Odds Are Vermont Will See The Invasive Spiny Water Flea

Jul 7, 2014

The spiny water flea is a creature as disgusting as its name implies. It resembles a bristly glob of jelly with little black spots all over it. But its looks are not the real problem.

This tiny invasive pest can disrupt the food chain in a water body, hook itself to fishing lines to annoy anglers, and it can be a big problem for fish.

Oh, and by the way, it’s been found in Lake George and environmental officials are bracing for it to find its way into Lake Champlain sometime soon.

The spiny water flea is a predatory zooplankton, and its larger size means it’s visible to the naked eye. They are thought to come from eastern Europe or western Asia through the Great Lakes, where they were probably discharged in shipping ballast. They were first detected there in the 1980s.

"Fish will feed on these in the absence of anything else, or in the absence of enough other things, and they'll end up feeling full, full stomachs, but they'll have very little nutritional value in there." - Fred Dunlap, New York Department of Environmental Conservation

Fred Dunlap, Lake Champlain coordinator for the New York Department of Environmental Conservation, said it’s a great unknown whether they’ll make it into the big lake.

“It seems probable at this point with them being in Lake George and also in the canal system. The odds are stacked against us at the moment, but our monitoring has not found them yet, so we can remain somewhat optimistic,” he said.

The zooplanktons that spiny water fleas feed on are also the preferred food for forage fish and juvenile fish, so it ends up being a competitor for the zooplankton.

“If you have a population of spiny water fleas and they end up putting a dent in the preferred zooplankton out there, it can affect growth rates of these small fish that are looking to feed on the same thing,” Dunlap said.

Still, there have been no measured impacts of the spiny water flea in Lake George. They were first detected there in 2012, and scientists suspect they were in the lake for a while before detection. But the fleas react differently in each water body, and Dunlap said ecosystems seem to find a way to balance themselves out.

The fish will eat the spiny water flea, Dunlap said, but their long tail spines make them not easily digestible and they don’t have the same nutritional value as the preferred zooplankton.

“Fish will feed on these in the absence of anything else, or in the absence of enough other things, and they’ll end up feeling full, full stomachs, but they’ll have very little nutritional value in there,” Dunlap explained. “And that’s what affects their growth rate that way.”

There is no practical way to keep them out of Lake Champlain, as their tiny size makes them hard to manage. Dunlap said they’ll continue moving northward and there’s no way to extract them from the water column.

There are 15 lake monitoring stations in the lake, the canals and on the La Chute River. Scientists do net pulls every two weeks to look for them.

“They might be detected sooner by anglers who are trolling long fishing lines out behind them, as the spiny water flea quite often attaches to them,” he said. “So we may hear from fisherman that they’re in the lake before we’re able to find them in our sampling program.”