|
|
|
Kraft, C., JANUARY, 1996. Zebra Mussel Update #26, University of Wisconsin-Madison, Wisconsin Sea Grant Institute A Newsletter produced by the Wisconsin Sea Grant Institute Zebra Mussel Update #26Inland Lake Sightings: A Tale of Two States Michigan inland lakes are becoming more rapidly colonized than Wisconsin lakes, according to the results of a cooperative project supervised by Ladd Johnson (Universite Laval) and Clifford Kraft (University of Wisconsin-Madison), with assistance from many cooperating individuals and agencies. The comparison showed a different pattern developing in each state. By the end of 1995, adult or larval zebra mussels had been confirmed in 33 inland Michigan lakes, five more than at the end of the previous year. Adult zebra mussels had been confirmed in 21 Michigan lakes; veligers had been detected in the other 12 lakes. Unconfirmed adult sightings had also been reported from an additional five inland lakes. Wisconsin sightings have been scarcer than in Michigan. Adult or larval zebra mussels had been detected in seven inland Wisconsin lakes by the end of 1995, three of which were new sightings. In total, four Wisconsin lakes had confirmed adult populations; the other three lakes had veligers. No unconfirmed adult sightings have been reported from Wisconsin lakes. It is unlikely that the observed differences in inland lake sightings are due to sampling differences because the sampling efforts were similar in both states. Rather, Johnson and Kraft speculate that the abundance of submerged macrophytes in source waters may be responsible for the different pattern in each state. In earlier work, Johnson noted that submerged macrophytes with attached zebra mussels were often found hanging on boats and trailers being removed from zebra mussel-infested Lake St. Clair. The abundant macrophyte growth in Lake St. Clair could have contributed to the rapid spread of mussels to inland Michigan lakes. To date, Lake Michigan, which is relatively free of macrophytes, has been Wisconsin's primary zebra mussel source. Unfortunately, this could change now that several macrophyte-rich inland Wisconsin lakes are infested and have become potential sources for further inland lake colonizations. ID: 199601-1. St. Croix River Infested? When is a body of water truly "infested?" Minnesota DNR Ecological Service Section's Gary Montz recently wrote ZMU requesting help from the zebra mussel community to define the term. Montz wrote: "A number of agencies in Minnesota and Wisconsin are trying to keep the zebra mussel from spreading into the St. Croix National Scenic Riverway, which is home at last count to over 40 species of unionids, including the Winged Mapleleaf. The St. Croix is a tributary to the Mississippi River below the Twin Cities, and supports a tremendous amount of recreational boating traffic in the lower 26 miles. Above that area, the river becomes much shallower and boating traffic decreases. "The problem in trying to stop the zebra mussel arises from the boat travel between the Mississippi and St. Croix rivers. Additionally, this lower part of the St. Croix includes border waters managed by both Minnesota and Wisconsin, with federal agencies such as the USFWS, National Park Service and Coast Guard having additional responsibilities. "Actions the Minnesota DNR might take depend on whether the river is officially 'infested' or not. Certain laws apply to uninfested waters, while others only apply to waters infested with exotic species. We also have specific signs for access sites on infested waters. "Together with the other agencies working on the zebra mussel issue, we need to determine if the St. Croix River should be declared 'infested.' However, there are widely differing opinions on what determines infestation. "I would appreciate input from on some of the following issues: 1. How would you determine when a river (or lake) is 'infested' with zebra mussels? Do specific densities need to be reached? Do you need evidence of reproduction? Or is the presence of zebra mussels on multiple fixed substrates (bridge piers, rip-rap, etc.) sufficient to assu me infestation? What about multiple size classes attached to river substrate? 2. If evidence of reproduction is necessary, what level of sampling is necessary in a large river system to document this event? Should plankton samples or mesh samplers be used, or settling plates? Is any sampling likely to catch reproduction in the early stages? 3. Should we be looking at intermediate stages before calling something infested? For example, should we be telling people that we have found attached zebra mussels, but no evidence of reproduction, and that we are waiting for this to declare infestation? 