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Foreign species crowd out local fish
Quagga mussels and gobies are new threats to waterways
Muskegon-area fishermen captured this giant goby, which they dubbed "Goby Dick." Gobies eat the eggs of native fish and take over their spawning grounds and habitat.The region's most unwanted
Meet some of the species that are invading the Great Lakes.
At a fishing tournament Tom Matych held in June, 400 anglers caught 5,000 gobies and one perch in five hours. Experts blame the goby for the decline of native fish such as sculpin, darters and log perch.
The Great Lakes are in the throes of an environmental meltdown, with more than 180 foreign species of animal and plant life in its waters, scientists say.
The foreign species are gobbling up native fish, crowding out local fauna and wreaking havoc on the food chain.
These ecological changes are being spearheaded by some of the most destructive species ever to invade -- notably the zebra mussel and its cousin, the quagga mussel. Adding to the ecological damage is the explosion of the voracious round goby, which eats the eggs of native fish and takes over their spawning grounds and habitat.
"We are seeing changes in the Great Lakes that are more rapid and more destructive than any time in the history of the Great Lakes," said Andy Buchsbaum, director of the Great Lakes Office of the National Wildlife Federation based in Ann Arbor.
Most invasive species are believed to have entered through the ballast water of foreign ships. They spread via currents, the hulls of recreational boats and the bait buckets of anglers who accidentally transport them. Their proliferation has raised the ire of fishermen.
"I used to fish with a cane pole and catch 5-gallon buckets full of perch," said Tom Matych, 51, a shop worker from Twin Lake, near Muskegon, who remembers some great fishing trips in four decades of casting for perch, walleye and other sport fish on Muskegon Lake.
The last time Matych went out on the lake, all he caught were gobies. "We call it Gobyville now," Matych said. "It's tough to catch walleye and perch, but the gobies are everyplace you go."
To dramatize the explosion of gobies in the lake over the past five years, Matych held a fishing tournament in June. Four hundred anglers caught 5,000 gobies -- and one perch -- over five hours. The 460 pounds of gobies, worthless as food for humans, were discarded.
The goby, accidentally released into Lake St. Clair in the mid-1980's, has now proliferated across all the Great Lakes.
In addition to the goby and mussels, scientists are concerned about the spiny water flea and the fish hook flea, which feed on native zooplankton, decreasing food for young fish, said Tom Nalepa, a biologist with the Great Lakes Research Center in Ann Arbor.
"Larval fish don't feed on the spiny water flea and the fish hook fleas because of their long spines." Nalepa said.
Gobies blamed
Non-native species can be in the water for a long time before they're discovered, said Hugh MacIsaac, a Windsor University biology professor and leading expert on invasive species.
"One reason is they are introduced in small numbers and it takes time for the population to get large enough before they can be detected," he said. By that time, it's often too late to deal with the intruder.
Scientists theorize the fish hook flea, which measures an eighth of an inch, was introduced into the Great Lakes in the mid-1980s but wasn't discovered until 1998. It was found in Lake Ontario, but has now spread to all the Great Lakes.
MacIsaac, noting that there were only 139 nonindigenous species in 1993, said scientists were alerted to the fish hook flea by fishermen who complained it was fouling their fishing lines.
By contrast, it only took one or two years to discover the goby.
Dave Jude, the scientist who discovered it in the Great Lakes in 1990, said one study pegs the goby population in western Lake Erie alone at 9 billion.
"They are very abundant and dominate the bottom of harbors and lakes," said Jude, a researcher with the University of Michigan Center for Great Lakes and Aquatic Sciences in Ann Arbor. "In some cases, they make up 60 percent (of the marine life population), and the implications are staggering."
Gobies have been blamed for the steep decline of native fish such as sculpin, darters and log perch. They also eat the eggs of bass and sturgeon, the latter a species that has been fighting to survive.
Studies show one round goby can eat as many as 2,000 bass eggs in one feeding.
Native species can't find food
Besides gobies, zebra and quagga mussels have exploded by the billions across the Great Lakes, killing valuable food for fish, wiping out native marine life, disrupting the food chain and helping to create toxic algae conditions that have killed thousands of waterfowl. A "dead zone" in Lake Erie, where marine plants and animals cannot survive, has also been blamed on the two mussels.
The zebra mussel made its debut in Lake St. Clair in 1988. The quagga mussel came to the Great Lakes in the mid-1980s, but has exploded only recently in Lakes Michigan and Huron.
"In southern Lake Michigan, we had a 100-fold increase in quagga mussels. That is unprecedented," said Nalepa.
Both mussels are being blamed for the eradication of diporeia, a quarter-inch-long shrimplike creature that is a basic food source for fish.
