CROLL, S.L.*; WATTS, S.A.: The effect of temperature on feeding characteristics in two sympatric crayfish species

Crayfish are an integral component of many freshwater habitats. They often impact the environment through vegetative grazing, burrowing activities, and predation. The red swamp crayfish, <1>Procambarus clarkii (PC), and the white river crayfish, <1>P. zonangulus (PZ), are commonly found in the southeastern United States and are important in commercial culture activities. Because of their ecological and commercial importance throughout these temperate regions, the effects of temperature on feeding characteristics and, consequently, production are of interest. Consumption of a formulated diet, apparent dry matter digestibility (ADMD), and carbohydrate and protein absorption were examined after exposure for 3 weeks at 8, 14, 20, 26, or 32 C. Sex-specific differences were generally not found in either species. At 32 C, PC consumed significantly more feed (30 % body weight per d) than PZ (4 % body weight per d); consumption did not vary between the species at all other temperatures. Consumption averaged 6 and 7 % body weight per d at 26 C in PC and PZ, respectively, a temperature near their reported thermal optimum. Consumption was minimal at 8 C. ADMD ranged from 55-75% regardless of sex, species, temperature, or rate of consumption. Carbohydrate absorption efficiency increased in both species from approximately 20 % to 70 % as temperature increased from 8 to 32 C. In contrast, protein absorption efficiency decreased from 45 % to 5 % as temperature increased from 8 to 32 C. PC and PZ maintain a relatively constant consumption rate at a wide range of temperatures, but species-specific differences at high temperatures suggest that PC will have a potential growth advantage. These data suggest further that the protein:energy requirements for these species change with temperature.