"Up to now, the only way to accurately determine a fish's age has been to kill the fish and examine the growth rings in its 'otolith,' or ear bone," he explained. "To remove the otolith, you first have to kill the fish, and with large predatory fish like muskies you just don't want to do that.
"I think we can get equally valid results by looking at the growth rings in the rays of a muskie's pelvic fins. Clipping off a piece of fin doesn't harm the fish, and if we can determine that the pelvic fin ray technique is accurate, we'll have a powerful new non-lethal research tool at our disposal."
Hansbarger plans to validate the technique by tagging young-of-the-year muskies, recapturing and fin-clipping them when they're older, and using information on the tags to determine if the rings on the pelvic fin rays match the fishes' age.
West Virginia is located near the southern edge of muskies' native range, a factor Hansbarger said should work in the new technique's favor. Muskies from more southerly climes grow faster than they do in Canada or the upper Midwest, and therefore have more widely spaced growth rings in their fin rays.
"The fish for my study went to Upper Mud River Lake and Mason Lake," he said. "I wanted to have northern and southern water bodies where I could recapture fish and compare the [growth-ring] formation in their pelvic fins."
The rest of the tagged fish went to Stonewall Jackson Lake, where DNR officials plan to equip marina operators with tag readers to determine the ages of recaptured muskies. Beginning in January, a 52-inch minimum size limit will go into effect at Stonewall, so almost all muskies caught will have to be released.
"Being able to use the tags to determine fishes' ages will give biologists a better idea of how fish are surviving, and how the lake's age structure is stacking up," Hansbarger said.
He called the advanced fingerling-tagging effort "a good project where a lot of people came together and worked for the good of the muskie-fishing resource."
"This is something to feel good about," he said.
Reach John McCoy at johnmc...@wvgazette.com or 304-348-1231.