April 13, 2011
DNR STUDIES MUSKIE GROWTH IN LAKE WEBSTER
NORTH WEBSTER - A fish-tagging study being done by the DNR Division of Fish & Wildlife is shedding new light on how fast muskies grow in Lake Webster.
The results could affect the number of muskies stocked in the popular 774-acre lake in northern Kosciusko County. The results will also help DNR fisheries biologists determine if the 36-inch minimum size limit should be increased.
"Based on what we know already, Lake Webster has one of the densest populations of muskies in the Midwest," said Jed Pearson, DNR fisheries biologist for the area. "That's because we stock fingerling muskies each year in the lake at the rate of five per acre."
Other states typically stock one or two muskies per acre and sometimes do so every other year.
"What we don't know is whether the high density of muskies is affecting their growth," Pearson said. "A lake can hold only so many fish. When fish densities get too high, there may not be enough food to go around."
According to Pearson, some anglers claim the average size of muskies in Lake Webster is declining and fewer trophy-size muskies, those more than 46 inches long, are being caught.
Although length data recorded each spring from adult muskies captured during egg-taking operations do not back the claim, DNR biologists are taking a closer look at muskie growth in Lake Webster.
"Adult muskies average around 36 inches long but we occasionally catch some over 46 inches long during our hatchery egg-taking operations in spring," Pearson said. "What we want to know is how much a muskie grows each year and how its growth rate in Webster compares to other lakes."
To study muskie growth, Pearson has tagged more than 1,300 muskies with tiny PIT (passive integrated transponder) tags since 2005. Each fish is measured before the tag is inserted into muscle tissue along the dorsal fin. The tag has a unique numerical code that's read with a special electronic scanner. By noting changes in size from when a muskie is first tagged compared to when it is recaptured, biologists get an accurate account of how much the fish grew.
"Although we're just now getting long-term data on growth, we've already seen a big difference between male and female muskies," Pearson said.
Most male muskies stop growing after they reach 36 inches long. In contrast, females continue to grow about 1-2 inches per year after they reach 36 inches. Biologists call this "sexual dimorphic growth." They think it is an evolutionary adaptation in how a fish uses energy and helps the species survive and reproduce. The difference has management implications.
This means we may want to ignore the males. For management decisions, we plan to focus on how big the females grow," Pearson said. "As long as female muskies get bigger at normal rates, we don't think there is growth problem."
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