4. What about remediation to prevent or slow the infestation of zebra mussels? Is having divers physically remove mussels from river substrates a viable option? Or is this a gesture as futile as trying to bail out the ocean with a bucket? Is there a density at which this might make sense? Has this been tried in any form elsewhere and, if so, what happened? "Please send comments to me via email: gary.montz@dnr.state.mn.us. You can also fax me at (612) 296-1811, or call (612) 297-4888. I'd also like to try and organize an informal session at the 6th Zebra Mussel Conference to discuss these topics.". ID: 199601-2. Carp Feast on Zebra Mussel in Mississippi There was widespread media attention this fall about common carp feeding on zebra mussels. (See Cliff's Notes for more on the subject.) The stories were inspired by the findings of John Tucker, a biologist with the Upper Mississippi River Long-Term Resource Monitoring Program in Alton, Ill. Given all the hoopla, we contacted Tucker and he sent this intriguing response: "I was fishing with my daughter near Brussels Ferry, Ill., this summer when we caught a common carp 290 mm long. To satisfy my daughter's curiosity, we took it home to dissect. When we examined it, we found that the fish's gut was completely packed with fragments of zebra mussels. "Because the common carp had not been reported to feed extensively on zebra mussels in the United States, I asked station biologists to collect carp from the Mississippi River, just below the confluence with the Illinois near Grafton, Ill. This collection site has been monitored for zebra mussels since 1992 and is known to be heavily colonized by them. "Of the 31 common carp examined (ranging in size from 243-559 mm), 26 contained the remains of one or more zebra mussels. With few exceptions, the zebra mussel shells were crushed and well fragmented by the carp. Staff members determined the number of zebra mussels present in each gut by halving the number of internal septa found. The number of zebra mussels consumed ranged from 0 to 204. Measurements are incomplete at this time, but the largest carp contained specimens of zebra mussels estimated to have been 15-18 mm in shell length, based on septa lengths. Smaller fish contained zebra mussels estimated to be less than 12 mm in shell length." Tucker said he publicized his initial findings because some aquaculturists have suggested releasing other exotic carp species to control zebra mussels. Substantial common carp predation further diminishes the rationale for introducing another exotic carp to prey on zebra mussels, he said. Moreover, predation evidence can be collected without killing the fish by expressing feces from the vent of the carp. The feces can then be examined for zebra mussel shell fragments. Further investigation into the phenomenon appears warranted, agreed Steve Gutreuter, director of monitoring and research at the National Biological Service Environmental Management Technical Center in Onalaska, Wis. "It is far too soon to tell whether carp might help control zebra mussel populations," he cautioned. "The fact that zebra mussels and carp are both abundant in some areas of the upper Mississippi River suggests that carp are unlikely to be controlling the densities of zebra mussels. However, in areas where zebra mussels may already be limited by lack of suitable conditions, the additional mortality from carp predation might be important.". ID: 199601-3. DNA Probe to Detect Veligers Developed A new technique to detect larval zebra mussels is close to being developed by a research team at Rensselaer Polytechnic Institute (RPI). Sandra Nierzwicki-Bauer, chairwoman of biology at RPI and director of RPI's Darrin Fresh Water Institute, and postdoctoral research associate Marc Frischer are investigating the use of DNA genetic probes to test for the presence of zebra mussel veligers. The project was initiated in September 1994, with a $112,000 grant from New York Sea Grant. The most common technique for identifying zebra mussel veligers requires examining water samples under a stereo microscope equipped with cross-polarized light. By using the new DNA genetic probe, which still requires a microscope, the identification process will be much quicker and allow more water samples to be tested, Frischer believes. Using the new technique will not require the expertise of a highly trained scientist, he said. The researchers have already completed the first step of the project, which involved identifying a portion of the mussel's genetic makeup and a sequence of 1,800 segments. A probe is now being created that will link to only the RNA of the zebra mussel. The probe is a combination of a piece of DNA synthesized to match the sequence of the zebra mussel and a "reporter" molecule. Veligers will appear colored when the probe attaches to them. "This will allow us to get very sensitive detections, higher than what can be done right now microscopically, and has the potential of being automated," Frischer said. "The genetic approach is also providing information about the zebra mussel's evolutionary history which improves our basic understanding of this animal. We