"Between 1992 and 2000, there was a 66 percent decline in diporeia in Lake Michigan," said Nalepa, estimating that 1.7 trillion diporeia were wiped out in the lake.
Nalepa said studies show a sizable decline in Lake Huron also.
The loss of diporeia has been blamed for the steep decline in perch in Lake Michigan and emaciated whitefish in Lakes Huron and Michigan. The loss is also partly to blame for the decline in alewives in Lake Huron. The decline in alewives in turn has been largely blamed for skinnier salmon, said Dave Borgeson, a supervisor in the fisheries division of the Michigan Department of Natural Resources.
"In a lot of areas in Lake Huron, diporeia have gone from 1,000 per square meter down to zero," he said.
Of the two mussels, the quagga mussel worries scientists more because it can thrive in deeper, colder waters than the zebra mussel. That means trouble for the opossum shrimp, another native crustacean that is the key food source for fish in deeper waters.
The mussels cause harm in other ways, too. They are loaded with toxins such as cancer-causing PCBs absorbed from the water in the Great Lakes. The carcinogen is passed on to fish that feed on them, particularly gobies, which gorge themselves on the young mussels. The danger to humans is that bass, perch and walleye -- popular with diners -- eat gobies and also absorb the PCBs.
"We have found high concentrations of PCBs in gobies in the St. Clair River, Raisin River and Calumet Harbor," Jude said.
Mussels are a costly bother
The zebra mussel, however, was the first to make a significant impact. Within years of its arrival, the thumbnail-size striped mollusks had spread into Lake Erie and started clogging intake pipes at power plants and the irrigation systems of golf courses that drew water from waterways infested with the clams.
DTE Energy spends $500,000 a year to remove zebra and quagga mussels from water intake pipes at its plants in Monroe, Belle River, St. Clair, River Rouge and the Fermi nuclear power plant near Monroe, said Bill Kovolak, a DTE biologist. Zebra and quagga mussels were recently discovered at the Trenton Channel Power Plant.
But the number of mussels removed has decreased dramatically since 1989, the first year the mussels clogged intake pipes in Monroe. "The numbers are pretty low -- 10,000 per square meter, compared to 800,000 per square meter in 1989 -- the highest ever recorded in the Great Lakes, and higher than what is seen in Europe," Kovolak said.
The mussels are not spawning as much because they have depleted the supply of algae, he said. Each female zebra and quagga mussel can lay between 40,000 and 1 million eggs a year, depending on the size of the mussel.
Bob Frick, who lives on Crescent Lake in Oakland County, has a different problem with zebra mussels.
"I scrape pails of them off the bottom of my pontoon boat," said Frick, a retired engineer with the Fisher Body division of General Motors Corp. "And you don't want to step on them when you walk in the water. They will cut your feet."
Beyond being a costly nuisance, zebra mussels have eradicated the native clam population in Lake St. Clair. They also have caused the disappearance of zooplankton by filtering out algae.
One beneficial change: The disappearance of algae led to a massive growth of aquatic plants in the shallow lake because sunlight was able to penetrate to the bottom. The heavy weed growth is good for bass, pike, walleye, perch and other fish, said Mike Thomas, a biologist with the Michigan Department of Natural Resources research station along Lake St. Clair.
"Heavy plant growth provides cover for young bass and other fish, and provides spawning habitat for fish like yellow perch, which actually lay their eggs on the plants," Thomas said.
Science offers some hope
Scientists are searching for ways to eradicate non-native species.
A faint hope to control zebra mussels might be found in a bacterium called pseudomona fluorescens that occurs naturally in some waterways. Tests show it is lethal to zebra mussels, but does not appear to affect other aquatic species, said Dan Molloy, director of the New York State Museum Field Research Laboratory in Cambridge, N.Y.
"There is something toxic about this strain of bacteria ... it destroys the digestive gland in zebra mussels," said Molloy, who found the bacterium in the mid-1990s after examining 700 types of bacteria.
Molloy said he is trying to develop a method to economically mass-produce pseudomonas fluorescens to kill zebra mussels in power plants. He does not think the bacteria can be used in large bodies of water, only to treat small sections of lakes or canals.
Meanwhile, in the laboratories at the University of Windsor, Lynda Corkum, an aquatic biologist, has been working for the past three years on developing a pheromone that will lure female gobies into traps. Male gobies produce chemicals called pheromones to sexually attract females.
The pheromones, however, could only be used in isolated areas where native fish, such as bass or sturgeon, spawn.
"But there are so many gobies we could never capture them all; it's just not possible," Corkum said.
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