Predators in Residence — Fall 1996
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The Great Lakes… 84% of the continent’s fresh water… a different story in every drop.
Author: Carol Johnson
Canada’s decision to reduce funding for lamprey control during 1996-97 by 26 percent may threaten the Great Lakes Fishery Commission’s ability to start sea lamprey control measures on the St. Marys River according to fishery managers from Michigan, Ontario, and the tribes during a meeting of the Lake Huron Committee in Duluth. The St. Marys River, largest single source of sea lampreys, is vital to the health of the Lake Huron Fishery. Spawning age lamprey numbers in northern Lake Huron are thought to be larger than all other Great Lakes combined with the total population of the St. Marys nearly as large as before any eradication efforts were attempted. Some 45 percent of Lake Huron’s trout and salmon carry wounds or scars from lamprey attacks while 29 percent of lake trout in northern Lake Michigan show scars from St. Marys River lamprey.
Before the funding cuts and after many years of planning, the Great Lakes Fishery Commission was about to implement a St. Marys River lamprey control program.
However, the U.S. Fish and Wildlife Service released some 20,000 sterilized male sea lampreys into 27 Lake Superior streams during the spring of 1996. Included in the release areas were the popular fishing rivers, the Waiska River and the Two Hearted River, both in the eastern Upper Peninsula. Sterilized male lampreys spawn with the females but the eggs are not fertilized and the males die after spawning. Fertile female eggs produced in each stream are reduced by about 65 percent. The program is a supplemental control method to lampricide treatments and is not intended as a replacement for existing chemical measures.
Exporting A Problem
While the Michigan Department of Natural Resources and other interested parties continue to attempt to eradicate the sea lamprey in the Great Lakes, another possibility has sailed over the horizon – exporting lampreys to Portugal. The Portuguese consider them a delicacy at up to $25 per pound. The Minnesota Sea Grant in Duluth will ship 1,000 sea lampreys to Portugal during the summer of 1996 when Portuguese taste testers will compare them to their own sea lampreys, which are in short supply. According to a panel of gourmet tasters in Duluth, lamprey tasted somewhere between liver and seaweed. A lamprey dish is prepared by first cutting the head off a live one, then draining and seasoning its blood. The body is chopped up and cooked in blood and spices. According to Duluth restaurateur Bob Bennett, chef for the taste test, things got interesting when many of the 15 lampreys on the menu slithered away and attached themselves to a stainless steel sink with their suction mouths.
On Another Front
While spring took its time reaching the Lake Michigan shores, unfortunately the alewives did not. They washed up onshore in massive numbers for the second time in two years. Last year saw the first massive die-off in many years and 1996 was even worse. The Port Authority in Michigan City, Indiana, hired two employees to work eight to ten hour shifts, seven days a week to remove dead fish from the water as they drifted into the harbor from Lake Michigan. Fish that made it to shore were removed with wheelbarrows and shovels. Despite wages of $9.60 per hour, there was a high turnover of employees.
Stalking The Zebra
While more studies need to be done, preliminary work by the Ohio Environmental Protection Agency has shown the round goby, one of the few known predators of the zebra mussel, may not be as beneficial as first thought. The round goby, a three to six inch long fish, has also become a diet staple of the smallmouth bass, a prized Ohio sport fish. Zebra mussels, which may be 80 to 98% of the goby diet in parts of Lake Erie, may each filter a liter of water or algae per day, absorbing PCBs and other chemicals into their fat. When gobies are eaten by smallmouth bass, the PCBs and chemicals have a more direct pathway into the human food chain. A tissue analysis of ten smallmouth bass caught in the Grand River near Fairport Harbor, Ohio found PCB levels of 50 to 218 parts per billion while bass caught in the Huron River near Huron, Ohio had no detectable levels of PCBs.
Scientists from the Sea Grant program and the Stone Lab dropped the shell of a 1969 Volkswagen Beetle, several pieces of patio furniture, a grill, and a tricycle in the water of Lake Erie about 50 yards off the north coast of Gibraltar Island. While the act sounds like litter bugs gone berserk, the scientists were providing hard surfaces for zebra mussels to attach themselves. If all goes as planned, the car and other items will be retrieved from the lake in October and transported, with zebra mussels attached, to New York City. The items will be used in a display during March 1997 in an exhibit of endangered and introduced species at the American Museum of Natural History. Chosen for the display because they have caused so much havoc, the zebra mussels will serve as an example of the problems caused by the introduction of exotic species. First discovered in the Western Basin of Lake Erie on October 15, 1988, the mussels have spread to inland lakes and as far south as New Orleans.
Freshwater sponges may be a new, natural defense against zebra mussels in the Great Lakes according to biologists of Ohio State University and the Great Lakes Environmental Research Lab at Ann Arbor, Michigan. Sponges have been found growing on top of and killing zebra mussel colonies in Lake Michigan, Lake Erie, and the St. Lawrence Seaway. According to David Kelch, fisheries biologist at OSU, the freshwater sponges look like green slimy pancake batter poured over the mussel beds. Unfortunately, sponges seem to grow only on vertical surfaces which limits their range to canal walls, large rocks, reefs, wrecks, and pilings while zebra mussels can attach themselves to any surface.
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