UNIVERSITY PARK, Pa. -- The first time the funny-looking little fish with the raised, frog-like eyes and thick lips was seen in the Pennsylvania waters of Lake Erie was in 1996, when a few of the mottled, flat-faced creatures from Eurasia turned up in Pennsylvania Fish and Boat Commission sampling nets.

Back then, scientists weren't even sure what they were. Today, they know -- gobies are the mother of all invasive fish species, and there are now by far more pounds of them in the lake than any other fish.

Their exploding population is having a huge impact, warns Renea Ruffing, a researcher in Penn State's College of Agricultural Sciences, who has been studying the exotic species in Lake Erie for three years under the guidance of renowned ichthyologist Jay Stauffer. Already many sculpins and darters have disappeared from Lake Erie, either eaten or out-competed for food by gobies. Ruffing fears gobies threaten sensitive aquatic life not just in the Great Lakes, but across the state and perhaps the country.

The first time Ruffing, a Huntingdon County resident pursuing a doctoral degree in ecology, saw gobies, she was scuba diving a few years ago in Lake Erie. "We swam over a rocky area, and it was unbelievable," she recalls. "It seemed like there were millions of them, covering the bottom as far as you could see, all of them looking up at us with those bulging, unblinking eyes. I don�t think most people fully realize the scope of the goby invasion -- it's enormous!"

Gobies, which average only 18 cm (about 7 inches) long when fully grown -- a really big one might measure 28 cm (about 11 inches) -- have strong jaws, big heads and wide mouths relative to their small bodies. They swam into perfect habitat when the first ones were inadvertently released into the Great Lakes system from the ballast of some ocean-going vessel a decade or so ago.

The Great Lakes previously had been invaded by zebra and quagga mussels, and the shallowest Great Lake, Erie, offers fertile habitat in abundance for both Asian invaders. The shellfish populations have exploded. As it turns out, mussels are gobies' favorite food, so their numbers also have reached staggering proportions in Lake Erie.

"Gobies are prodigious breeders," Ruffing points out. "They are nest guarders that chase predators away from their eggs, so that gives their fry a much better chance of surviving. And they spawn most of the year."

In Eurasia, people eat gobies, says Ruffing. They trawl for them and there is a commercial fishery for gobies. "But the problem with gobies in the Great Lakes is that they eat both quagga and zebra mussels," she says. "And those mussels have been found to be high in heavy metals, presumably because they have filtered toxins from past and present pollution out of the lake. It wouldn't be healthy to eat them here. Still, with so many gobies, from the studies I have seen, they haven't put a dent in the mussel populations."

In Eurasian waters, gobies were originally a brackish water fish, notes Ruffing, who says they have adapted "amazingly well" to fresh water. But it is those saltwater roots that have Ruffing and other scientists so worried about the havoc gobies could wreak in the United States.

"We are worried about them getting into the Susquehanna River and the Chesapeake Bay," she says. "Can you imagine what they might do to the bay? They could wipe out the shellfish in the Chesapeake. Most of our native mussel species already are either endangered or threatened. Researchers now are studying the saline tolerance of the gobies to see whether they would readily adapt to the waters of the Chesapeake. We hope not."

Ironically, an infestation of gobies in brackish waters here might be beneficial to some species. "It might help the sturgeon population," she says, "because in the Caspian Sea, gobies are the main food fish for sturgeon."

Some gamefish species feed on gobies. For instance, both smallmouth and largemouth bass in Lake Erie target them, and bass numbers seem to be rising. The fact that gobies are such good bait for bass in Lake Erie has Ruffing and others worried that it will contribute to their spread into other waters.

"Gobies are deadly bait for bass in Erie," she observes. "How long will it be until some angler takes a bucket of gobies bass fishing in French Creek or the Susquehanna River, and then dumps them in after he's done? It may already have happened."

Most discussions of gobies in Lake Erie have focused on the round goby, but Ruffing believes other species may be present in the Great Lakes. "There are nine closely related species of gobies in the Caspian Sea," she explains. "I find it highly unlikely that there is just one species in Lake Erie. Gobies in the Caspian Sea can hybridize, so we might have hybrid gobies. Some of them look different."

The goby population explosion has occurred at the same time as the apparent collapse of Lake Erie's highly valued walleye population and scientists are wondering if the two events are connected. "We have absolutely no proof," Ruffing says. "But imagine if walleyes are broadcasting their eggs in places where there are millions of gobies on the bottom gobbling them up? That might explain a lot."

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EDITORS: Contact Renea Ruffing at 814-667-2276 or e-mail rar155@psu.edu.

Contact: Jeff Mulhollem jjm29@psu.edu 814-863-2719 814-863-9877 fax #291