Seventeen years of grass carp: an examination of vegetation management and collateral impacts in Ball Pond, New Fairfield, Connecticut

Abstract

ABSTRACTJune-Wells M, Simpkins T, Coleman AM, Henley W, Jacobs R, Aarrestad P, Buck G, Stevens C, Benson G. 2017. Seventeen years of grass carp: an examination of vegetation management and collateral impacts in Ball Pond, New Fairfield, Connecticut. Lake Reserve Manage. 33:84–100.Ball Pond is a 32 ha meso-eutrophic lake located in the Marble Valley of Connecticut. The local bedrock geology and watershed influences have resulted in a hardwater system with limited plant community diversity and an assemblage dominated by the nonnative species Myriophyllum spicatum. By 1996, M. spicatum dominated 32% of the waterbody, and residents were concerned their property values would fall as the recreational value of the lake diminished. In an attempt to remedy this issue, 400 grass carp (Ctenopharyngodon idella; ∼30 cm length) were released in 1997 at a rate of 38 per vegetated hectare. As a requirement of the state permit, the plant community, water quality, and the fish community were monitored throughout the initiative (1997–2014) to examine the impact of grass carp at multiple ecological levels of the lentic system. M. spicatum was significantly reduced in biomass and cover between 1997 and 2014, with no change in plant community richness. Concordant with the decrease in M. spicatum, the cover of Ceratophyllum demersum increased significantly and became more dominant in the plant community as M. spicatum was reduced. Our results also suggest there was no change in water quality or fish community density/diversity during the study period; however, fish community richness was reduced. Bluegill (Lepomis macrochirus) density and largemouth bass (Micropterus salmoides) size distribution both increased during this study. We assert that grass carp can be an effective approach to nonnative plant management in a northern meso-eutrophic lake.