Ruffe  (Gymnocephalus cernuus)

DESCRIPTION

The Ruffe (Gymnocephalus cernuus), a small spiny fish native to fresh and brackish waters in portions of Eurasia.

A relative of the perch, the ruffe spends its days in deeper water and moves to the shallows to feed at night. Ruffe in the Great Lakes seem to be most common in or near river mouths. To avoid predators, the ruffe prefers darkness, and uses special sensory organs called "neuromasts" to detect predators and prey. The ruffe also has a large, spiny dorsal fin likely unpalatable to predators.

• Length: 4 to 6 inches(25 cm)
• Coloring: olive-brown to golden-brown on back, paler on the sides with yellowish white undersides
• Common Names: Eurasian ruffe, river ruffe, pope
• Found in Lakes: Huron and Superior

(Source: Great Lakes Information Network, http://www.great-lakes.net/envt/exotic/ruffe.html; Wisconsin sea grant, http://www.seagrant.wisc.edu/greatlakesfish/framefish.html)

IMPACTS

Ruffe's high reproductive rate & feeding efficiency

Explosive growth of the ruffe population means less food and space in the ecosystem for other fish with similar diets and feeding habits. The ruffe competes with native fish for food and habitat. Because of this, walleye, perch, and a number of small forage fish species are seriously threatened by continued expansion of the ruffe's range.

While it is too early to tell exactly how the ruffe will affect other fish in the St. Louis River and Duluth/Superior harbor area of Lake Superior, its numbers have increased dramatically while other species, especially emerald shiner, yellow perch and troutperch, have declined. It would be easy to blame all of these changes on the ruffe, but some could be the result of natural fluctuations, fishing pressure, or fisheries management practices. In addition, it is considered a serious threat to commercial and sport fishing because the ruffe grows very fast, and adapts to a wide variety of environments. 

(Source:  Wisconsin sea grant, http://www.seagrant.wisc.edu/greatlakesfish/framefish.html; Great Lakes Information Network, http://www.great-lakes.net/envt/flora-fauna/invasive/ruffe.html)

(Source:  Wisconsin sea grant, http://www.seagrant.wisc.edu/greatlakesfish/framefish.html)

WHAT YOU CAN DO

• If you catch a ruffe, kill it, freeze it, and call a local DNR fishery office, or Local Sea Grant Office or Extension. 
  Do not throw it back alive!
• Always drain your livewells, bilge water, and transom wells before leaving the water access.
• Never empty your bait bucket into the water, always empty it on land.
• Never dip your bait bucket into one lake if it has water in it from another.
• Never dump live fish from one body of water into another.

(Source from Minnesota Sea Grant, http://www.seagrant.umn.edu/exotics/ruffeid.html)

CONTROL STRATEGIES in the St. Louis River

Fisheries managers first tried to control ruffe by increasing their number of predators, especially walleye and northern pike. They did this by limiting sport catches of these species, and stocking walleye and northern pike. Early results of the predator stocking program have been disappointing, but it is too early to judge the effectiveness of this approach since fish often take several years to switch to a new food source.

Researchers analyzed stomach samples of the predators and found very few ruffe in walleye and northern pike stomachs. Bullheads appear to be the only species that consistently eat ruffe. Research suggests that predators stocked to control ruffe may not eat them because they prefer soft-rayed shiners and small hard-rayed fish like darters and young perch. This could explain the increase in ruffe and reduction in these forage species.

The battle to keep the ruffe from spreading is being fought on several fronts. For instance, poison will be used to eradicate ruffe when the fish is found in small numbers at a new location. Poisoning was considered for areas where the ruffe is firmly entrenched, but was ruled out. As one researcher said, "The cost would have been staggering, and it probably would have failed. All it takes is one pair of ruffe to survive and the problem starts all over again."

Chemical controls that kill ruffe but leave other species unharmed are being sought. For instance, researchers are exploring the possibility that the ruffe is susceptible to low doses of the lampricide TFM, a chemical that in low doses kills lamprey but not other fish. Recent field tests have shown that treating streams with TFM for lamprey control kills a high percentage of the ruffe. TFM, however, is registered for use on lamprey only. Fisheries managers have also considered a program to net and destroy as many ruffe as possible in the St. Louis River, on the theory that the ruffe's range would not expand as rapidly if populations were controlled.

