. Gymnocephalus cernua are sexually mature at 2-3 years and can live from 7-11 years.
First collected from the St. Louis River between Minnesota and Wisconsin in 1987. Thought to be accidentally introduced through ship ballast water from a vessel coming from Eurasia.
Northern Europe and Asia
U.S. Habitat: Freshwater Rivers and lakes. However, it does seem to be intolerant of deeper waters.
U.S. Present: MI, MN and WI
For a point collection map provided by the U.S. Geological Survey click here.
The coloration of the ruffe can look similar to the walleye (Sander vitreus).
The key to managing the Eurasian ruffe is prevention by educating the public, and limiting the commercial/personal sale and transportation of live fish. In surrounding states such as, Illinois, Indiana, and Pennsylvania, it is unlawful to import or introduce live ruffe into the states, and local waters. Ohio allows live ruffe importation for research, education, or for an authorized public display. The states currently affected have this fish listed as a restricted or prohibited species.
Researchers have tried top-down control programs, by introducing native predator fish such as walleye, northern pike and brown bullhead. However, despite reducing ruffe biomass in the environment, the predators avoided the ruffe and preferred feeding on native prey fish; making their impact negative. There are four chemical piscicides allowed for use in the Unites States: antimycin A, rotenone, TFM, and bayluscide. Unfortunately, there can be non-target kills associated with this form of management.
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.
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.
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.
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
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.