VANCOUVER, British Columbia -- Ecologists have long believed that fish tend to return to the same river where they hatched in order to spawn. But researchers at Ohio State University have determined that the old rule doesn't always apply -- not for Lake Erie walleye, at least.
Using a statistical analysis of chemicals found in walleye ear bones, the researchers were able to calculate the percentage of walleye hatched in the Sandusky and Maumee rivers that returned home to spawn, and the percentage that strayed elsewhere.
They discovered that almost all the walleye that spawned in the Maumee were hatched in the Maumee, but only two thirds of the walleye that spawned in the Sandusky were hatched in the Sandusky. Most of the remaining third had hatched in the Maumee.
The findings, which will be presented at the Joint Statistical Meeting in Vancouver, British Columbia on Thursday, August 5, will help wildlife officials determine which rivers may be at risk of overfishing and which may not.
Otoliths, commonly called "ear stones," are actually inner ear bones that help fish sense their balance and movement in the water. Similar structures perform the same function in the human ear.
"As fish grow, the otoliths grow, too," said Bethann Mangel Pflugeisen, who just earned her master's degree in statistics at Ohio State. "Every day, new layers are deposited on the outside of the otolith. Trace elements from the water become embedded in the layers, and ecologists can read these chemical 'signatures' to reconstruct the life history of a fish."
Otoliths contain rings -- similar to tree rings -- that mark the passage of the seasons. Scientists can sample the material between the rings to tell where a fish was living during that particular season.
The walleye is the Ohio state fish, and it is prized by commercial fisheries, recreational anglers, and seafood lovers. It can be found all over the Great Lakes, but thos
|Contact: Catherine Calder|
Ohio State University