The corner tank in the corridor behind the Illinois Lakes and Rivers gallery at the Shedd Aquarium isn't pretty, but to the 260 sturgeon inside it's home. When placed in the concrete tub 14 months ago, the fish were mere fingerlings, about four inches long; now they're two feet long or longer, with dorsal spikes you could cut your finger on and powerful mouths that can suck a round goby out from under a rock--which is just the job that Roger Klocek, the aquarium's senior conservation biologist, raised them to do. Lucky for the gobies of Lake Michigan, however, the laboratory-raised sturgeon will not be reporting for duty as planned.
Round gobies were introduced into the Great Lakes in ballast water discharged by commercial vessels from the Black and Caspian seas. First spotted in the Saint Clair River in 1990, the small fish (the largest grow to ten inches) are now found in every one of the Great Lakes. They're spreading into rivers and canals, and biologists fear they'll soon reach the Mississippi. Why such concern over a tiny exotic fish? Adaptable, hardy, aggressive, able to swim and feed in total darkness and to thrive in deeply polluted waters, round gobies can outswim, outfight, outeat, and outspawn every other bottom feeder in North America. In Lake Michigan they've driven native species like the mottled sculpin and logperch from their ecological niches, and they're decimating the egg stocks laid by lake trout, bass, and other prized sport fish. In a 1995 paper entitled "Round Gobies Invade North America," biologists J.E. Marsden and David J. Jude reported that "densities of gobies in rocky areas at Calumet Harbor already exceed 20 per square meter--equivalent to 20 fish in a space the size of a bathtub."
The only positive thing to be said for the gobies is that they eat zebra mussels, another exotic species introduced into the lake via the same route in the late 80s. A single goby can reportedly eat 78 zebra mussels a day. Unfortunately, that isn't enough to cancel out the damage either species is doing. Like gobies, zebra mussels breed like roaches and eat like Pac Man--specifically, they strain the water clean of the phytoplankton that fish larvae need to grow into fingerlings. The Shedd has gobies on exhibit in the exotic tank in the Illinois Lakes and Rivers gallery, but no zebra mussels. "We can't keep them alive," Klocek says. "They eat so much, you can't keep enough food in the water."
Klocek got the idea of enlisting sturgeon in the fight against gobies and zebra mussels from University of Wisconsin-Milwaukee scientist Fred Binkowski. A pioneer in the technique of hatching and raising sturgeon, Binkowski knew that sturgeon in the Caspian Sea fed on both pests and had seen data suggesting that American sturgeon were partial to them too. Moreover, as Binkowski told Klocek at the fourth International Symposium on Sturgeon in Oshkosh in 2001, he'd always been impressed by the ferocity of the sturgeon in his lab. Although generally slow and docile, the fish became frenzied when Binkowski threw alewives or gizzard shad into their tank. "He said they looked like little sharks tearing into those fish," Klocek says. The solution to the invasive species problem, concluded Binkowski, was to restock the lake with sturgeon, which would have the added benefit of restoring a native species to its former prominence.
Extrapolating from the size of catches recorded in the 19th century, scientists estimate that there were once 11 million sturgeon in Lake Michigan, but the population abruptly collapsed in the early 1870s due to overfishing and has yet to recover. Today there are fewer than 1,000 sturgeon in the lake.
But Binkowski's proposal for restocking the lake would work only if the sturgeon were raised to maturity before being released into the wild. Stocking the lake with sturgeon larvae would be tantamount to serving a buffet to the gobies, while fingerlings would be snapped up by bass. "But once the sturgeon get up to a foot long, nobody's gonna mess with them," says Klocek. "We said, you know, we could do this. The technology is there."
