Survival and metamorphosis of Penaeus monodon larvae at different salinity levels.

Abstract

The survival rates of Penaeus monodon nauplii, protozoea and mysis abruptly exposed to salinity of 12, 16, 20, 24, 28, 36, 40 and 50 ppt were determined and compared. Larvae kept at 32 ppt, the spawning or initial rearing salinity, served as the control. The effect of the salinity treatments on the rate of metamorphosis of each larval stage was also investigated by determining and comparing the time needed for 50% of the larvae to molt to the succeeding stage (MT50).

Results showed that at the naupli stage, significantly higher (P<0.01) survival was obtained at 32 and 36 than at 28 ppt. However, survival at 28 ppt was still significantly higher than in the rest of the treatments. The MT50s at salinity levels of 28 to 36 ppt were similar. At the protozoeal stage, similar survival and MT50 values were obtained at 28 to 40 ppt. In all other test salinities, total mortality of the protozoea occurred. Within the salinity range of 20 to 36 ppt, the mysis exhibited similar survival rates but metamorphosis was significantly faster at 28 and 32 ppt, as shown by the lower MT50 values.