Abstract

This study placed hatchling (0.5 g) Procambarus clarkii, at densities of 4 and 12 m-2, in enclosures (0.5 m2) within experimental crayfish ponds each month (for 6 months) after flooding-up in October. Crayfish weights were recorded at 6, 9, and 12 weeks post-stocking. The study was conducted over two consecutive seasons, and water temperature was recorded continuously. Crayfish growth was influenced by both stocking date and stocking density, with stocking date having the greatest influence. Crayfish in the low density treatment, averaged over all months, were 25% heavier. Mean weight and percentage of individuals reaching a minimum acceptable market size (15 g) after 12 weeks, averaged for both densities, were as follows: October, 16 g and 54%; November, 11 g and 16%; December, 6 g and 0%; January, 15 g and 50%; February, 23 g and 92%; and March, 24 g and 95%. Only with the March stocking date were more than 50% of the individuals 15 g or more after 9 weeks. Growth rate was significantly correlated with mean water temperature, with r equal to 0.91, 0.69, and 0.65 for 6, 9, and 12 weeks, respectively. A cumulative Celsius degree-day model, based on an estimated thermal minimum of 5°C for growth, was developed to provide estimates for the cumulative degree-day requirements (DD-5) necessary for 50% of P. clarkii to attain 15 g from a half-gram hatchling. The DD-5 estimates were 851 and 1002 for crayfish grown at 4 m-2 and 12 m-2, respectively.

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