Building a better musky: Butternut Lake used for brood stock
Written by Ironwood Daily Globe   
Sunday, 01 April 2007 05:45

By collecting musky eggs from different lakes where muskies have proven they can grow to large sizes and reproduce successfully on their own, Wisconsin fisheries biologists are hoping to improve Wisconsin's musky rearing and stocking program and provide better fishing for years to come.

Department of Natural Resources fisheries biologists are working with a University of Wisconsin-Stevens Point fish geneticist who helped them develop genetic criteria for selecting lakes for musky egg collection.

Dr. Brian Sloss, a geneticist at the UW-Stevens Point College of Natural Resources, helped DNR biologists develop criteria to select lakes for egg collection using factors such as documented natural reproduction and adequate number of fish. Trophy-fish potential is another factor considered when selecting brood source lakes.

Dr. Sloss also recommended annually rotating collection among the lakes that meet the criteria for providing eggs for hatchery production.

"The greater the genetic diversity among sources of stocked fingerlings, the greater the odds they will adapt to their new home, resist disease, and perhaps even spawn successfully as adults," said Dave Neuswanger, DNR fisheries supervisor for the Upper Chippewa Basin.

Following the criteria, biologists last year obtained all the fertilized eggs needed for fingerling production at the Governor Thompson Hatchery in Spooner from adult muskies on the Chippewa Flowage.

"During that operation, we mated an unprecedented number of individual females -- 26 of them -- up to 51 inches in length with multiple unique males up to 45 inches in length," Neuswanger said. "This ensured a healthy level of genetic diversity among the hatchery-produced 10- to 12-inch fingerlings stocked last fall throughout northwestern Wisconsin," he said.

This year, biologists chose Butternut Lake, near Park Falls in Price County, as the source of eggs for the DNR musky hatchery in Spooner. Neuswanger said that Butternut is one of the few lakes in northwestern Wisconsin that meet all the criteria recommended by Dr. Sloss for sources of muskellunge brood stock. Further, Butternut produced many trophy-class fish over 50 inches long until it became overpopulated in the early 1990s. More recently, body condition (plumpness), growth rate, and average size declined in the face of extreme competition for food among abundant adults.

"We propose to fix the overpopulation at Butternut by removing some adult fish surplus to our spawning needs. That will also help us start a new musky fishery in Lake Neshonoc near La Crosse," Neuswanger said. "As a source of eggs for hatchery production and adults to start a new fishery, Butternut is ideal because its adult muskellunge have the demonstrated potential to reach trophy size, and they have reproduced naturally at a high rate since 1995, even in the presence of northern pike."

Biologists initially considered moving a couple hundred adult muskies from Butternut Lake to Lac Courte Oreilles near Hayward. LCO currently has fewer muskies than desired. That plan was changed when tests showed substantial genetic differences between adult fish in the two lakes.

"We have no reason to believe there is anything wrong, genetically, with the fish in either lake," Neuswanger explained. "They simply appear to be different, and we thought it unwise to flood LCO with spawning adult fish from a different genetic stock at a time when biologists are trying to get the native stock at LCO to reproduce better on their own.

"Using Butternut Lake offspring will help maintain overall genetic diversity in northwestern Wisconsin," Neuswanger said. "The stocking of 10- to 12-inch fingerlings to maintain a musky fishery at LCO, where about 90 percent will die before reaching sexual maturity at age 6, poses far less risk to future natural reproduction at LCO than doubling the population instantly with a transfer of hundreds of spawning-age adults from Butternut Lake."

Neuswanger said he appreciates the help from the UW in moving the state's musky program forward. "I have worked in other states," said Neuswanger, "but none are applying the principles of muskellunge genetic stock conservation more progressively than Wisconsin right now, thanks in large part to Dr. Sloss."

Editor's note: More information about the genetic testing and other components of DNR efforts to assess and improve musky stocking practices is available in the August 2006 issue of Wisconsin Natural Resources magazine and on the musky management pages of the DNR Web site under "Draft Broodstock Management Plan" and "Genetic Research on Muskellunge in Wisconsin."
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