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Tue August 2, 2011
Sea lampreys gaining the upper hand
For fifty years Canada and the U.S. have been battling an eel-like creature across the Great Lakes. Sea lampreys are parasites that drill holes in fish to feed on blood and body fluids. They often kill the fish. The sea lamprey was one of the first invasive species to arrive in the lakes, and it’s the only invasive to be successfully controlled by humans.
But in recent years, the lamprey has been getting the upper hand in the struggle. As Peter Payette reports there might be more setbacks in the near future:
If you’re on a lamprey control team you get to see all the prettiest streams and rivers in the Great Lakes. That’s because lampreys like clean water.
“Part of our problems recently have been some of the streams that were too dirty to harbor lampreys have been cleaned up and now we have lampreys in parts of the Saginaw River. We never had lampreys in that up until 15 or 20 years ago.”
Ellie Koon supervises one of the U.S. Fish and Wildlife treatment teams. They spend the warm months killing young lampreys by the thousands.
They treat rivers using a chemical called lampricide. It’s a poison that rarely hurts other fish. In fact, during a treatment the fish get a feast they normally wouldn’t. Young lampreys look a bit like worms at this stage and stay in the mud. But when they’re poisoned they swim out where fish can grab them.
Ellie Koon and one of her team members, Hank Cupp, say fish and other animals in the river pig out.
“You can almost hear the fish burping the day after we treat. You can see them swimming around with lampreys hanging out of their mouths that they can’t swallow.”
These teams can usually kill about 95 percent of the young lampreys in a river. Without this, the Great Lakes would not have a multi-billion dollar fishery today. But in recent years, the fish-killing lamprey has been rebounding in some of the lakes and hurting the fishery.
Jeff Slade manages the U.S. Fish and Wildlife Biological Station in Ludington. He says these days in northern Lake Michigan they think one out of every four adult lake trout is killed by a lamprey.
“So sea lampreys are actually killing many more fish up in that part of the lake than fishermen are harvesting.”
The problem varies from lake to lake, but lamprey numbers are high in Lakes Huron, Michigan and Erie.
One reason is a decision made nearly a decade ago. That’s when the commission that oversees this work wanted to cut back on the amount of chemicals being used. So for a few years, U.S. Fish and Wildlife teams used the minimum amount of lampricide believed to be necessary.
That turned out to be a mistake and has since been changed.
Scientists like Mark Ebener think the reduction of lampricide treatment is the main reason sea lampreys have rebounded. Ebener’s a fisheries biologist for the Chippewa Ottawa Resource Authority.
“I think the thing we know is that the minute you relax chemical control you lose control. As unfortunate as that is to people who want to rely less on chemicals.”
And now the prospect of a budget cut looms over the lamprey program. President Obama’s proposed budget would cut funding by 15 percent.
Marc Gaden is with the Great Lakes Fishery Commission. It’s his job to tout the importance of the federal funding. Gaden says there will be a direct connection between less money to fight sea lampreys and real harm to the fishery.
“Each lamprey will destroy about forty pounds of fish during its predatory period, forty pounds! You can just kind of do the math… even if you leave a few ten thousand more lamprey in the system, that’s a lot of fish they’re going to be eating.”
Some budget cuts could fall on more experimental parts of the program, projects like developing special scents to draw adult lamprey into traps. That would leave in place the main weapon in the endless fight against sea lampreys, chemical treatments.
-Peter Payette for The Environment Report