The secret lives of fishes
Written by The Columbus Dispatch   
Tuesday, 11 July 2006 16:11

Todd Hayden put on a faded T-shirt and picked up the tools of his trade — a hacksaw, a linoleum knife and a thawed white bass. The researcher, who sat at a lab table surrounded by dozens of jars containing hundreds of preserved walleye and yellow perch, pinned the bass to a tray and began to cut away its head.

Inside the fish, between its brain and swim bladder, Hayden said, is a secret — one that could change the face of commercial fishing and how officials protect fishes throughout the Great Lakes.

After he created an opening, Hayden picked up forceps and carefully extracted two otoliths, or "ear stones."

Each calcium carbonate flake, smaller than a half inch, contains the fish’s life history, including where it spawned and its migration patterns through Lake Erie. Bowling Green State University researchers say this information could change the lake’s annual billion-dollar fishing industry. Commercial fishermen, scientists and conservationists are enthusiastic. "We would have one thing that would have a million answers," said Tom Mayher, a Lake Erie commercial fisherman for 55 years. Think of it as a type of MapQuest for the lake, guiding fishermen and researchers to areas where different fishes congregate.

That’s the kind of information that also could help the state protect species from extinction, said Mayher, the Ohio director for the Great Lakes Sport Fishing Council and chairman of the North Coast Sport Fishing Council.

The 76-year-old Cleveland angler said he and others no longer can fish for blue pike, a walleye subspecies that was overfished and driven to extinction in the 1960s.

Mayher said he hopes information derived from the otolith will help keep other fishes, such as the smallmouth bass, from a similar fate.

Otoliths — there are three pairs in every fish — are similar to tree trunks. As a fish grows, so does its ear stone, giving those who read it an accurate age.

Rings form in the otolith during winter, when fishes consume less and aren’t growing, said Jeff Miner, an associate professor of biological sciences at Bowling Green.

But there’s more to the ear stone.

It also records between the rings natural trace elements — strontium, barium, manganese and magnesium — from lake waters. Researchers can pair the chemical composition in the otolith to different areas in Lake Erie, said Miner, a fish ecologist.

The Bowling Green research team, which focuses on the Sandusky River as well, matches the strontium levels in the water to the otoliths. Researchers say they can tell where the fishes spawned — information that might help them uncover their migratory routes.

For example, the Sandusky has a higher concentration of strontium, which serves as a tag after the fish migrate into Lake Erie.

In addition to fish sampling, Miner’s research team collects water from the Maumee and Sandusky rivers, and where the Detroit River meets Lake Erie.

This is the kind of information that can help the state manage the lake, said Roger Knight, an administrator with the Ohio Department of Natural Resources.

And it could help officials better understand invasive species and help prevent overfishing.

"It will improve our ability to estimate how many fishes are in the lake, and how many can be removed by fishers," said Knight, adding that the otolith is a more efficient marker than traditional fish tags.

But before the lab work begins, researchers must first catch their subjects. Hayden guides a 1973 aluminum boat around Put-in-Bay twice a week, usually after dusk. On a recent trip, he used a cone-shape net to catch larval fishes.

"I can’t imagine a better way to spend the day," he said, smiling.

For larger fishes, Hayden and other Bowling Green researchers channel electrical currents into the lake to collect their samples.

Hayden said he would rather fish than polish hundreds of otoliths in the laboratory.

Once polished, Hayden and Miner take the ear stones to the University of Windsor in Canada, where a mass spectrometer determines the trace elements within each ring.

The otolith research community shares technology and discoveries.

Scientists in Ohio, Michigan, New York and Canada say they have a common goal — to protect the Lake Erie ecosystem.

"We have to share information across the border because the fishes don’t understand the border," said Brian Fryer, director of the Great Lakes Institute for Environmental Research at the University of Windsor.

The weather dictates how often researchers can collect on the lake, making for some frustrating weeks.

But Hayden, a fisherman at heart, said it’s worth it.

"The fishes are a resource and they bring in a lot of money," he said. "It’s in our best interest to conserve the fish."

 
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