Growth, survival, haemolymph osmolality and organosomatic indices of the western king prawn (Penaeus latisulcatus Kishinouye, 1896) reared at different salinities

Abstract

The growth, survival, haemolymph osmolality and organosomatic indices of the western king prawn, Penaeus latisulcatus, (2.95±0.26 g mean initial weight), were measured when reared at 10, 22, 34 and 46 ppt salinity for 60 days. Mean final weight, total length and specific growth rate (SGR) of the prawns were highest at 34 ppt. Rearing at different salinities did not alter moult increments and intermoult periods of the prawns. One hundred percent mortalities were observed at 10 ppt.

Survival was highest at 22 ppt and food conversion ratios were significantly lowest (P<0.0.5) in prawns cultured at 22 and 34 ppt. Haemolymph osmolality increased with the increase in medium salinity and physiological age of the prawns. Isosmotic points calculated from regression between haemolymph and medium osmolality were 28.87, 29.46 and 31.73 ppt at 0, 20 and 60 days of culture, when body weights were 2.95±0.26, 4.02±0.47, 5.79±0.64 g respectively. After 60 days of culturing, hepatopancreatic moisture levels increased with the increase in salinity, whereas tail moisture levels remained unchanged. Wet and dry hepatosomatic indices were highest at 22 ppt. Wet tail muscle index was highest at 34 ppt, whereas dry tail muscle index did not change by any salinity levels. The results suggest that the optimum salinity range for rearing western king prawns ranges from 22 to 34 ppt and 10 ppt was unsuitable for culture.