""""RUF F E

reproductive capacity, and adapts to a wide variety of environments,it is considereda serious threat to commercial and sport fishing. It also has the potential to seriously disrupt the delicate predator/prey balance vital to sustaining a healthy fishery. Effects of the ruffe on found in the WesternHemisphere. Ruffe's ability to move from lake to other species lake in ships' ballast, however, will Explosivegrowth of the ruffe make it difficult to prevent the populationmeans less food and space from expanding its range to the lower in the ecosystemfor otherfish with , similar diets and feeding habits. Becauseof this, , , and a Control strategiesin the number of smallforage fish speciesare St. Louis River. seriously threatenedby continued Fisheriesmanagers first tried to expansionof the ruffe's range. control ruffe by increasingthe number While it is too early to tell exactly how of its predators,especially walleye and the ruffe will affect other fish in the St. northernpike. Theydid this by Louis River,Duluth/Superior harbor limiting sport catchesof thesespecies, area of , its numbers and stockingwalleye and northern have increaseddramaticagy while pike. Earlyresults of thepredator otherspecies, especially emerald stocking program have been shiner, and troutperch, disappointing, but it is too early to have declined SeeGraph 1!, It would judgethe effectivenessof this be easy to blame all of thesechanges approachsince fish oftentake several on the ruffe, but some could be the yearsto switch to a newfood source. result of natural fluctuations, fishing Researchersanalyzed stomach pressure,or fisheries management samplesof the predators and found practices, veryfew ruffe in walleyestomachs. Bullheadsappear to be the only How fast is the ruffe speciesthat consistentlyeat ruffe. spreading? Researchsuggests that predators The ruffe was first collected in the stockedto control ruffe may not eat Duluth/Superior harborarea of Lake them becausethey prefer soft-rayed Superior in ] 986during a routine shinersand small hard-rayed fish like analysis of the local fishery, The first darters and young perch. This could official identification of ruffe was in explainthe increasein ruffe and 1987,but it was probably introduced reductionin theseforage species. about 1985. In the short time since its Recentsurveys of northern pike introduction, the ruffe has become the stomachs,however, suggestthat ruffe most numerous fish in the St, Louis may be growing in importance as a River, as measuredby trawl samples, food source. Ruffe made up less than As of 1993, the ruffe has spread east one percentof fish eatenby northern along LakeSuperior's coastto pike in 1989,By 1992, the figurehad ChequamegonBay in northern climbed to 15 percent. Wisconsin,and northto ThunderBay, Ontario,Ruffe probablymoved across The battleto keep the ruffe from the lake to ThunderBay via intralake spreadingis beingfought on several ballast exchange. So far, Lake fronts. For instance,poison may be Superioris the onlyplace the ruffeis used to eradicate ruffe when the fish is What does a mffe look like?

The ruffe is a small fish that resemblesa yellow perch with walleye markings. In fact, it is a memberof the perchfamily. An adult ruffe is about five to six inches long, It rarelyexceeds 10 inches in length. At firstglance, ruffe can resemble youngwalleye, yellow perch, johnny darter, or troutperch, but there are waysto tell the difference, The most obvious differences are the ruffe'slarge, continuous and its slightlydownturned mouth. Other distinguishing characteristics; ~ size: ruffe are small, adults average4-6 inches in length ~ color.color and markingsare similar to walleye. Theaverage ruffe is 4+ incheslong

The ruffe is a member of the perchfamily, so... TROUTPERCH ~ it hasspiny dorsaland anal fins part of this largedorsal fin has11-16 ~ it hastwo finson top, thefront fin spines. has hardand sharp spines also ~ it hasa slightlydownturned calledrays!, the backfin hassoft rays. mouth

and ~ it has no scales on its head The ruffe is different from other Don't mistakeruffe for troutperch. perchbecause... Troutperchare a softrayedfish with a ~ it hasa verylarge dorsal fin, joined singletop fin,and are smaller than together,front andback The front ruffe.

