THE IMPACT OF AN ABIOTIC VARIABLE, TEMPERATURE, ON LARVAE OF THE BLUE CRAB, CALLINECTES SAPIDUS RATHBUN, 1896 (BRACHYURA, PORTUNIDAE)

Reductions in the size of mature blue crabs, Callinectes sapidus, which are commercially harvested, are of concern to the aquaculture industry. Through their role in the production of viable offspring, aquaculturists focus their attention in particular on female crabs, although the phenomenon will, of course, also affect the males. Meanwhile, decreases in size at maturity throughout the crab population may be the result of temperature alterations, at present also due to global climate change. Temperature -based shifts in growth can lead to changes in reproductive efficiency, as well as in size and age at maturity. In this study, the effects of temperature on the moulting frequency of blue crabs were investigated and survival rates have been calculated. The purpose of this study was to investigate the temperature dependence of survival and of the moulting processes for blue crab larvae, and to determine the effect of increasing temperature on moulting. The stages from zoea-1 to zoea-5 were examined at 16, 22, 26 and 30(degrees)C. The results show that there is a significant difference in growth and moulting, depending on the rearing temperature. As the temperature increases, the interval between moulting days can be seen to be shortened, and increasingly so with the progress in the growth of the crabs. Moulting -interval days became less with the growth of the crabs. The effect of a rise in temperature on growth per moult is also significant, and along the temperature range tested the optimum temperature was found to be 26(degrees)C. A reduction in the length of the intermoult period was observed from the lowest to the optimum temperature, while a sudden, sharp increase in the intermoult period above 26(degrees)C was observed as well.