Walleye swimming in Michigan’s largest watershed are 80 percent less contaminated with PCBs than they were in 1997, according to a study published recently in the Journal of Great Lakes Research.

PCBs are toxic, potentially cancer-causing chemicals that were used in electrical insulators, hydraulic equipment and some paints. The U.S. and many other countries banned PCB production in the 1970s and 1980s

PCB levels in Saginaw Bay walleye have dropped 80 percent since 1997, said study author Chuck Madenjian, a fishery biologist at the U.S. Geological Survey’s Great Lakes Science Center. He credits the drop to a dredging project in 2000 and 2001 that pulled more than 340,000 cubic yards of polluted sediment out of the Saginaw River, the bay’s main tributary.

That’s enough to cover a football field in 160 feet of mud.

“This dredging was really effective in bringing down those concentrations to some really low levels,” said Madenjian,

That’s good news for Saginaw Bay’s world-class walleye fishery, said Michelle Selzer, the Michigan Department of Environmental Quality’s coordinator for the Saginaw River and Bay Area of Concern. Areas of Concern are 43 highly contaminated sections of the Great Lakes designated by the U.S. and Canadian governments.

“The fish are our ambassadors,” she said. “They’re telling us something.”

What they’re telling us is that environmental laws like the Clean Water Act that crack down on industrial water pollution are working, she said. The laws aren’t perfect, , but they give environmental agencies a chance to target and clean old pollution hotspots like the Saginaw River’s PCB deposits.

General Motors Corp. factories and municipal wastewater treatment plants dumped PCBs in the Saginaw River beginning in the 1940s, according to the U.S. Fish and Wildlife Service. In 1998, that agency, the state of Michigan and the Saginaw Chippewa Tribe reached a settlement with General Motors Corp. and the cities of Saginaw and Bay City, Mich. to pay for the dredging.

Though the PCBs were dredged nearly a decade ago, this new evidence of cleaner fish is still significant because scooping polluted dirt out of a waterbody doesn’t always mean wildlife gets cleaner, Madenjian said.

“You would expect in general that it would happen, but sometimes you get mixed results,” he said.

A 1997 project that pulled 100,000 cubic yards of DDT-laced sediment out of San Francisco Bay left some fish more contaminated than they were before the dredging.

Madenjian tested fish from the Tittabawassee River, a tributary of the Saginaw River that eventually flows into Lake Huron’s Saginaw Bay. When Saginaw Bay walleye swim upstream to spawn, most head up that river system until they hit a dam on the Tittabawassee River on Dow Chemical Co. property in Midland, Mich., Madenjian said.

“You have the bulk of the spawners from the entire bay being concentrated right there at this Dow dam,” he said.

Dow Chemical is responsible for widespread dioxin contamination in the Saginaw Bay watershed. Dow, Michigan’s environmental agency and the U.S. Environmental Protection Agency recently reached a tentative agreement on a plan for the chemical company’s dioxin cleanup. The plan is open for public comment until Dec. 17.

For the full article, see Jeff Gillies, "Toxic cleanup spurs walleye resurgence", Capital News Service, Week of November 24, 2009.