found in small numbers at a new destroyas many ruffe as possible in location. Poisoningwas considered theSt. LouisRiver, on the theorythat for areas where the ruffe is firmly theruffe's range would not expand as entrenched, but was ruled out. As one rapidlyif populationswere controlled. researchersaid, "The cost would have Fisheriesmanagers will plan beenstaggering, and it probably eradication and control measuresfor would have failed. All it takes is one LakeSuperior rivers and streamson a pairof ruffeto survive and the caseby casebasis. The overall goal, problemstarts all overagain." however,is to containruffe to the Chemical controls that kill ruffe but westernpart of LakeSuperior. To leaveother species unharmed are keepruffe from spreading tothe other beingsought. For instance,researchers Great Lakes, the Lake Carriers areexploring the possibility that the Associationdeveloped voluntary ruffe is susceptibleto low dosesof the guidelinesfor handlingballast water lampricideTFM, a chemicalthat in low in GreatLakes ships. Under thesenew doseskills lamprey but not otherfish. guidelines,ships going to other Great Recent field tests have shown that Lakesare required to exchange ballast treatingstreams with TFM for lamprey in deep at least240 feet! water west of controlkills a highpercentage of the a demarcation line between Onton- ruffe. TFM, however, is only agon,Michigan and Grand Portage, registeredfor useon lamprey. Minnesota and at least five miles from Fisheriesmanagers have also the south shore of Lake Superior considereda programto net and What do we know In rivers, the ruffe prefers slower- moving water; in lakes,it prefers about ruffe? turbid areas and soft bottoms, usually Because ruffe are so new to North without vegeta tion. America, fisheriesmanagers rely on Europeanstudies that describetheir Unlike other perch species,the ruffe is life cycle and habits. Even with these more tolerant of murky, nutrient-rich data, it is difficult to predict how an eutrophic!, conditions See Graph 3!, exotic specieswill act in a new Like walleye, the ruffe spendsits days environment. in deeper water and moves to the shallows to feed at night, In Europe, the ruffe generally matures in two or three years, but it may To avoid predators, the ruffe prefers mature in one year in warmer waters. darkness.Although it has poor It spawnsbetween mid-April and July, eyesight,the ru ffe'shead has a well depending on location, water developed system of bone canalsthat temperature,and preferredhabitat. A contain sensoryorgans called Fernaleruffe lives an averageof seven "neuromasts." Such organs are years,but may live up to 11 years. common among perch speciesin early Maleslive up to sevenyears but have life stages,but they tend to atrophy as an averagelifespan of three to five the fish reach adulthood. In adult ruffe, however, thesesensory organs years. continue to detect water vibrations The ruffe's range includes given off by both predators and prey. northeasternFrance, England, the rivers entering the Baltic and White Do ruHe eat other Seas,most of Siberia, and the Baltic Sea, Beforecoming to , fish's eggs? the ruffe's most recent expansion was ln Europe, the ruffe is known to eat to Loch Lomond, Scotland where it other fish's eggs,but its main diet mayhave been responsible for consists of small water insects and dramaticdeclines in the local perch larvaefound primarily in the bottom population SeeGraph 2!. benthic! layer of the water column. In the St. Louis River, an important A hearty species hatcheryarea for many Lake Superior fish,ruffe stomachsamples reveal few The ruffe can thrivein a wide rangeof fish eggs.But the ruffe is an temperaturesand . The ruffe opportunisticfeeder and will eat hasa fasterfirst yeargrowth rate than almost anything. So far, the ruffe most of its competitors. It starts seems to have the same basic diet of reproducingat agetwo or three,but insects and larvae it has in its native canreproduce after the first year in Eurasian environment. While fish warmerwaters. An averagefemale eggsdo not seemto be part of the canproduce 13,000 to 200,000eggs per ruffe's regular diet in the St. Louis season.Due in part to its hearty River,that's no guaranteefish eggs reproductive rate, ruffe populations won't be part of the ruffe's diet in canexplode quickly. other North American . in Europe,the ruffe is found in fresh and brackish salinity less than3-5 The "bottleneck eff ect" pprn!waters and in all typesof Whether ruffe feed on fish eggs may lakes from deep,cold, and clearto be lessimportant than whether ruffe shallow, warm and full of nutrients. eat the foodpreFerred by otherfish. Because of its sheer numbers, and the varietyof foodit eats,the ruffe will reducefood sources for many fish species.If the ruffe,in turn, is not eatenby nativepredators or if young predator fish starve before they get big enoughto eat ruffe,the result will be an explosionof ruffe and population bottlenecks in other species. Forexample, recently hatched yellow perchmust consumelarge amountsof plankton in a fairly short time in order to grow to the nextstage. At stage leaving the landing. Even canoes two, yellow perch must eat larger food should be checked inside and out, items small crustaceans and insects Drain live wells, bait buckets, and abundant near the bottom of the bilge areas.Inspect and clean fishing watercolumn. Only afterpassing tackle, Let your boat and trailer dry in these two hurdles do yellow perch get the sun for at least three days before big enoughto eatother fish, If the your useit againin anotherlake or ruffe interrupts either growth stageby river. Or, wash your boat with very reducingthe foodsupply just asthe hot water at least I05 degreesF!, yellow perchneed it an ecological bottleneck!, the yellow perch population will crash. Ruffe are a threat to fisheries What you can do to slow Predicting the effect of any exotic the spread of ruffe specieson its newhome is difficult. The ruffe is no exception.Experience Becauseruffe couldeasily spread to in Scotland and Russia, however, inland waters, the Minnesota and pointsto seriousproblems for North Wisconsin departmentsof natural American fisheriesif ruffe escapes resourcesenforce regulations that from its limited range in westernLake makeit illegalto transportruffe, dead Superior.In LochLomond, Scotland, or alive. native perch populations declined The ruffe cannot be used as bait by dramatically when the ruffe was anglers,and bait dealerswho trap in introduced. In some Russian waters, areas infested with ruffe should take the ruffe has harmed whitefish specialprecautions to insure they are populationsby preyingheavily on not contributing to the spread of this whitefisheggs. Movement of the ruffe exotic species. to the lower Great Lakes, or to inland lakes and rivers could have The ruffe is one of a number of exotic devastating consequences. speciescausing concern in theGreat Lakes region. You can help prevent the spreadof exoticspecies with a thoroughinspection of your boatand fishinggear. Clean all mud andplant matter from your boat, trailer, propeller,live well and anchors before For moj;e information Illinois-Indiana Sea Grant 65 Mumford HaIl New York Sea Grant 1301W. Gregory Dr Dutchess Hall Rm 137 Urbana, IL 61801 SUNY at Stony Brook Phone: 217/333-9448 Stony Brook, NY 11794 Phone; 516/632-6905 Sea Grant University of Wisconsin Ohio Sea Grant 1800University Avenue Ohio State University Madison, WI 53705 1314 Kinnear Rd Phone: 608/263-3259 Columbus, OH 43212 Phone: 614/292-8949 MichiganSea Grant University of Michigan US Fish and Wildlife Service 2200 Bonis teel Blvd. 2800 Lakeshore Drive East, Suite B Ann Arbor, Ml 48109-2099 Ashland, WI 54806 Phone: 313/764-1138 Phone: 715/682-6185

