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.
