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

  • Published source details June-Wells M., Simpkins T., Coleman A.M., 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 and Reservoir Management, 33, 84-100.


Action: Introduce organisms to control problematic plants

A before-and-after study in 1996–2014  of a lake invaded by Eurasian watermilfoil Myriophyllum spicatum in Connecticut, USA (June-Wells et al. 2017) found that after introducing grass carp Ctenopharyngodon idella, there were significant changes in the submerged macrophyte community  composition, and an increase in submerged macrophyte richness. In 1996, watermilfoil beds covered 32% of lake area. Grass carp were first introduced in 1997. Over the 17 following years, the overall submerged macrophyte community composition changed significantly (data reported as graphical analyses). More specifically, the abundance of watermilfoil declined: from 107 g/m2 to 16 g/m2 above-ground biomass between 1997 and 2003, and from 16% to <1% cover between 2004 and 2014. From 2004, there were also significant changes in the abundance of native coontail Ceratophyllum demersum (increase from 12% to 72% cover) and guppy grass Najas guadalupensis (decrease; data not reported). The lake contained three submerged macrophyte species in 1997–2003 and four species in 2004–2014. Methods: From 1997, sterile grass carp were stocked into a 32-ha, freshwater lake: 400 carp in 1997, then supplemental stockings of 470 carp (total) between 2004 and 2013. The lake contained ≥151 carp each year from 1997. Submerged macrophytes were surveyed along five transects, in water ≤4 m deep, each year between 1997 and 2014. Until 2003, macrophytes were cut from 1 m2 quadrats, then identified, dried and weighed. After 2003, species and their cover were recorded visually.

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