Triploid Grass Carp Evaluations in Private Waters:
a 1995 Summary

CLELL GUEST (Texas Parks and Wildlife Department, 6200 Hatchery Road, Ft. Worth, Texas 76114)

Data were collected from 1992 through 1995 to evaluate the effectiveness of triploid grass carp as a biological control of aquatic vegetation in Texas ponds. This study will continue through 1996. In 1992, 1993, and 1994, 40, 186, and 178 ponds were inspected prior to grass carp introduction. Study ponds are being inspected for two years following carp introduction. For the three sets of study ponds, initial total abundance of aquatic vegetation has averaged 50% coverage prior to fish introduction. Stocking rates of 1 to 7 fish/acre is probably too narrow of a range to determine their effects in this subjective type of study. The majority of the ponds were stocked at 5-7 fish/acre. Fish size at stocking and pond size effects were masked by plant types present. Small fish (6-9 inches total length) were usually stocked in the larger ponds which were typically infested with coontail and/or milfoil. Triploid grass carp have not controlled coontail in Texas ponds, but have controlled milfoil when combined with chemical treatments. When najas, chara, and algae were found alone in ponds, good control usually occurred; however, in mixed plant type ponds, variable results were frequent. When evaluating the effects each plant type regardless of other plant types present, it appears that chara, algae, and pondweed abundance has been reduced successfully (50% reduction) in 60% of the ponds they were found. Najas, the most frequently occurring plant type and plant type found in highest abundance in Texas ponds has been successfully controlled in 68% of the ponds it occurred. Pond size seems to be affecting the successful control of vegetation by triploid grass carp more than any other factor, with stocking rate having less affect. Fewer fish can be stocked in small ponds when stocking rates are based on pond size, but in the small study ponds, more fish are being stocked per vegetated acre than in large ponds. However, control of vegetation is less successful in these small ponds. Two factors probably contributing to this are: plant growth is enhanced in small shallow ponds, and plant type diversity is greater in the smaller ponds.

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For More Information Contact:

Clell Guest
Texas Chapter of the American Fisheries Society
6200 Hatchery Road, Ft. Worth, Texas 76114
Tel: 817-732-0761
Internet: tpwd2d@flash.net

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Copyright © 1996 Texas Chapter of the American Fisheries Society
Last modified: 03/08/07 01:08 PM