MANAGING MACROPHYTES TO IMPROVE FISH GROWTH - A MULTI-LAKE EXPERIMENT

Macrophyte harvesting often has been suggested as a way to improve fis h growth and size structure in lakes with high densities of submergent macrophytes and stunted fish populations. However, previous experimen tal tests have provided no clear consensus on whether the technique wo rks for management. We conducted a series of whole-lake manipulations to test the effects of macrophyte removal on growth of bluegill and la rgemouth bass. Wie selected four lakes in southern and central Wiscons in for experimental manipulation and nine others for controls. In Augu st 1994, we removed macrophytes from approximately 20% of the littoral zone by cutting a series of evenly spaced, deep channels throughout e ach treatment lake. In the first year after manipulation, we observed substantially increased growth rates of some age classes of both blueg ill and largemouth bass in treatment lakes relative to controls. Growt h rates of other age classes were less responsive to manipulation. We observed increased bluegill and largemouth bass growth despite rapid r egrowth of macrophytes in our treatment lakes. By May 1996, fewer than 25% of the channels remained. Our resulted suggest that harvesting ma crophytes in a series of deep channels may be a valuable tool for inte grated management of fish and macrophytes.