That?s why a proposal to reopen the Fox River between Lake Winnebago and Green Bay to boat traffic leaves closed the Rapide Croche lock and dam near Wrightstown. The edge of the dam has a lip on it to keep out the lamprey. It also keeps out a growing number of nasty critters that, like the lamprey, are considered invasive species in the Great Lakes ? the spiny water flea, the round goby, the ruffe fish and the white perch.

Some of those creatures are carried by boaters to new territories. The issue of invasive species has prompted a sharp division between fishermen who value Lake Winnebago the way it is, and other boaters seeking more travel options up and down the lower Fox River.

At least three fishing clubs around Lake Winnebago are opposed to the idea of reopening 13 other locks so boats can travel from Green Bay to Menasha and beyond.

"We?re very concerned about exotic species like the lamprey getting in," said Bill McAloon of Oshkosh, a member of the Otter Street Fishing Club. "It?s kind of a touchy subject with fishermen here."

Keeping out the lamprey means a mechanism is needed to lift boats over Rapide Croche. The private group Friends of the Fox has a draft proposal that envisions a 20-minute delay for boaters while their vessel and equipment are inspected, lifted, powerwashed with hot water and, possibly, cleaned with vinegar to kill any unwanted passengers.

The boatlift proposal has the blessing of Phil Moy, a biologist with the University of Wisconsin SeaGrant Institute.

Moy is considered a leading expert on the zebra mussel, an invasive species already at home in Lake Winnebago, most likely because of unsuspecting boaters. He said the boatlift at Rapide Croche may help prevent further spread of the lamprey and its invasive cohorts.

"I?m pretty confident the system they?re going to propose will prevent the spread through the boatlift. I think the real threat is the access by trailered boats," Moy said. "It?s as foolproof as you?re going to get."

That assurance is not enough for McAloon and other fishermen. He said the Friends of the Fox group is playing with fire by increasing boat traffic up the Fox River.

Friends of the Fox estimates up to 50,000 boats may use the river system once it is reopened for boating between Green Bay and Menasha. McAloon sees that as increasing the odds that a small, pregnant goby or some other invasive critter could slip through the inspection system. Moy points out that some boaters already trailer their boats from Green Bay to Lake Winnebago and are actually a greater risk for transporting a goby or spiny waterflea.

The stakes are high on all sides. Lake Winnebago is not only unique for it?s lack of lamprey, it?s also one of the last major refuges for the threatened lake sturgeon, which are particularly vulnerable to lamprey and other invasive species because they reproduce slowly.

The plan for the boatlift will be scrutinized in public meetings to be scheduled sometime this fall, and by the Wisconsin Department of Natural Resources and possibly the Sea Lamprey Control Program of the Great Lakes Fisheries Commission.

The Friends of the Fox group believes new boat traffic will boost the local economy, especially in Appleton and Neenah-Menasha. But some local fishing experts point out that Lake Winnebago already is home to a thriving sport-fishing industry. Besides lake sturgeon, Winnebago shelters a world-famous walleye population and other popular game fish.

"The last study I heard of said the fishing industry here is worth $400 million to the local economy," said Ron Bruch, a DNR expert on the lake sturgeon. "My take on it is, the sport fishermen and many people managing the ecosystem are opposed to it (the plan to restart river traffic), because even with a sophisticated decontamination system, even if there?s limited failure, the impact can be devastating."

Bill Bush, a boater and chairman of the Friends of the Fox committee on invasive species, said he is fully confident Moy?s plan for the boatlift will prevent unwanted passengers. Bush said the boatlift system would require two or three employees to run.

"We know people are interested, and we?re trying to make sure we appeal to all the communities up and down the river and groups like Walleyes for Tomorrow (one of the fishing groups expressing concern)," Bush said.