Minnesota Sea Grant MN Dept.of Natural Resources University of Minnesota ExoticSpecies Program Ofhce 1518 Cleveland Ave N 500 Lafayette Rd. Rm 302 St. Paul, MN 55155 St. Paul, MN 55108 Phone: 6 I 2/297-1464 Phone: 612/625-6781

Credits: The Great Lakes Sea Grant Network is a cooperativeprogram of theIllinois-indiana, Written by Mike McLean, MinnesotaSea Michigan,Minnesota, New York,Ohio, and Grant communicator, with technical assistancefrom DerekOgle, University of Wisconsin Sea Grant programs. Sea Grant is a university-basedprogram designedto Minnesota Department of Fisheries,and supportgreater knowledge and wise use of JeffreyGunderson, Minnesota Sea Grant the Great Lakes and ocean resources. assistantfisheries specialist. Edited by Through its network of advisory agents, Alice Tibbetts, Minnesota Sea Grant researchers, educators, and communicators, communications coordinator. the Great Lakes Sea Grant Network Troutperch illustration: copyright 1975,Dr. suppliesthe regionwith usablesolutions to W. B. Scott,used with permission. pressingproblems and provides the basic information needed to better manage the Yellowperch illustration: copyright 1957, Great Lakesfor both presentand future SamuelEddy, Wrn. C, Brown Publishers, generations.Sea Grant is in thc National used with permission. Oceanicand Atmospheric Administration Ruffe illustration: Copeia1974. No, 2 NOAA!, Department of Commerce. Graphscreated from informationfound in TrophicRelations of Ruffe Gyrnnocepkalus cernuus! in the St, Louis River Harbor, Lake Superiorby Derek Ogle, June 1992.

Producedby the Minnesota SeaGrant Programas a jointProject of the Great Lakes Sea Grant Network, Spring 1993, Minnesota Sea Grant is a statewide program that supports research, O extension, and educahonal programs related to Lake Superior and Minnesota's water resources. Sea Grant offices are located on the Twin Cities and Duluthcampuses of the Universityof Minnesota. Sea Grant is funded by the National Oceanicand Atmospheric Administration through the US Department of Commerce;the statelegislature; and the University of Minnesota.