Management Implications of Post-Stocking Survival of Grass Carp

We estimated post-stocking survival of grass carp from mark-recapture models designed for radio-tagged animals, and characterized relationships between survival and factors under the control of management, such as stocking locations and size at stocking.  We used grass carp from a wide range of lengths (352-573 mm) and weights (403-1920 g) at an annual stocking event in Lake Gaston, VA.  Post-stocking survival of grass carp varied throughout the year, and the probability (±SE) of survival to the end of the first year was 0.57(±0.10).  Grass carp survival varied between stocking locations, and was twice as high in the upper reservoir (0.87±0.09) than in the lower reservoir (0.43±0.11).   Differences in survival between stocking locations suggest that cost-effectiveness of grass carp stocking could be improved by focusing stocking efforts in specific regions of the lake.  None of the models developed in this study that incorporated grass carp size (length and weight) or condition factor of stocked fish accounted for a meaningful amount of the total model weights.  These results suggest that costs of grass carp stocking could be reduced in Lake Gaston by using a smaller minimum stocking size (352 mm, TL) than is commonly referred to in the literature (450 mm, TL).