Damaged trees benefit lake's fish
Jan 27, 2013 (The Leader-Telegram - McClatchy-Tribune Information Services via COMTEX) --
Scattered about the shores of Half Moon Lake are recently felled trees -- not the act of a vandal with a chainsaw, but rather city workers with chainsaws, and a permit arranged by the local Department of Natural Resources fish manager Heath Benike.
Benike approached city officials after the May 24 wind storm wrecked havoc on the trees in Carson Park, and those surrounding Half Moon Lake. He wanted some of those damaged trees to be used for fish habitat.
"Heath found a small silver lining for us in the wake of the storm for some of the trees around Half Moon Lake," said Todd Chwala, superintendent of the city's Parks, Recreation and Forestry Department,
Benike marked 46 trees bordering the lake that were in strategic locations for fish habitat. They were either storm damaged or leaning over the lake. About 80 percent of them were "pretty severely beaten up" by the May storm, Chwala said.
Last week, with safe ice on the lake, city crews went out and cut down most of the trees, so they tumbled on the ice. Most were then attached to the bank and stump with a steel cable.
Much of Half Moon Lake lacks woody habitat near the shoreline of the lake, which is an important area for fish and wildlife, Benike said. He said he tried to design the "tree drop" to provide cover where it is lacking. "We've tried to spread them out so they weren't all in one location," he said. "When the ice goes out this spring, hopefully we'll have some nice, near-shore habitat for fish," Benike said.
Bass like to make their spawning beds near logs. Perch drape eggs on sticks. Bluegills are colonial nesters, but they also like to build their spawning beds near wood cover, he said. All kinds of small fish and recently hatched fish take refuge from predators among submerged branches, he said.
The above-water branches of the downed trees also provide habitat, Benike noted -- turtles bask on the logs, birds perch on the branches.
Chwala said it took little convincing for the city to go along with the project. About 80 percent of the trees Benike marked were "pretty well beaten up" by the wind storm, he said.
Mayo tree drop
This is not the first "tree drop" in the lake. In 2010 the city dropped about six trees in the lake behind Mayo Clinic Health System. The trees had been trimmed so they didn't obstruct the Mayo One helicopter when it used to land on a pad next to the lake. Those trees were dying or in poor health, said Steve Roscoe, the city's park maintenance supervisor. They attached the downed trees to their stumps with steel cables, as required by the DNR, but thieves have taken them. "It wasn't like one cable's missing. There were about six trees and all the cables were gone," he said. It would have required a hacksaw or bolt cutter to get them off, and they wouldn't be worth much for scrap metal, but they're gone," Roscoe said.
Although the DNR likes the habitat trees to be secured with cable, those trees have not gone anywhere, Roscoe said. The small, urban lake does not have a lot of current or big waves that would move trees, he said.
Last summer the city stopped pumping water into the lake, on orders from the DNR, after officials discovered that the well water contained high levels of phosphorus. The wells are in Owen Park near the Chippewa River. Because it was a dry year, the lake level dropped, Roscoe said. Now the pumps are running again and the lake is near normal water levels, he said. Water has begun flowing out of the outlet again.
A fish survey taken on the lake last year found an extremely high density of largemouth bass -- 60 bass per acre. "That's the highest I've seen in the state of Wisconsin," said Benike, He said when he worked in Barron County he considered 10 to 12 bass per acre typical for a bass lake.
But the high bass density is not necessarily a good thing, he said. The bass were small and slow growing, with few over the 14-inch size limit.
In a 2001 survey the DNR found only half as many bass -- 30 per acre -- still a high population, but with more big bass. "They had a much better size range then," he said.
Benike is proposing a change in the size limit from the statewide 14-inch minimum to a "slot-size" limit that would encourage anglers to keep more small bass. The "slot" would protect medium-sized bass, most likely from 14 to 18 inches, while encouraging anglers to keep 10- and 12-inch bass.
Knight can be reached at 715-830-5835, 800-236-7077 or email@example.com.
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