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<br />kills fish by attaching to its prey and feeding on body fluids, devastated populations of whitefish <br />and lake trout. The predation of the sea lamprey on this valuable commercial fishery permitted <br />populations of commercially less valuable fish to proliferate. In 1992, annual sea lamprey <br />control costs and research to reduce its predation were approximated at $10 million annually. <br />The total value of the lost fishing opportunities plus indirect economic impacts could exceed <br />$500 million annually (Office of Technology Assessment, 1993). <br />The nonindigenous populations of alewife increased rapidly in the Great Lakes during the 1940s <br />and 1950's because of the suitability of the habitat and the fact that predators were not <br />sufficiently abundant to check their growth. Consequently, periodic die-offs fouled recreational <br />beaches and blocked municipal and industrial water intakes. While the alewife out-competed <br />and suppressed whitefish, yellow perch, emerald shiners and rainbow smelt, it subsequently <br />became a fish preyed upon by introduced trout and salmon. The alewife has permanently altered <br />the existing predator-prey relationships in the Great Lakes ecosystem. <br />The ruffe, a Eurasian fish of the perch family, was introduced to North America in the 1980s, <br />most likely through the ballast water of a seagoing vessel. This aquatic nuisance species has few <br />predators, no commercial or recreational value and is replacing valuable native fishes. Since its <br />introduction, the ruffe has become established in the nearshore waters of western Lake Superior, <br />with an estimated average rate of range expansion of 18 shoreline miles per year. By the fall of <br />1994, ruffe populations were found in Michigan waters of Lake Superior and in August of 1995, <br />three ruffe were discovered in a commercial harbor in northern Lake Huron, more than 300 miles <br />east of the previously known range. The ruffe has become the most abundant species in Duluth <br />Harbor. Based on observations of present ruffe migration rates along with native fish population <br />displacements in Lake Superior, as well as past experience of ruffe in European waters, it appears <br />that ruffe will be in direct competition with yellow perch and whitefish populations. Walleye <br />populations are affected indirectly through a change in the food chain composition brought on by <br />the proliferation of the ruffe. Based on moderate estimates of expected declines of yellow perch, <br />whitefish and walleye, the annual economic loss to the U.S. sport and commercial fisheries is <br />estimated at approximately $119 million if the ruffe suddenly proliferates to all lake regions <br />(Leigh, 1994). <br />The round goby and the tubenose goby were introduced via ballast water into the St. Clair River, <br />near Detroit in 1990. The tubenose goby has not thrived, but the round goby has spread into <br />Lake Erie and Lake Michigan where the largest population is found. The round goby was <br />observed in the St. Louis River Estuary in Lake Superior during the summer of 1995. The <br />primary concern with the round goby is the tremendous range expansion exhibited since its <br />introduction in 1990. It is a very aggressive fish, and feeds voraciously upon bottom-feeding <br />fishes (e.g., sculpin, darters and logperch), snails, mussels and aquatic insects. The Great Lakes <br />fisheries, particularly those in Lake Michigan and Lake Erie, are threatened by this aquatic <br />nuisance species due to its robust characteristics and ability to displace native species from prime <br />habitat and spawning areas. <br />DRAFT ANS Plan for CRFWC (April 23-24,1998) Page 4 <br /> <br />1 <br />11 <br /> <br /> <br /> <br /> <br />1 <br /> <br /> <br /> <br /> <br /> <br /> <br />1 <br /> <br />0 <br />L1