Alien Invaders Coming To a Lake Near You-

Susan Peterson Gateley 1100 words

12025 Delling Rd Wolcott NY 14590 susan@silverwaters.com

Big head carp, round gobies, fish hook water fleas- they're new, they have potential to devastate native animal life, and they've all reached Lake Ontario's shores. Last summer a number of alien invader fish stories made headlines. The media loved voracious three foot snakeheads that could travel overland, found in a Maryland pond last spring (and reportedly taken at least once from the Cayahoga River, a tributary of Lake Erie). More recently an even more far fetched series of invader fish tales made the news in Great Lakes cities- flying Asian carp some of which grow to over a hundred pounds. "These fish consume vast amounts of food. They are highly prolific and can quickly grow to a size at which they have no natural predators" says Dennis Shornak of the International Joint Commission.

Exotic "weed" species like the carp are not new in Lake Ontario. One of the first invaders, the sea lamprey virtually wiped out a multi-million dollar commercial fishery for lake trout . And another exotic, the herring-like alewife, a native of saltwater, is now the main prey fish feeding the hungry salmon and trout that support a vast sport fishing industry.

But since the St. Lawrence Seaway opened, the pace of alien invasions has picked up sharply. And as global trade increases and faster ships cross the Atlantic in less time, more and more alien critters hitch rides inside ship ballast tanks and survive the crossing. At least 145 different plants and animals have established populations in the Great Lakes. The zebra mussel, originally from the Caspian Sea area, is estimated to have cost Great Lakes municipalities, factory and power plant operators more than 2.5 billion in water intake clean up costs. And the International Joint Commission in a letter sent to Secretary of State Colin Powell last July warned "Scientific consensus indicates that the introduction of Asian carp may result in economic and ecological damages to the Great Lakes ecosystem that far exceed those brought about by the sea lamprey and zebra mussel."

Some of the recent invaders like the little fish hook water flea, first seen in Lake Ontario in July 1998, seem inconsequential. About the only complaint so far that this little half inch long shrimp like creature has prompted is of fouled fish lines. But tiny animals and plants that make up the floating plankton of Lake Ontario can have very big effects on the lake's food chain. The fish hook water flea preys on smaller water fleas that are important as the first food of just hatched fish. Baby fish an inch long can't tackle a fish hook water flea for dinner- its too big. And by eating the same things the little fish eat, the new water flea competes directly with baby fish. How important a competitor is it? No one really knows yet, says Chuck O Neill of Sea Grant's Brockport office, but surveys have found up to 600 water fleas in a cubic meter of Lake Ontario water when their population peaks in late summer- a very high number of predators.

O'Neill explains that preliminary research does show that on Lake Ontario "when the fish hook water flea population goes up, populations of smaller water fleas decline." On the positive side, some studies suggests adult alewife happily eat fish hook water fleas. Will it help or hurt the Lake Ontario fishery? We don't know yet.

There's little doubt in the minds of most fishery biologists about the potential impact of another new invader, the bighead carp. It'll be huge. Bighead carp are one of several species of Asian carp imported into the southern US in the 1970s to clean up commercial fish farm ponds of unwanted algae, snails and vegetation. Big Heads can grow to 100 pounds in a few year's time. "Kevin Irons of the Illinois River Biological station explains "All fish during their life depend on plankton to some degree. After hatching, fish depend on plankton for fast growth. As they grow, they then change their habits…(but) some use plankton throughout their lives. So a strong silver/bighead carp population could influence the whole lake fish community." And they grow so fast that they soon are too big for anything to eat them. One species the silver carp, can grow to 12 pounds in just one year. Bighead carp are native to northern Asian they have worked their way up the Mississippi to within a few miles of Lake Michigan. They seem likely to thrive in the Great Lakes once they get there.

These fast growing fast reproducing carp simply over ran native fishes in the Mississippi. In some stretches of the river 90 % of the total weight of fish collected in surveys are now carp. Dennis Shornak, warns "We could honestly end up in a situation where the Great Lakes are nothing more than a carp pond." A sport fishery that on Lake Ontario alone contributes millions of dollars a year to the local economy could well collapse if bass and brown trout and chinook salmon find themselves shouldered aside from the dinner table by hundred pound carp.

Right now says Chuck O'Neill of New York State Sea Grant, there is a lot of educational effort directed towards the carp problem. "If you do catch one, kill it. Don't let it go again." For more information on what the various Asian carp species look like visit the International Joint Commission's website at www.irjc.org or contact Sea Grant for more information. One way these fish are apparently being spread is through dumping of live bait. So if you are an angler, don't release any unused minnows into the bay as there could be a baby carp mixed in with them.

The Asian carp won't mix well with jet skies either. When startled by a noisy fast moving boat they jump. Fish weighing up to 15 pounds leap five or six feet out of the water. Jumping fish have reportedly smacked boat operators in the face causing injury. Irons says that while he thinks some of these flying carp stories are fish tales "I have heard stories of people being knocked off jet ski's, being knocked out, and getting broken teeth broken collar bones." He adds "I have witnessed people using folding chairs to deflect an incoming carp." Jerry Rasmussen of the US Fish and Wildlife Service who works on the Mississippi River was quoted in a recent Detroit Free Press article that " Some of our staff have been hit multiple times by big carp that landed in research boats."

Unfortunately the big head and silver carp while reputedly being tasty to eat, are difficult to catch. Irons told me with his tongue in cheek that the silver carp might hit a trolled spoon "However, it is much more efficient to boat around and pick them off your boat floor". The good news is that, as of this writing, no bigheads or other Asian carp species have yet been sighted in Lake Ontario. But several large ones have appeared in Lake Erie and two were found recently in a fountain in Toronto.

So if you want to sign up this summer for a ride with Silver Waters on the lake, maybe we can sight a flying fish!