Feeding Behavior, Food Consumption, Growth, and Survival of Hybrid Grass Carp (Hypophthalmichthys nobilis x Ctenopharyngodon idella) In South Dakota

Plant preference of yearling hybrids (Hypophthlmichthys nobilis X Ctenopharyngodon idella) was examined under control conditions at the Gavins Point National Fish Hatchery, Yankton, South Dakota and under field conditions in two stockwater impoundments in south-central South Dakota. IN feeding trials, conducted in a 0.07 ha hatchery pond, hybrid grass carp selected Najas guadalupensis, Chara sp. and Potamogeton pectinuatus. Ceratophyllum demersum and Myriophyllum spicatum were not consumed. Under field conditions N. guadalupensis also appeared to be preferred while C. demersum was not. Feeding behavior, daily consumption, growth, and survival were also evaluated in the two stockwater impoundments. Hybrids averaging 51g were stocked in the ponds at rates of 17 and 31 kg/ha. No discernible control of aquatic vegetation was attained by the hybrids at these stocking rates. Feeding activity of the hybrids was diurnal and took place primarily in shallow water. The hybrids fed most heavily from 0400 to 0800 and from 1600 to 2000. Total daily consumption was 44.0% of body weight at 23 C and 30.4% at 15 C. Several of the hybrids from 24 April 1982 to 18-19 September 1982 was 59.1 and 32.3% in Ponds 1 and 2 respectively. Hybrids surviving to the end of this period averaged 542g in Pond 1 and 591g in Pond 2, representing 3.3 and 3.6 g/day growth rates.