BOWLING GREEN, O.—A small bone in the heads of fish could reveal to researchers where important sport and commercial fish have spawned and where they are spending their adult lives.

Bowling Green State University biologists and geologists are collaborating on a study of yellow perch in Lake Erie to see if the otolith—a small bone that helps fish maintain their balance—is a reliable source of encoded information on their spawning and migratory habits. The results could help the Ohio Department of Natural Resources focus its conservation and management efforts on the critical habitats of yellow perch and other sport fish such as walleye, white bass and smallmouth bass.

Sport fishing is a major recreational activity on Lake Erie and a prime economic driver of the coastal tourism industry. Lake Erie fishing traditionally has contributed about $500 million per year to Ohio's economy, according to Ohio Sea Grant data. A 1999 Sea Grant study of recreational boating in Ohio estimated that over half of Ohio's $1.3 billion boating-related spending was connected to Lake Erie fishing.

But the industries supported by Ohio's sport and commercial fisheries have experienced economic declines in recent years, due in part to ecological changes in Lake Erie that have affected food supplies and altered fish distribution and behavior.

Several BGSU research projects are aimed at helping to identify and solve those problems. In one of them, Dr. John Farver, an associate professor of geology, and Dr. Jeffrey Miner, an associate professor of biology, have devised a series of experiments in the lake and laboratory to look for a chemical signature in yellow perch otoliths. The project is underwritten by a $270,000, three-year grant from the Ohio Sea Grant program of the U.S. National Oceanic and Atmospheric Administration.

“We don't really know where the fish come from and where they are going,” says Todd Hayden, a second-year doctoral biology student from Mechanicsburg, Ohio, who is heading up the project. Yellow perch spawn throughout the western basin of Lake Erie and near shore areas of the central basin near Cleveland, and then distribute themselves throughout the lake, where they seek an area with plentiful food supply in which to live out their lives.

“If we can discover which are the most fertile spawning grounds, that information can help the DNR set better fishing limits on those areas in the spring in order for the area to continue to be a strong provider of fish,” Hayden said.

“The otolith is really more of a rock than a bone,” he explained. “It is made up of elements like strontium, magnesium and manganese, but mostly calcium as in bone. The analytical technique we use was developed by geologists and involves using a laser ablation inductively coupled mass spectrometer.” Because BGSU does not own that instrument, the researchers are collaborating with the University of Windsor to analyze their samples.

According to Hayden, “Otoliths are like the rings in a tree trunk. They grow more in summer and contain the chemical elements of the environments the fish pass through.   If these rings turn out to be reliable indicators, we're really onto something.”

The technique could be used by aquatic ecologists everywhere to track the movement of fish and help conserve habitat. In addition, the otoliths provide a record of when persistent bioaccumulating toxic metals such as lead and mercury were absorbed. Because consumption of those metals impacts human health, the otolith may also provide valuable information on water quality in critical habitats of important fish.

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(Posted August 24, 2005)