see our next steps as using the probe to study more of the ecology, the larval ecology, what happens to the veligers - how they move, mortality factors - and things we don't really have the answers to," Frischer said. - Judith N. Hogan, New York Sea Grant. ID: 199601-4. The Great Cover-up A marine heritage preservation group in Kingston, Ontario, is currently undertaking a project to photographically record a number of local historic shipwrecks being colonized by zebra mussels. Jonathan Moore, a marine archaeologist and member of the group "Preserve Our Wrecks (Kingston)," is concerned not only with the masking of submerged archaelogical resources by zebra mussels, but also that stripping zebra mussels from the surfaces of these resources will result in damage and the loss of important information. "Byssal threads of the mussel invariably pull off fragments of the material to which they are attached," Moore said. "Repeated cycles of mussel attachment and removal might result in serious damage to the surface of the site. "The lakes, rivers and minor water bodies of North America contain rich archaeological resources from historic shipwrecks to prehistoric habitation sites. These benign freshwater environments can preserve archaeological resources for centuries. The introduction of the zebra mussel to these environments is a challenge to archaeologists and preservationists as zebra mussels attach themselves to historic structures and artifacts." The initial impact of zebra mussel attachment is the loss of "archaeological visibility" - the surfaces of a historic shipwreck can literally disappear under layers of mussels. "Like an historic building covered in ivy, we can recognize its shape, but details of its surface and construction are obscured," Moore said. "If we cannot see, recognize, accurately measure and examine diagnostic features of a shipwreck (i.e., steering mechanisms, machinery, hull construction or fastenings) free of mussels, our ability to study the site is dramatically impacted. The dilemma we face is that the removal of mussels to expose the sources of the site is potentially destructive." Moore would like to hear from others with similar concerns. He can be contacted at Marine Museum of the Great Lakes at Kingston, 55 Ontario St., Kingston, Ontario, Canada K7L 2Y2, or reached via email: jmoore@limestone. kosone.com. ID: 199601-5. Zebra Mussels in the Illinois River: Here Today, Gone Tomorrow? A mysterious new chapter was written in 1995 in the ongoing Illinois River zebra mussel saga. Almost no mussels were found this fall in the lower 120 miles of the river. In October, Illinois Natural History Survey (INHS) biologist Scott Whitney sampled sites in the area and found less than one gallon bucket of live zebra mussels. Whitney had found abundant mussels at these sites earlier this summer. "In 1993, our divers were collecting five gallons in five minutes at these same sites," INHS biologist Doug Blodgett said. "We were afraid we'd find something similar this fall." Instead, Whitney found piles of zebra mussel shells, almost all of which were empty - evidence of another significant die- off. INHS biologists observed a zebra mussel population boom during surveys conducted in 1993. These populations radically declined in late 1993 and 1994 along the lower 120 miles of the river, the area regularly surveyed by INHS biologists. "High mortality with densities at one site dropped from over 60,000 per square meter in summer 1993 to less than 600 per square meter by fall 1994," Blodgett said. Another expanding population had been expected earlier this year. "It's obvious zebra mussels were doing well somewhere upriver earlier this year because we calculated over 60 million veligers per second drifting by our station on a couple occasions," Blodgett said. 1995 continued to look like a big mussel year when divers found small, newly settled zebra mussels in densities of 1-5,000 per square meter in July. But between July and October something happened. Sporadic episodes of poor water quality - low dissolved oxygen, heavy silt loads and high water temperatures - could be responsible, Blodgett speculated. As long as reproducing zebra mussels persist upriver, the lower Illinois River will be vulnerable to continuing boom and bust cycles, he believes. - Robin Goettel, Illinois-Indiana Sea Grant. ID: 199601-6. Building New Barriers? A small group of state and federal agencies and Great Lakes organizations recently explored alternatives to prevent the transfer of exotic species from the Great Lakes to inland water systems. The Nov. 20 meeting, "Introduction Pathway of Exotics to Inland Waters of the U. S. Chicago Sanitary and Ship Canal," was sponsored by the U.S. Fish and Wildlife Service and the U.S. Army Corps of Engineers-Chicago District. Zebra mussels originally gained access to many U.S. inland waterways through the Chicago Sanitary and Ship Canal connection between