For a four-year-old, catching a fish, even one little fish, on a day out on the lake with Grandpa is the stuff of happy summer memories.
For the federal Department of Fisheries and Oceans (DFO) in Ottawa, the catch was grounds for serious alarm: An invader is in our midst.
The fish that little D.J. Williams caught was a round goby, native to the Black Sea but a nuisance species in the Great Lakes. Round gobies turned up in 1990 in Lake St. Clair - which straddles Ontario and Michigan east of Detroit - evidently after arriving in the ballast water of an ocean-going vessel. They've thrived in the waters around Chicago and Detroit for several years now.
But the young fisherman's catch near Picton, Ontario, represents the first spotting of the round goby in Lake Ontario.
DFO officials are worried that this aggressive little fish could put at risk a sport and commercial fishing industry in Lake Ontario worth nearly $100 million a year. A homely little thing, no more than 10 inches long, with its big head making it look like a tadpole, the goby isn't quite a piranha, but it isn't shy, either. It takes on other fish twice its size and could crowd out native species such as smallmouth bass, walleye, and lake trout.
Officials are scrambling to educate anglers and boaters about the dangers of inadvertently introducing the fish to new bodies of water, perhaps via a bait pail or a boat's intake pipe.
It's been about 10 years since the concept of "invasive species" burst into public consciousness, with the zebra mussel as their "poster child," as Michael Donahue, executive director of the Great Lakes Commission in Ann Arbor, Mich., puts it.
But hitherto, official efforts to deal with these "invaders" have focused on data gathering. "Right now," however, says Dr. Donahue, "we're moving full speed ahead" to get prevention and control measures in place.
The commission has released model legislation to the 10 American states and Canadian provinces that are its members.
Practical steps being taken range from the modest - public education - to the more heroic, such as the Army Corps of Engineers' plan to construct a kind of electric fence across the Chicago Sanitary and Ship Canal to keep nuisance species from jumping from the Great Lakes to the Mississippi River system.
The US and Canadian governments disagree on the effectiveness of one technique at the center of efforts to control nuisance species: ballast-water exchange.
A ship returning empty to home port typically fills up with harbor water as ballast, to hold it steady on the sea. Some seaports - on the Black Sea and the Baltic Sea, for instance - have water fresh enough to sustain freshwater creatures. So it's not hard for a freshwater "stowaway" to make it into a ballast tank and cross to the Great Lakes.
One way to control this is to require, as US law now does, ships headed for the Great Lakes to exchange ballast water on the high seas, to dump stowaways in the North Atlantic. But some Canadians point out that their vessels typically travel under rougher conditions, in more northerly latitudes. This makes ballast-water exchange difficult if not impossible. It may not even be the most important source of the problem, it is further argued.
The International Maritime Organization, a United Nations agency in London, is developing global regulations on management of ballast water, in the hopes of getting them adopted by 2002 or 2003.
The concern about the goby comes at a time when the numbers of the zebra mussel are in decline. The fingernail-size mollusk in a striped shell has wrought havoc in the Great Lakes region, clogging water intake pipes and interfering with fishnets. "But densities of zebra mussels are much lower than seven or eight years ago," says David Ankney, a zoologist at the University of Western Ontario in London, Ontario Natural predators have moved in, and the mussels have eaten lake bottoms clean.
A "successful" import, he says, typically attains a "really huge population and then falls back to a sustainable level" within the new ecosystem. "We can never predict with certainty what level an introduced species will settle into," says Dr. Ankney. "Most new species don't make it."
(c) Copyright 1999. The Christian Science Publishing Society