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Kraft, C., JUNE, 1994. Zebra Mussel Update #21, University of Wisconsin-Madison, Wisconsin Sea Grant Institute A Newsletter produced by the Wisconsin Sea Grant Institute Zebra Mussel Update #21New Sighting ANN ARBOR, Mich. -- Two zebra mussels were found in late April at Portage Lake by Renee Sherman, a graduate student at the University of Michigan. Sherman found the large mussels -- 20 and 16 mm in length -- attached to rocks while she was surveying the lake bottom for native Unionid mollusks. No veligers were found in a June 1993 plankton sample collected from Portage Lake by Paul Marangelo, a Michigan Sea Grant-supported biologist who helped conduct the 1993 Michigan inland lake monitoring program. (Marangelo also searched for settled zebra mussels attached to macrophytes in Portage Lake, but didn't find any.) Marangelo said he expects more zebra mussels will be found in this lake, which has a public boat landing that receives "moderately heavy" recreational use. Further plankton samples and mussel surveys will be conducted this summer. ID: 199406-1. Inland Lake Sighting Given the high volume of boat traffic between infested and uninfested inland waters, the overland spread of zebra mussels may have proceeded more slowly than has been generally acknowledged. University of California-Santa Barbara's Ladd Johnson and the author of this publication have prepared a list of eight zebra mussel-infested inland lakes which required overland transport for colonization. We have only included lakes reported to contain populations of adult mussels. They are: Eagle, Loon and Portage lakes in Michigan; Lake Wawasee in Indiana; White Star Quarry and Hargus Lake in Ohio; and Conesus Lake and Hinkley Reservoir in New York. This list excludes New York's "Finger Lakes," the drowned river mouths of western Michigan, and lakes on the Trent-Severn Canal or Rideau Canal systems in Canada, all of which have navigable connections with infested waters of the Great Lakes and nearby waterways. We invite additions or corrections to our list. Johnson can be reached at (805) 893-7295; Kraft at (414) 465-2795, or via email at KRAFTC@UWGB.EDU. ID: 199406-2. Ontario Sightings The aforementioned North American inland lake sightings exclude two Ontario sightings which appear on zebra mussel maps distributed by the Ontario Ministry of Natural Resources. Both sightings took place in 1991. A single veliger was detected in Lake Muskoka, and one veliger and one floating adult "translocator" were found in a water sample from nearby Lake Rosseau. The mussels were identified by personnel at the University of Guelph, according to Ontario Ministry of Natural Resources' Warren Dunlop. No subsequent mussel sightings occurred during a similar monitoring program conducted in 1992, Dunlop said. The monitoring program was terminated following that season, though navigation buoys retrieved by the Canadian Coast Guard have been periodically inspected. No settled mussels have been found. Because both Lake Muskoka and Lake Rosseau are populated by home owners, Dunlop said he would likely get calls if mussels turn up on a boat dock or hull. Calcium levels in these lakes are probably too low --around 5 mg per liter -- to sustain a substantial mussel population, he said. ID: 199406-3. Fish Tags Covered with Mussels GREEN BAY, Wis. -- Zebra mussels were found attached to thin plastic tags implanted in three northern pike caught this spring in southern Green Bay. Two of the tags were returned to Wisconsin Department of Natural Resources (WDNR) personnel without the attached mussels, but the third tag was returned with at least 40 intact mussels. The mussel-encrusted tag was retrieved from a 33-inch northern pike caught just south of Longtail Point. The fish was tagged two years ago near DePere Dam in the Fox River. The tag became detached as the fish was brought up through a hole in the ice, according to Dan DuBois, who caught the fish. WDNR fish manager Terry Lychwick said zebra mussels on fish tags could produce problems estimating northern pike exploitation rates. Other than fish mortality, any factor that causes tags to fall off jeopardizes the WDNR's ability to estimate vital population parameters. Another concern is whether fish are impaired by mussel-covered tags. Northern pike are slow-moving "lie-and-wait" predators, which might increase their contact with settling zebra mussels. While fish fins and scales can shed settling mussels, a fish tag offers a suitable substrate. Lychwick said that more walleye than northern pike have been tagged in Green Bay, yet no similar mussel-covered walleye tags have been reported. The WDNR will attempt to verify similar reports. Lychwick would appreciate information from other biologists using similar fish tags in zebra mussel-infested waters. ID: 199406-4. Michigan Inland Lake Monitoring Planned As part of a program funded by Michigan Sea Grant and the Michigan Department of Natural Resources, plankton samples from 45 Michigan lakes will be examined this summer for zebra mussel veligers. Program coordinator Paul Marangelo will train volunteers at an additional 12 lakes to collect plankton samples for analysis. Additional inland lake monitoring will take place this fall. Marangelo is looking for volunteers from inland lake associations willing to inspect boats removed from the lakes. Last summer, researchers discovered veligers in 10 lakes. Since it is not known whether mussel populations have become established in most of those lakes, follow-up observations will be conducted. Lake associations interested in volunteering can contact Marangelo at (313) 994-3331, ext. 297. ID: 199406-5. War of the Sponges MONTREAL, Quebec -- To judge by some recent newspaper headlines, freshwater sponges are taking on zebra mussels -- and winning. The "Chicago Tribune," for example, declared that it's "High Noon for Zebra Mussels," running a sub-headline that read, "Sponges are gunning for pesky mollusk in Lake Michigan, Erie." The gist of the story was that freshwater sponges have been found in abundance at several Great Lakes locations attached to, and covering, zebra mussels. The story implied that freshwater sponges could conceivably help solve current zebra mussel proliferation problems by killing the mussels. McGill University's Anthony Ricciardi, author of a 1993 "Canadian Journal of Zoology" review of sponge taxonomy, distribution and ecology for eastern Canada, has been studying sponge/zebra mussel interactions for several years. He provided "ZMU" with the following comments on these newspaper reports: "(1) Regarding the overgrowth of dreissenid mussels by sponges and its potential impact. Freshwater sponges in the St. Lawrence River (primarily Eunapius fragilis and Ephydatia muelleri) overgrow zebra and quagga mussels on canal walls, rocky substrates, woody debris, and occasionally on unionid bivalves. Mussels may be completely overgrown by E. fragilis as early as June; mussels on canal walls and other permanent substrates may remain covered with sponges for six months or more, and appear to suffer adverse effects due to this fouling. "Despite their competitive ability, it is very unlikely that sponges will significantly reduce dreissenid mussel populations on a large scale, although they may outcompete them on a local scale (e.g., on a canal wall). Dreissenids apparently have no mechanism to prevent fouling and overgrowth, but their high recruitment rate would prevent them from being displaced from a habitat. "(2) Regarding observations of increased sponge abundance in the Great Lakes. Reported increases in the numerical density of sponge colonies are meaningless. A large sponge may fragment to form several independent colonies. Estimates of percent coverage or biomass per unit area are more ecologically relevant measures of sponge abundance and would provide a better idea of whether sponge growth is increasing. "(3) Regarding the notion that 'sponges need clean water.' This statement is misleading. While some species are noticeably absent from heavily polluted waters, others are tolerant of highly eutrophic conditions -- even waters with high coliform levels or high levels of siltation. Some species can tolerate dissolved oxygen levels as low as 0.8 mg per liter." Ricciardi also noted that the sponge genus Spongilla (perhaps featured in newspaper articles because the name sounds like the movie monster Godzilla) is not a likely variety of sponge to harm zebra mussels. Ricciardi is currently preparing his observations of sponge/zebra mussel interactions for journal publication. ID: 199406-6. Quagga Found in the Ohio River CINCINNATI, Ohio -- A single quagga mussel (Dreissena bugensis) was collected last October from the Ohio River, according to Alex Brence and Michael Miller of the University of Cincinnati. The medium-sized mussel was 9.85 mm long and weighed 0.0909 g. Brence and Miller have not collected additional quagga mussels in this area. Since this is the first quagga mussel reported from the Ohio River, Miller said it's unclear whether quaggas have become established in the Ohio River, or whether a single mussel was transported to this location (e.g., via barge movement.). ID: 199406-7. More Cold Veliger Reports BUFFALO, N.Y. -- Zebra mussel veligers were regularly detected throughout the winter in water samples collected from the Niagara River, according to Garry Smythe, Environmental Technical Director for Acres International Corp. Veligers were found in nine of 14 samples collected by the Erie County Water Authority (ECWA) between December 2, 1993, and February 23, 1994. Densities ranged from 14 to 920 per cubic meter. Water temperatures observed during collections ranged from 44 F (6.7 C) to 32 F (0 C). Smythe reported a similar observation of veligers at cold temperatures from samples taken at New York Power Authority facilities in Lewiston, which is located several miles downstream from the ECWA sample station. Live and dead veligers were found in three of four samples taken at 32 F (0 C). Jerrine Nichols of the National Biological Survey said veligers found in cold water are most likely produced by adult mussels living in heated discharge waters from power plants or other warm industrial outfalls. It's unlikely that mussels can spawn at such low temperatures, she said. ID: 199406-8. Mussels Depleting Oxygen in Rivers? HAVANA, Ill. -- Zebra mussels may be depleting oxygen levels in the Illinois River, according to Richard Sparks, an aquatic ecologist with the Illinois Natural History Survey. Sparks reported his research findings at the annual meeting of the American Association for the Advancement of Science. His research is also summarized in the March 4, 1994, issue of "Science." Sparks said aquatic life is stressed when oxygen levels fall to less than 5 parts per million. Levels as low as 3.2 have been found in Illinois River areas heavily infested with zebra mussels. "One of the most dramatic effects is that zebra mussels could wipe out native species of mussels and snails," Sparks said. The oxygen depletion could also lead to reductions in permitted levels of oxygen-depleting organic wastes that are dumped into the river by sewage treatment plants and other waste dischargers. Oxygen depletion has also been observed in New York's Seneca River following a major infestation by zebra mussels. ID: 199406-9. Keywords: Biological_control, Inland_lakes/rivers, Quagga_mussels |