Lake Michigan and the Mississippi basin. Major conference concerns included identifying a barrier that would stop nuisance species such as ruffe, round goby and zebra mussels from reaching inland waters, and controlling the spread to the Illinois River. Eurasian ruffe is expected to make its way inland unless barriers are erected to block its movement. Discussions included adding exotic species control devices to the Chicago Sanitary and Ship Canal system. Attendees also noted that the Chicago Sanitary and Ship Canal poses a hazard by allowing non-native species (such as nonindigenous zooplankton) to enter the Great Lakes. For further information contact Jay Troxel, Aquatic Nuisance Species Coordinator for the U.S. Fish and Wildlife Service, phone, (703) 358-1718. - Robin Goettel, Illinois-Indiana Sea Grant. ID: 199601-7. New Publications: Zebra Mussels and Aquaculture "Zebra Mussels: A Crisis in Aquaculture" is a new four-page pamphlet discussing potential problems zebra mussels can cause for aquaculturists. Written by North Carolina State University Extension Fisheries Specialist Jim Rice, the pamphlet provides suggestions for protecting aquaculture water supplies and discusses ways to prevent the contamination of water used for hauling fish and fingerlings. Other topics include the use of disinfectants, control measures for infested facilities, and the implementation of inspection and monitoring programs to detect the presence of zebra mussels. The publication is available from North Carolina Sea Grant, P.O. Box 8605, North Carolina State University, Raleigh, NC 27695-8605, phone (919) 515-2454, email: harriss@ unity.ncsu.edu. ID: 199601-8. Zebra Mussels Make Top Ten List of Worldwide Trends A Worldwatch Institute mail solicitation recently identified "Ten Key Findings" from the State of the World 1996, including the following: "Economic costs of the introduction of exotic species such as the Zebra mussel [sic] in the U.S. Great Lakes are adding up to billions of dollars each year, and will likely increase, creating a drag on the region's economy.". ID: 199601-9. Zebra Mussels Make Top Ten List of Worldwide Trends A Worldwatch Institute mail solicitation recently identified "Ten Key Findings" from the State of the World 1996, including the following: "Economic costs of the introduction of exotic species such as the Zebra mussel [sic] in the U.S. Great Lakes are adding up to billions of dollars each year, and will likely increase, creating a drag on the region's economy.". ID: 199601-9. Zebra Mussels Found in Geneva Lake Adult zebra mussels were found on three different occasions this fall in Walworth County's Geneva Lake, according to officials at the Geneva Lake Environmental Agency. The first sighting occurred in October. About a dozen adult zebra mussels were found attached to a dry-docked boat at Gage Marine. The boat had been moored near the city of Lake Geneva boat launch site, which is near the Geneva Lake outlet to the White and Fox rivers. Following confirmation of the initial sighting by Wisconsin Department of Natural Resources (DNR) and UW Sea Grant staff, a lone zebra mussel was recovered from the lake during a scuba survey. Later in the fall several other mussels were reportedly found during removal of piers along the shoreline, according to Geneva Lake Environmental Agency's George Johnson. Geneva Lake is a large (5,400 acre), heavily used recreational lake close to metropolitan Chicago and Milwaukee. The lake generally does not contain a lot of macrophytes due to its deep configuration. Once known as "The Newport of the West," and now promoted with the slogan "Enjoyed for 100 Years by the Rich and Famous," Geneva Lake had 4,500 resident boats in 1995, 60 percent of which were over 21 feet long, according to Johnson. In 1994 almost 20,000 boat launches occurred at lake ramps, suggesting great potential for spreading mussels to other inland lakes. ID: 199601-10. Zebra Mussels in Lake Winnebago? Lake Winnebago may be infested. A boat moved to Oshkosh in August transported zebra mussels from Green Bay to the upper Fox River a few miles from where the river enters Lake Winnebago, Wisconsin DNR officials reported in October. Two adult zebra mussels and a dozen smaller zebra mussels were found in part of the inboard/outboard drive system of a boat taken out of the Fox River, according to DNR fisheries biologist Lee Myers. Because Green Bay is infested with zebra mussels, it's likely the mussels were picked up there, Myers said. This is the first detection of zebra mussels in the Lake Winnebago system. "The adult mussels appeared to be alive, and the boat was in the Fox for about two months," Myers said. "But we had no way of knowing if the adults reproduced during that time." Lake Winnebago is home to an estimated 25 million freshwater drum and 40,000 lake sturgeon larger than 45 inches, both of which consume native fingernail clams, according to DNR fisheries