Habitat Research: Fish Community Response to Mechanical Harvesting of Aquatic Macrophytes

Objectives of this research is to test the hypothesis that an increase in the ratio of edge-to-surface area of dense macrophyte beds can significantly affect fish populations, angling harvest, and fish community structure.

Background

In many Wisconsin lakes, dense macrophyte beds limit the potential for angling, boating, and swimming. The problem has been exacerbated by Eurasian watermilf-oil, an introduced invasice species which forms dense mats of vegetation at the lake surface. It tends to become the dominant species, frequently exceeding 95% of the total macrophyte community. These monotypic mats generally cover a much larger surface area than mats formed by native species.

In terms of angler satisfaction, the problems encompass more than just limited accessibility. Changes in macrophyte diversity and macrophyte bed physical characteristics also affect the population and behavioral characteristics of various species of panfish and game fish.

With the increasing demands for water-based recreational opportunities, resource managers must find effective and efficient ways to meet these demands. Removing so-called aquatic weeds with mechanical harvesters or herbicides may improve conditions for boating, swimming, and even accessibility for angling, but their impacts on fish populations are not well understood.

This study will indicate how milfoil responds to cutting and removal. It will also yield information on the increased utilization of invertebrate food organisms by smaller fish. Cutting and removal should decrease the total area of milfoil coverage, while increasing edge habitat and invertebrate food resources. It may also stimulate the regrowth of native species and improve water quality.

For more information on this topic please contact:
Tim Larson (608) 635-8122

Associated Publications

Budd, J., R.A. Lillie, and P. Rasmussen. 1995. Morphological characteristics of the aquatic macrophyte, Myriophyllum spicatum L., in Fish Lake, Wisconsin. Journal of Freshwater Ecology 10:19-31.

Carpenter, S.R., P. Cunningham, S. Gafny, A. Munoz-del-Rio, N. Nibbelink, M. Olson, T. Pellett, C. Storlie, and A. Trebitz. 1995. Responses of bluegill to habitat manipulations: power to detect effects. North American Journal of Fisheries Management 15:517-19.

Carpenter, S.R., M. Olson, P. Cunningham, S. Gafny, N. Nibbelink, T. Pellett, C. Storlie, A. Trebitz, and K. Wilson. 1998. Macrophyte structure and growth of bluegill (Lepomis macrochirus): design of a multi-lake experiment. Pp. 217-27 in E. Jeppeson, Ma. Sondergaard, Mo. Sondergaard, and K. Christofferson, eds. The Structuring Role of Submerged Macrophytes in Lakes. Springer-Verlag, Berlin.

Lillie, R.A. 1996. A quantitative survey of the floating-leafed and submersed macrophytes of Fish Lake, Dane County, Wisconsin. Transactions of the Wisconsin Academy of Science, Arts, and Letters 84:111-25.

Lillie, R.A., and J. Budd. 1992. Habitat architecture of Myriophyllum spicatum L. as an index to habitat quality for fish and macroinvertebrates. Journal of Freshwater Ecology 7:113-25.

Lillie, R.A., J. Budd, and P.W. Rasmussen. 1997. Spatial and temporal variability in biomass density of Myriophyllum spicatum L. in a northern temperate lake. Hydrobiologia 347:69-74.

Lillie, R.A., and D. Helsel. 1997. A native weevil attacks Eurasian watermilfoil. Wisconsin Department of Natural Resources. Research and Management Findings 40.

Nibbelink, N.P., and S.R. Carpenter. 1998. Interlake variation in the growth and size structure of bluegill: inverse analysis of an individual-based mode. Canadian Journal of Fisheries and Aquatic Sciences 55:387-96.

Olson, M.H., S.R. Carpenter, P. Cunningham, S Gafny, B.R. Herwig, N.P. Nibbelink, T. Pellett, C. Storlie, A.S. Trebitz, and K.A. Wilson. 1998. Managing macrophytes to improve fish growth: a multi-lake experiment. Fisheries 23(2):6-12.

Pellett, T. D., ed. 1997. Pretreatment results of the Fish Lake Project: fishery and aquatic community responses to mechanical harvesting of macrophytes: evaluating edge effect. Wisconsin Department of Natural Resources. PUBL-SS-924-97.

Sloey D.J., T. D. Schenck, and R.P. Narf. 1997. Distribution of aquatic invertebrates within a dense bed of Eurasian watermilfoil, (Myriophyllum spicatum L.). Journal of Freshwater Ecology 12:303-13.

Storlie, C.H., T.D. Pellett, D.J. Sloey, and J.M.L. Unmuth. 1995. Some macrophyte, invertebrate, fish associations in a Myriophyllum spicatum lake: Will increasing the "edge" change anything? Pp. 263-72 in Proceedings of the 25^th Annual Meeting of the Aquatic Plant Control Research Program, U.S. Army Engineer Waterways Experiment Station, Vicksburg, MS.

Trebitz, A.S. 1995. Predicting bluegill and largemouth bass response to harvest of aquatic vegetation. University of Wisconsin-Madison. Ph.D. Thesis.

Trebitz, A., S. Carpenter, P. Cunningham, B. Johnson, R. Lillie, D. Marshall, T. Martin, R. Narf, T. Pellett, S. Stewart, C. Storlie, and J. Unmuth. 1997. A model of bluegill - largemouth bass interactions in relation to aquatic vegetation and its management. Ecological Modelling 94:139-56.

Trebitz, A., and N. Nibbelink. 1996. Effect of pattern of vegetation removal on growth of bluegill: a simple model . Canadian Journal of Fisheries and Aquatic Sciences 53:1844-51.

Unmuth, J.M.L., D.J. Sloey, and R.A. Lillie. In press. An evaluation of close-cut mechanical harvesting of Eurasian watermilfoil. Journal of Aquatic Plant Management.

Wilson, K., and S. Carpenter. 1997. Making the weedline work for your lake. Wisconsin Natural Resources 21(2):4-8.

Associated Publications in Preparation

Lillie, R.A. Temporal and spatial changes in milfoil distribution and biomass associated with weevils in Fish Lake, WI. To be published in the Journal of the Aquatic Plant Management as a contribution to the proceedings of a special session of the annual meeting of the Aquatic Plant Management Society. In review.

Lillie, R.A., J.M.L.Unmuth, D.W. Marshall, and D.S. Dreikosen. Temporal and spatial patterns of dissolved oxygen and temperature within dense stands of Eurasian watermilfoil, Myriophyllum spicatum L., in a northern, temperate lake. To be submitted to Journal of Freshwater Ecology. In preparation.

Sloey, D.J., T.D. Schenck, and R.P. Narf. Changes in largemouth bass (Micropterus salmoides) piscivory rates following an increase in edge habitat created through mechanical macrophyte harvesting. In revision.

Unmuth, J.M.L. Effects of aquatic plant manipulation on angling and fish in Fish Lake, Dane County, Wisconsin. University of Wisconsin-Stevens Point. M.S. Thesis. In preparation.

Unmuth, J.M., M.J. Hansen, and T.D. Pellett. Effects of close-cut mechanical harvesting on largemouth bass and bluegill populations in Fish Lake, Wisconsin. Submitted to the North American Journal of Fisheries Management

Unmuth, J.M., M.J. Hansen, and T.D. Pellett. Effects of close-cut mechanical harvesting on angling in Fish Lake, Wisconsin. In preparation.

Wilson, K.A., and J.J. Magnuson. Predation risk and structural complexity: unexpected results from alternate predators. Submitted to Ecology.