Air Date: Week of December 27, 1996
A newly introduced fish is rapidly reproducing in the Great Lakes. The Goby fish, originally from Russia, is thriving in all five of the Lakes. Bob Carty of the Canadian Broadcasting Corporation reports on the proliferation of this non-native species and its impact on the food chain.
CURWOOD: It's Living on Earth. I'm Steve Curwood. For almost a decade, people who live around the Great Lakes have been complaining about a foreigner, a non-native species of shellfish called the zebra mussel. The zebra mussel has multiplied so rapidly that it has changed the region's ecology, and clogged the intake pipes of water systems and industrial plants all around the Great Lakes. Now, another non-native species has been found in the lakes, a fish that eats zebra mussels. Could this be an ironic writing of an ecological imbalance? Well, not really. Bob Carty explains.
(A foghorn sounds)
CARTY: On the Detroit River just a couple of miles above the canyon of Detroit's skyscrapers, Patricia and Gord cast their lines into the muddy water a couple of times a week. Pat and Gord fish for fun; that's something there seems to be less of every day. Fishermen around here have to wear heavy boots so their feet aren't cut up by the shells of millions of zebra mussels that carpet the shoreline. And if zebra mussels weren't enough, anglers like Pat and Gord now have to put up with annoying tugs on their bait.
CARTY: What are you fishing for?
PAT: Perch. Not catchin' any. (Laughs)
CARTY: What do you usually catch?
PAT: That's new in the water. It's a small little fish that looks like it has a suction cup on its stomach and it comes from Europe.
GORD: They come out of the ships, ballast water I guess, and they dump it in the lake and that's how they got started I guess.
PAT: My brother in law thinks they're going to take over the water, because they multiply real fast.
CARTY: Real fast indeed. The goby fish was first discovered near here just 5 years ago. By this summer, the goby had spread to all 5 Great Lakes, from Lake Superior to Lake Ontario.
JUDE: When you look at other alien species that have come into the Great Lakes, like the alewife and the sea lamprey, it took them up to 20 years sometimes to make it all the way through all 5 of the Great Lakes. This species is doing it different, and we've really not had that kind of a transfer of alien species before.
CARTY: David Jude is a researcher at the University of Michigan's Center for the Great Lakes and Aquatic Sciences. He is also the owner of a Michigan license plate that reads GOBY-1. That's because in 1990, David Jude was the first person who found a goby a long, long way from home.
JUDE: Gobys are members of the second largest fish family in the world, and they include a lot of cave fishes. In other words, they can feed at night in complete darkness, and that may have also been one of the traits that allowed them to get over here in the first place because they were in the ballast water of a ship in the dark.
CARTY: Where are they from?
JUDE: They're from the Black and Caspian Seas in former Russia.
CORKUM: This is our lab freezer, and in here I have everything from frozen gobys to frozen adult insects.
CARTY: At the University of Windsor, on the Canadian side of the Detroit River, biologist Linda Corkum shows off the contents of some plastic bags in her freezer.
(Plastic bags crinkle)
CORKUM: And here's a goby. When you open the gut of a round goby you find all sorts of prey items, and in this one you can see that there are actually zebra mussels intact in the gut of the fish. It's quite amazing.
CARTY: And for a time, at least, quite promising. Here is a fish that loved to eat the little emigre from Russia. It devoured zebra mussels by the dozen. Now this was good news around the Great Lakes. After all, zebra mussels were becoming so numerous that they were sinking navigational buoys by their combined weight. Throughout the Great Lakes it has cost an estimated three quarters of a billion dollars up to now to protect water intakes from zebra mussels. So the goby was the great brown hope. But a false hope it proved. Aquatic scientist David Jude.
JUDE: There's lots more zebra mussels than there ever will be gobys. They do eat a lot of zebra mussels, but I don't think they're going to exert any big control on zebra mussels; they're certainly no silver bullet for controlling zebra mussels. But they're another factor that will help control the zebra mussel population.
CARTY: The goby's appetite for zebra mussels may in fact be a serious problem. It's a matter of the food chain according to Dr. Linda Corkum. The problem is that after eating zebra mussels, the gobys are eaten by bigger fish.
CORKUM: Zebra mussels are associated with the bottom, and accumulate contaminants: PCBs, industrial byproducts, pesticides, a whole suite of organochlorines. And gobys will be able to transfer these contaminants to predatory fish. Such as the sport fish such as small mouth bass or various species of trout.
CARTY: If this food chain concentration of toxin occurs as scientists predict, anglers might have to stop eating some of their favorite sport fish. Part of the commercial fishery might even be threatened. And that's not all. Gobys can out-compete other fish for food. They're more aggressive. They can feed in dark waters. They spawn 6 times a year. And because they can eat zebra mussels, gobys have an unlimited food supply unavailable to other fish. David Jude has already seen the impact, particularly on a once abundant native species.
JUDE: A species of benthic, which is a bottom dwelling fish, called the model sculpin, has been almost totally eliminated or displaced by the round goby. To find this is really an astounding discovery; I've heard these reports from scuba divers, and it's also been reported from the Grand Calumet River. The other interesting part of that is that the Grand Calumet River connects with the Mississippi River at Chicago, in that area. So now they have got an access into the Mississippi River, too.
CARTY: The goby is just the latest example of how disruptive non-native species can be. Earlier, the lamprey eel nearly destroyed lake trout. More recently the zebra mussel turned Lake Erie from murky to clear by eating most of the lake's algae. And now the goby is changing the balance of biodiversity. On the bright side, in the future there may be fewer cases of non-native species hitching a ride into North America. Both the US and Canada have taken measures to get ships to exchange their bilge waters at sea before entering inland waterways. But David Jude laments that short of serving up gobys on our dinner tables, like they do in Russia, there's really nothing to be done about the non-native species already here.
JUDE: Exotic species are forever. They get into these lakes and they take over and they're here for the duration, and we're just going to have to live with them.
CARTY: For Living on Earth, I'm Bob Carty in Detroit.
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