biologist Ron Bruch. "Winnebago will be a good test case of whether fish predation can limit zebra mussel populations," Bruch said. ID: 199601-11. Filtering the Flow As You Go Although many companies have created products for preventing zebra mussel infestations, one boat manufacturer has devised a product designed to help prevent recreational boaters from spreading them to new locations. MirroCraft Boats is marketing an environmentally friendly recreational boat that comes with a filtration system designed to remove zebra mussel veligers from "live well" intake water. Wisconsin boater advisory guidelines recommend that water in the live wells of recreational boats be drained when moving from one lake to another to avoid transporting veligers. Company vice president Dan Boettcher said the live well pump intake system includes afilter that should remove particulate material less than 30 microns in size. Wisconsin Sea Grant staff plans to test the effectiveness of this system next summer. ID: 199601-12. Mussels in the Mighty Miss' Since zebra mussels were first found in the Mississippi River near La Crosse, Wis., in 1991, the population has grown much denser and become more widely distributed. Densities in the Minnesota stretch of the Mississippi River are highest at the southern end of Lake Pepin, near Red Wing, Minn., according to Minnesota Department of Natural Resources fisheries biologist Mike Davis. The highest densities approach 5,400 per meter square, averaging well over 1,700 per square meter at some locations. Zebra mussels are found everywhere downstream from there, according to Davis. "I've found specimens up to 50 mm long, with many about 20 mm long," he said. "In many areas, the average size of last year's cohort is about 10 mm." Zebra mussels are also found at every lock and dam north of Lake Pepin. Infestations are not as dense because veligers drifted farther downstream before settling, Davis speculated. What impacts are zebra mussels having in the river? First, the infestation is causing industries using Mississippi River water to implement on-line control strategies. In addition, a team of natural resource agencies, led by the U.S. Fish and Wildlife Service, has moved hundreds of unionid mussels from the river to save them from becoming encrusted with zebra mussels. The unionids will be temporarily held in experimental ponds at the Genoa Fish Hatchery south of La Crosse. If unionids can be successfully maintained in hatchery ponds, more river specimens will be moved; if an effective control can be developed or if the infestation eventually subsides, the native unionids will be returned to their native habitat. At least five recreational boats suffered problems during the 1995 boating season because zebra mussels clogged their engine cooling systems, according to John LaRocque of Northport Marina in Alma, Wis. "Two engines were wrecked completely," LaRocque said. "Three others experienced overheating, but suffered no damage. Another boat that came up river from Iowa had so many zebra mussels on the outdrive it couldn't be turned to the right." Mussel-caused nuisances weren't exclusive to boaters, either. Anglers reported that their lines had been cut by the mussels' sharp shells, the Minnesota DNR's Davis said. - Doug Jensen, Minnesota Sea Grant. ID: 199601-13. Cliff's Notes I knew something was up when he called across the locker room, "Hey, I heard on the radio that carp are going to get rid of your mussels." Moose is always ahead of the curve. A former professional baseball player, Moose and I talk about two things - zebra mussels and sports - and this conversation wasn't going to be about my pitching arm. Moose always alerts me when the public is getting a new zebra mussel-related pitch. Two years ago it was sponges. Before that it was red pepper in paint. Now it was carp. And once again, Moose was right. Within a week the story was in the local paper. Within a month it was in Newsweek, accorded the same importance as Yeltsin's health and Bosnian peace talks. It's amazing how quickly public attention is drawn to stories of salvation and harmony in nature. Zebra mussels being eaten by carp: nasty new immigrants getting beat up by the fish Americans love to hate. While the subject has merit (see related item in this newsletter) and deserves further exploration, the media should have taken a seventh inning stretch until more research is done. Madison's Wisconsin State Journal was so taken by the topic that a Sunday editorial concluded that "next time you catch a carp, don't kill it - toss it back. You just might be firing an important shot in the war against zebra mussels." In the spirit of Charley Brown, my only response is "Augghhhhh!!!!" I'm going to stick with the sports pages - until I can figure out how to fire an important shot in the war against stupid zebra mussel stories. ID: 199601-14. Keywords: Inland_lakes/rivers, Population_dynamics, Predators |