A university study on Lake Erie walleye may help scientists spot rivers that are at risk of overfishing. Researchers at Ohio State analyzed chemicals found in walleye ear bones, and were able to figure out which fish returned to their hatching site to spawn, and which ones went elsewhere, creating some rivers that are vulnerable to overfishing. The fish seem to be saying, "Can you hear me now?"Ecologists have long thought that most fish spawn in the same river where they hatched. But that's not always the case, with Lake Erie walleye at least. Using otoliths, or inner ear bones, the Ohio State University researchers found that a third of the fish that spawned in the Sandusky River had hatched in the Maumee River.
Otoliths, also called "ear stones," are used by fish to sense their balance and movement in the water. Humans use "ear stones" for the same thing. According to Bethann Mangel Pflugeisen, a master's student who worked on the study, trace elements from water become embedded in layers deposited on the outside of a fish's otolith. Those "chemical signatures" can be used to reconstruct the life history of a fish.
What does it all mean? Researchers say the findings will help wildlife officials determine whether rivers may be at risk of overfishing. The study could help managers set rules for catch limits. A river of walleye that don't stray from hatching to spawning is more vulnerable to overfishing, for instance, than a river that where fish hatched in other rivers come to spawn.
About 250 walleye were sampled for the study, during the spring of 2003, 2004 and 2005. The results were presented this week at the Joint Statistical Meeting in Vancouver, British Columbia.
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