Fisheries managers will plan eradication and control measures for Lake Superior rivers and streams on a case-by-case basis. The overall goal, however, is to contain ruffe to the western part of Lake Superior. To keep ruffe from spreading to the other Great Lakes, the Lake Carriers Association developed voluntary guidelines for handling ballast water in Great Lakes ships. Under these new guidelines, ships going to other Great Lakes are required to exchange ballast in deep (at least 240 feet) water west of a demarcation line between Ontonagon, Michigan and Grand Portage, Minnesota and at least five miles from the south shore of Lake Superior.

(Source from Ohio Sea Grant Fact Sheet 064, http://www.sg.ohio-state.edu/PDFS/PUBLICATIONS/FS/FS-064.PDF)

Aquatic Nuisance Species: Algae, Bythotrephes, Gobies: Ohio Sea Grant
    http://www.sg.ohio-state.edu/SEARCH/TOPICS/T-ANS.HTM
Publications from Ohio Sea Grant explore various exotic species. 
FS-064  Ruffe: A serious threat to North American fisheries.
     - Effects of the ruffe on other species
     - How fast is the ruffe spreading?
     - What do we really know about ruffe?
     - What you can do
     - Do ruffe eat other fish's eggs?
     - The "bottleneck effect"
     - A hearty species

Ruffe Home Page: University of Minnesota  http://www.fw.umn.edu/research/ruffe/
This page provides web-based information on Eurasian ruffe Gymnocephalus cernuus. 
Ruffe scientific resources  http://www.fw.umn.edu/research/ruffe/rsrcs/rsrcs.HTM
Ruffe Researchers  http://www.fw.umn.edu/research/ruffe/people/people.HTM

Ruffe Distribution Map (July 1999): the United States Geological Survey (USGS)
    http://nas.er.usgs.gov/fishes/images/ruffe_map.gif
This map shows the current geographic distribution of Ruffe in North America.

Ruffe: A New Threat to Fisheries  http://www.engin.umich.edu/seagrant/pubs/on/msg96-501.html

Ruffe: a New Threat to Our Fisheries
    http://www.seagrant.umn.edu/exotics/ruffe.html
This is a basic fact sheet about the origins, biology, and disruptive potential of Gymnocephalus cernuus with illustrations.

Sea Grant Seiche--Can Native Fish Help Control Ruffe? 
    http://www.seagrant.umn.edu/seiche/sep.96/art05.html

Sea Grant Seiche--"Bone-Cold Café" Suits Ruffe (by Sharon Moen)  
    http://www.seagrant.umn.edu/seiche/jun.00/art03.html

Sea Grant Seiche--the smell of fear  (by Sharon Moen)  
    http://www.seagrant.umn.edu/seiche/jan.01/art03.html

Sea Grant Seiche--Great Lakes Impacts "Ruffed" Out at International Symposium  
   http://www.seagrant.umn.edu/seiche/may.97/art01.html

Sea Grant Seiche--Outdoor Writers Learn about Fisheries Conflicts and Ruffe
    http://www.seagrant.umn.edu/seiche/sep.96/art06.html

Ruffe Waters Ahead for All the Great Lakes?
    http://www.d.umn.edu/seagr/seiche/march.95/r_waters.html
An update article on ruffe distribution by Marie Sales from Minnesota Sea Grant

Eurasian Ruffe; Great Lakes Brace for a Ruffe Time
    http://www-personal.umich.edu/~srraymon/ruffle.htm
A basic informational article about ruffe by Terry Picard. Originally appeared in the February 1995 issue of Walleye World.

Fishery Management Officials Re-Examine Ruffe Control Strategy After the Recent Appearance of Ruffe in Lake Huron: Council of Lake Committees, Great Lakes Fishery Commission
    http://www.glfc.org/pressrel/clcrufpr.htm
Officials agree that ruffe movement warrants a new approach to deal with this exotic menace. November 15, 1995.

Ruffe: the U.S. Geological Survey, Florida Caribbean Science Center List
    http://nas.er.usgs.gov/fishes/accounts/percidae/gy_cernu.html
Basic information on Gymnocephalus cernuus: taxonomy, physical description, native distribution, current distribution, discussion of possible impacts. 

Article by the Great Lakes Sportfishing 
Council reports on new research demonstrating that the enhancement of native piscivore populations shows little promise as a means of ruffe control.

Grant Lakes Information Network (GLIN): Invasive Species in the Great Lakes Region     
     http://www.great-lakes.net/envt/flora-fauna/invasive/invasive.html
This site includes a comprehensive information on invasive species in the Great Lakes. 
Ruffe    http://www.great-lakes.net/envt/flora-fauna/invasive/ruffe.html