Abstract
Low-density stockings of triploid grass carp Ctenopharyngodon idella were evaluated to determine their ability to control nuisance submersed vegetation in small sportfishing impoundments. Triploid grass carp were stocked into four small impoundments at densities ranging from 4/surface hectare to 12.5/surface hectare. Submersed vegetation was monitored from July 1991 through July 1993. Sportfish communities were sampled seasonally from the 1991 summer through the 1993 winter. At a density of 7.5 triploid grass carp/surface hectare southern naiad Najas guadalupensis was removed in one growing season from an impoundment containing only southern naiad. In a mixed vegetation community southern naiad nearly was eliminated in one growing season at a density of 7.5 triploid grass carp/surface hectare. However, the standing-crop biomass of coontail Ceratophyllum demersum did not change. Control of coontail was attained in 1993, the second growing season, after increasing the stocking density to 12.5 triploid grass carp/surface hectare. A reduction in submersed vegetation standing-crop biomass was noted in 1993 for two impoundments stocked at a rate of 4 triploid grass carp/surface hectare. However, only in one of the two impoundments was it believed that the submersed vegetation was at the desired level of control. It appears that low-density stockings of triploid grass carp may provide the desired control of nuisance submersed vegetation in small sportfishing impoundments. Species of submersed vegetation present and the density of the vegetation present must be considered when making triploid grass carp stocking recommendations. Sportfish communities changed little during the project. More pronounced changes in the sportfish communities may occur with time. Long-term monitoring will be needed to completely assess any impacts on sportfish communities caused by low-density introductions of triploid grass carp.
Blackwell, Brian Gene (1993). An evaluation of low-density introductions of triploid grass carp in vegetated small sportfishing impoundments. Master's thesis, Texas A&M University. Available electronically from
https : / /hdl .handle .net /1969 .1 /ETD -TAMU -1993 -THESIS -B632.