In April 2002 Klocek acquired a starter kit of sturgeon embryos from the Wolf River-Lake Winnebago area in Wisconsin. To create these embryos, Wisconsin fisheries biologists netted individual fish and manually extracted roe from females and milt from the males. "They're careful to take only part of the roe and the milt," says Klocek, "and the whole process takes place just a few feet away from the water. It's very fast, and then the fish slide back into the water along a smooth, wet canvas chute, and they go on to complete their spawning." The roe and the milt were combined on the spot, placed in special incubating containers called McDonald jars, and shipped to Binkowski's Wisconsin laboratory. "When the jars arrived at the lab we put them into special tanks," says Klocek. "There's a current of oxygenated water that moves through the jars, and as the eggs hatch, the larvae, which are about three-quarters of an inch long, are carried by the current over the lip of the jar and into the open water of the tank, and that's how they were born." By July, when they were shipped to the Shedd, the hatchlings had grown into four-inch fingerlings.
If things had gone according to plan, Klocek's sturgeon would have been released into the lake a couple of weeks ago. But an unforeseen obstacle arose at a conference of the Lake Sturgeon Task Group of the Lake Michigan Committee, a meeting of scientists, state officials, and representatives of the Chippewa Ottawa Resource Authority (a native Indian fishing organization) that took place in Menominee, Wisconsin, early last September. Geneticists at the conference successfully opposed the plan on the grounds that it might genetically homogenize the remaining sturgeon populations in the lake. "The latest information shows that the Michigan populations and Wisconsin populations are genetically different," explains Klocek. "Biologically, you should try to preserve the difference wherever you can, if it's feasible."
The threat of homogenization stems from the fact that Klocek's sturgeon were artificially hatched. Wild sturgeon imprint on the places they were spawned and return there to reproduce--a trait that discourages interbreeding among different populations. "The fish that spawn at Green Bay are always going to return there because the larvae imprint on that water's taste. Here, our fish have imprinted on the taste of water from the Jardine Water Filtration Plant, or maybe the water in Fred Binkowski's lab. Either way, they're going to be homeless when we put them into the wild."
If they're unable to find water that tastes like home, spawning sturgeon will settle for the best conditions they can find. But all sturgeon migrate around the lake in a counterclockwise pattern, from northwest to northeast, which means that Klocek's sturgeon would eventually end up in Michigan waters. "Our fish are not going to return to Wisconsin streams to spawn," he says. "They're going to wander the lake. And when they get there they're gonna say, hey, the water's pretty good, and there are other fish spawning here, so let's spawn! They'll probably interbreed with the Michigan fish, and you're going to lose that genetic strain, which could be a bad thing 200 years from now when the populations are built back up to millions of sturgeon. We'll have diluted the genetic diversity. This sounds very German, doesn't it? I'm scaring myself."
Initially angry at the cancellation of the program, Klocek has come around to agreeing with its critics. "I want to blame somebody for this, I really do," he says, "but I can't. I was really peeved at first. It was like, you guys are putting up these roadblocks. But thinking about it, it's a good roadblock to put up. If somebody came up and said, 'You know, it's your call, do what you want, we won't stand in your way,' I'd say we shouldn't put these fish in the lake."
For now the sturgeon are stuck--all grown up with no place to go. Klocek explored the possibility of sending them back to Wisconsin, only to discover that this would be illegal. "There's a law on the books in Wisconsin that says fish going into public waters cannot be raised outside of the state," he says. "Why, I don't know, but that was it."
Ray Owczarzak, an aquarist who helps look after the sturgeon, says they're not expensive to keep. They share five pounds of chopped smelt, clam, mussel, and krill a day, delivered in a frozen block that's slapped up against the side of the tank until it sticks and then slides slowly to the bottom. "Same theory like a tongue on a light pole," Owczarzak says. "The difference in temperature makes the food stick, and that way they're all able to come right up to the food." Owczarzak says that little is known about the sturgeon's growth patterns, but he reckons the fish could survive another year together in their 900-square-foot tank.
Klocek think that's plenty of time to find a home for them. Sturgeon restocking programs in both Tennessee and Georgia have expressed interest, though neither has been able to come up with the money to rent the water truck and hire the crew needed to move the fish. "Somebody's going to take them," Klocek says. "These fish that we have are a year and a half old and big enough to radio-tag. Our guys are extremely desirable, it's just that nobody's got the funding right now."
For the time being, Klocek's guys aren't going anywhere. The same goes for the zebra mussels and round gobies in the lake.
Art accompanying story in printed newspaper (not available in this archive): photos/Lloyd DeGrane.