Use of Triploid Grass Carp to Reduce Aquatic Macrophyte Abundance in Recreational Fishing Ponds

Triploid grass carp (Ctenopharyngodon idella) were stocked at densities of 25 (low), 50 (medium), and 75 (high) fish/vegetated hectare into 9 0.16- to 2.83-ha Texas panhandle ponds to evaluate stocking densities that may reduce, but not eradicate, submersed aquatic macrophytes. Prior to stocking, the ponds had 50%-100% areal coverage of macrophytes. The macrophyte communities included Chara sp., Ceratophyllum demersum, Myriophyllum spicatum, Najas guadalupensis, and Potamogeton spp. The high stocking density eliminated macrophytes in ≤ 13 months. Low stocking densities did not reduce areal coverage of aquatic vegetation 2 or 5 years after stocking. Triploid grass carp stocked at medium densities reduced areal coverage of macrophytes by 27% after 2 years and 42% after 5 years. Our results indicate that triploid grass carp can reduce macrophytes without eradicating them and percentage areal coverage is an effective basis for prescribing stocking rate.

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