Aeration systems preventing fish kills on dozens of lakes

Discussion in 'Frontpage News' started by Steve, Feb 8, 2008.

  1. Steve

    Steve Staff Member

    Aeration systems preventing fish kills on dozens of lakes

    PARK FALLS – Many lakes in Wisconsin suffer from a problem known as winterkill of fish. Commonly called 'freeze-out,' a winterkill occurs when fish die as a result of low oxygen levels during the ice-covered period.
    But there is a fix.
    This winter, Department of Natural Resources fishery biologists are using mechanical aerating systems on dozens of lakes that have historically suffered winterkill to prevent problems and increase the number of fishable waters.
    Winterkill starts when ice cover cuts off the supply of oxygen entering lakes from the atmosphere and oxygen production within the lake, itself, decreases as deep snow blocks out light needed by algae and other plants to produce oxygen, according to Skip Sommerfeldt, DNR fish biologist in Park Falls.
    Aeration creates an open-water area during ice cover, allowing oxygen uptake by the lake. It has been an effective tool to deal with low-oxygen problems on more than 30 lakes across northern Wisconsin and more throughout the state.
    Within the Chequamegon-Nicolet National Forest alone, winter aeration has helped alleviate winterkill on 11 waters that total more than 4,200 acres, Sommerfeldt says.
    The DNR works with other agencies, local units of government and lake associations in maintaining aeration systems. The systems run on different kinds of power, including wind, solar, diesel and electric power.
    One recently installed system -- on Little Clam Lake in Ashland County – illustrates the benefits of these partnerships. Historically, the 144-acre seepage lake supported good populations of largemouth bass and panfish, but severe winterkills in 1996 and again in 2001 decimated the fishery.
    The DNR and U.S. Forest Service teamed up in 2004 to install a diffused-air aeration system on the lake that uses an electric air blower housed in a shore-based shelter. The blower forces air through galvanized pipe to a series of plastic diffuser lines laid onto the lake bottom. Air is bubbled through the lines to circulate the water and create a large open-water area during ice cover, providing oxygen to the lake.
    The lake was stocked with largemouth bass in 2004 and as of summer 2007, the bass had re-established a moderate population and anglers are catching bass 14 inches and larger.
    Self-sufficient systems that use solar and wind power have also been used on a few remote lakes far from the power grid. Solar-powered systems use an array of photovoltaic panels that supply power to a large storage battery. This battery then powers one or two small air pumps that deliver air into diffuser lines on the lake bottom.
    Wind aerators use a turbine to turn a propeller positioned just under the surface of the water. The spinning propeller pulls the lake water up from the bottom and melts the ice cover around the floating unit.
    The major drawback to these “green” systems is their dependency on sunshine or wind, which are often limited during winter months. Such ‘green’ systems are used mainly on small lakes where they provide a small refuge area for fish.
    All open-water areas are clearly marked with rope and reflective streamers held a few feet above the surface of the ice with wooden or plastic poles planted in the ice. Anglers, snow mobilers, hikers and other recreationalists should be cautious though as heavy winds, blowing snow and warm thaws may hinder the ability to see the barricades.
    When you see the barricades, remember they’re there to make fishing better this coming season.
    FOR MORE INFORMATION CONTACT: Skip Sommerfeldt (715) 762-1357