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The Environment Report
Thu July 10, 2014
Bass getting fat on invasive fish
The bass are getting fat.
Lake Michigan was recently recognized as one of the best places in America to fish for bass. The booming fishery is one sign of what might be a major shift of the lake’s food web.
But that change is being driven by an increase in goby, an invasive species. And it could spell trouble for salmon— the most popular sport fish in Lake Michigan.
A change in business plans
Chris Noffsinger has an unusual specialty as a fishing guide. He shows you where to catch bass. Most charter fishing up north is for salmon, which are often three or four times times the size of the biggest bass. Noffsinger worked on salmon boats as a teenager, but when he started his own business he decided to switch.
"Bass is all catch and release and I really enjoy that factor, salmon and lake trout fishing is all catch, clean, kill. I don’t have a problem with that, I was just ready for a change. I really enjoy the bass side of things," Noffinger says.
Noffsinger is busy these days. He’s been on the water almost every day since the end of April.
He often fishes in Grand Traverse Bay, which Bassmaster magazine recently named the ninth best place to fish for bass in the United States.
Noffsinger says the fishing has always been good here, it's just been getting more attention in recent years. But he says the fish are changing.
"They’re getting fat... we caught one the other day that was 21 inches long and had a 20 inch girth. So it was as fat as it was long."
Researchers say the bass in northern Lake Michigan are some of the fattest in the country. It’s no mystery why. Bass are eating round gobies, a little baitfish native to the Caspian and Black Seas.
Gobies first showed up here about 20 years ago, and now they’re everywhere.
Dave Clapp manages the state’s research station in Charlevoix. He says gobies are thick in the rocky areas where smallmouth bass tend to hang out.
"You can see 100 gobies in a square meter of the bottom of the lake so they’re real plentiful when you get in the habitat that’s appropriate for them," says Clapp.
Goby numbers hard to determine
The most recent estimate from the U.S. Geological Survey suggests gobies now make up about one fourth of all the food available to big predator fish in Lake Michigan.
But John Janssen, a biologist at the University of Wisconsin-Milwaukee, thinks that estimate is low. He says the surveys are done with trawl nets and in sandy areas of the lake so surveyors see only a small part of the goby population.
"It’s trivial compared to what’s on the rocky habitat, that's just harder to sample; you have to send scuba divers down or submersibles or something like that."
Janssen says the expanding goby population in Lake Michigan is a coastal revolution.
The implications could be drastic.
The upsides and downsides
Gobies are known to carry a type of botulism that has killed thousands of shorebirds along the lake. But gobies also feed on another invasive species, the zebra mussel, which is responsible for dwindling fish and clam numbers in Lake Michigan. A single goby can consume about 100 zebra mussels a day. And a goby boom could also spell trouble for the most popular sport fish in the lake — salmon.
The food supply for salmon in Lake Michigan has been dwindling for years. And Janssen says they don’t seem to eat gobies.
"The salmon pretty much evolved as a herring predator, the way its mouth is shaped is adapted for feeding in the water column. They apparently don’t even look down in the rocks for gobies."
If salmon can’t thrive in Lake Michigan, it would be an economic blow to cities like Frankfort and Ludington, because those ports have many charter fishing businesses.
But Janssen sees some upsides to the goby, since native fish like bass and lake trout are eating them. He says if managers are looking to stock a monster sport fish like salmon, they could consider brown trout. That fish seems to like gobies, too.
Two of the three largest brown trout ever caught in the world, on record, came out of Lake Michigan in the past five years.
The Environment Report