This study was conducted to evaluate the effects of different ambient water temperatures on growth and population structure of freshwater prawns raised under standardized culture conditions, Juvenile prawns averaging 0.26 +/- 0.14 g were stocked into seven 0.04 ha ponds at two study sites. Three ponds were located in Kentucky (KSU:latitude 38 degrees 12') with seasonal water temperatures averaging 24-26 degrees C. Four ponds were located in Mississippi (MSU:latitude 33 degrees 28') with a seasonal average of approximately 30 degrees C, Prawn stocking, sampling, and harvest dates were identical at both locations. Juvenile prawns were single source and were harvested from the same nursery tank for stocking at both locations. The diet used at both sites was from a single production run and was stored under refrigerated conditions. Prawns at both sites were fed twice daily according to a computer generated feeding schedule, Beginning approximately 8 weeks prior to harvest, sampled prawns were also individually identified according to sexual morphotype, At harvest (117 days after stocking) all prawns at both sites were counted, morphotyped, and weighed, Prawn weights were higher at the more northerly site al all samples after 42 days post-stocking. When sampled 64 days post-stocking (5 August) no sexually mature male or females were found, Mature morphotypes were first captured in the Day 83 sampling (25 August). In the Day 106 sampling (16 September), there were no significant differences (P > 0.05) in numbers or weights of the three male morphotypes between sites. However, among females there were significantly fewer (P less than or equal to 0.01) berried females at KSU with their average weights being significantly greater (P less than or equal to 0.05) than those at MSU (35 g and 31 g, respectively). At harvest(Day 117: 27 September) KSU had significantly (P less than or equal to 0.05) fewer berried females (32%) and more virgins (45%) than MSU (56% and 25%, respectively). Berried females at KSU weighed significantly more than at MSU (33 g and 26 g, respectively). There were no statistically significant differences (P > 0.05) between the two sites in prawn survival (83%), average weight (35 g), and feed conversion (2.3). Production was significantly greater (P less than or equal to 0.01) at KSU (1261 kg ha(-1)) than MSU (1091 kg ha(-1)) largely reflecting higher average weights of some morphotypes and slightly higher survivals. Differences in proportions and sizes of female morphotypes probably indicate delayed sexual maturation at the more northerly site, prolonging somatic growth which normally ceases when food energies an redirected to reproductive activities.
