Effects of Salinity on the Survival of the Larval Stages of Penaeus monodon (Tiger Prawn)

Abstract

The tiger prawn, Penaeus monodon is cultured on a commercial basis in Sri Lanka. From the stage of spawning, through the larval stages, to the harvestable level controlled conditions are maintained especially with respect to food and quality of water. Salinity has long been considered a major factor which influences the survival and growth of penaeid shrimp during their culture cycle. In the culture of Penaeus monodon in Sri Lanka, full sea water (34ppt) is used throughout in the hatcheries. This paper reports on the effects of salinity upon the survival of the larval stages of P. monodon. In the salinity tolerance limits test the nauplii, zoea, mysis and postIarva stages showed 0% survival at the salinity levels of 0% sw, <60% sw, <70%sw, and <70% sw respectively. These experiments clearly showed that the larval stages at P. monodon have a lower lethal limit for salinity. 100% surivival ofnauplii, zoea, mysis and postIarva stages occurred at 40-100% sw, 90-100%sw, l00%sw respectively. Thus salinity tolerance become narrower as larval development proceeded. The salinity preferences of the larval stages were determined using a horizontal salinity gradient chamber. The nauplii stage showed equal preference for the salinity range from 50-100% sw. The zoea stage showed a preference for the 90-100% sw concentration. In the case of mysis and postlarva the preference was for the 100% sw. the salinity preference range become narrower as larval development proceeded.