While the Department of Natural Resources continues to investigate a recently-discovered infestation of adult tapeworms in walleye caught on the east side of Michigan, fisheries officials said that the parasite poses no threat to public health as long as the fish are cooked properly.

Walleyes infested with the long, white worms in their digestive tracts have been reported from the Detroit River, Saginaw River, Saginaw Bay, Tittabawassee River, Tawas Bay and the Pine River.

"While the worms are unsightly, they pose no threat to humans as long as the fish are thoroughly cooked before being eaten," said DNR Lake Huron Basin Coordinator Tammy Newcomb. "Tapeworms are a common parasite of many fishes. The life cycle is complicated, and various life stages of the worm live in tiny invertebrate animals, which are eaten by small fish, including many species of minnows. The minnows, in turn, are eaten by larger predatory fish, including walleye."

Newcomb said the tapeworm develops into the adult stage in the walleyes. Eggs are shed in the feces, and the lifecycle repeats itself. Some tapeworms also infest warm-blooded animals, including humans, primarily through the consumption of uncooked food.

"Normal cooking, smoking and pickling processes will kill all parasites found in fish flesh," said Jim Baker, DNR manager for the Southern Lake Huron Fisheries Unit. "Under no circumstances should anyone be consuming raw fish. Sushi made from freshwater fish is definitely a bad idea."

Baker said the DNR will continue to investigate this new infestation to determine the exact species and life cycle of the parasite, and to learn why it is suddenly showing up in walleye.

Fisheries biologists believe that walleye are becoming infested with the worms because of recent changes in their diet due to the collapse of alewife populations in recent years. Alewives once comprised the majority of the walleye's diet, but in their absence, walleyes are eating large numbers of young yellow perch, round gobies, gizzard shad and minnows.

Despite the infestation, walleye fishing on inner Saginaw Bay was thriving until a recent cold front moved into the area, Baker noted. Anglers were having no problems catching fish and limit catches were reported everywhere from Linwood south and east to Quanicassee when trolling with planer boards or drifting crawler harnesses. The early season success in the fishery is forecasted to continue through the summer, Baker said.

"One of the reasons for this tremendous success in the fishery is believed to be the lack of alewife that compete and prey upon young life stages of walleye and perch," Baker said. "Walleye have been naturally reproducing at record levels for the past four years, providing large numbers of young fish that are now being caught in the recreational fishery."

For more information on fishing in Michigan, visit the DNR's Web site at www.michigan.gov/dnr and click on the Fishing menu.