Summer/Fall 2006


The hungry mouths of sea lamprey. Photo: Great Lakes Fishery Commission

UW Sea Grant Research

A Passage for Boats, a Barrier for Invaders

By John Karl

The historic Fox River passage between Green Bay and Lake Winnebago has been closed to boat traffic since the U.S. Army Corps of Engineers shut down most of its 17 locks in 1988. Now, the State of Wisconsin is working to make the waterway navigable again — but to deny passage to the many exotic species that the closed locks have kept out of Lake Winnebago. The Corps transferred operation of the locks to the State of Wisconsin in 2001 (although the Corps continues managing water flow rates). The state then created the Fox River Navigational System Authority (FRNSA) to open 16 of the locks. The Rapide Croche lock, near Watertown, will remain permanently closed so that sea lamprey and other alien organisms can not simply swim upstream into Lake Winnebago and threaten its prized walleye and lake sturgeon fisheries.

That means boats will have to be moved around the lock, and they must be thoroughly cleansed of all exotic species: no zebra mussels clinging to the hull, no sea lamprey larvae hiding in bait wells. Even microscopic eggs of water fleas, which can hide in the tiny passages of bilge pumps or engine cooling systems, must be flushed out.

That’s a tall order, and UW Sea Grant Invasive Species Specialist Phil Moy is helping meet the challenge. Moy is a member of the FRNSA’s Committee on Invasive Species. He has suggested using the lock chamber as a hot water bath and soaking boats in it to rid them of unwanted – and even unseen – exotic species.

Moy has outlined some details of how such a process might work. The first step would be to remove all live fish and bait from buckets and live wells. Boats would then be lifted out of the water with a forklift, hoist, or other mechanism. While out of the water, their hulls will be visually inspected. They would be turned away if they are excessively encrusted with algae or other organisms. If not, the boats would be set in the lock chamber.

The water would be heated to 145º F. Studies show that contact with water at 145º F for two minutes kills the eggs and larvae of all exotic species currently known to threaten Lake Winnebago.

While in the hot water, engines and bilge pumps could be run to flush out their internal passages with the heated water. Live wells and bilges might be sprayed. Fishing rods, skis, ropes, anchors and other equipment that can harbor eggs or larvae would be placed in mesh bags and soaked in hot water for two minutes.

Only boats moving upstream (i.e., southbound, from the Green Bay side of the barrier toward the Menasha side) would be treated. Because Lake Winnebago contains no exotic species that threaten Green Bay, there’s no need to clean boats moving downstream.

Moy stressed that these ideas are in the very earliest stages, and people will have “lots and lots and lots” of opportunities to comment on plans as they develop. Both the FRNSA and the Friends of the Fox River will solicit comments, and the Wisconsin Department of Natural Resources will hold official hearings. These will be conducted after preliminary ideas are assessed, Moy said, which could be “several years” from now.

The committee has hired STS Consultants, Ltd., an environmental engineering firm, to estimate the costs and identify any environmental concerns that a lift-and-soak operation might raise.

Whatever solution is eventually found for the Rapide Croche lock, the work of implementing it will be funded with a combination of private donations and state and federal funds, Moy said. It will also be only part of the total effort needed to keep Lake Winnebago free from the invasive species lurking in nearby waters, he added. Moy notes that there are 48 boat ramps around Lake Winnebago, and all are potential entry points for invasive species. He says boaters need to be aware of the importance of thoroughly cleaning off their boats or leaving them out of water for 24 hours when they go from lake to lake. He says such vigilance, combined with the efforts at the Rapid Croche barrier, can protect the fisheries of Lake Winnebago while once more enabling travel along the historic lower Fox River.









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