Effect of salinity on survival, growth, and oxygen consumption of postlarvae (PL10-PL21) of Litopenaeus setiferus

The present study was done to establish the lethal salinity (LC50) and the effects of an abrupt change in the salinity on the oxygen consumption and t he growth of postlarvae (PL10-PL21) of Litopenaeus setiferus, and their int egration as assimilated energy. Postlarvae of L, setiferus presented a mean LC50 at 8 parts per thousand, and a time of response of 2 h. Thereafter, L C50 remained constant for the next 96 h. The effect of salinity on oxygen c onsumption and growth rate changed with the age of postlarvae. From PL10 to PL15, the highest oxygen consumption was obtained at 10 parts per thousand and the lowest ar:40 parts per thousand. During this time, growth rate inc reased with salinity with the maximum value in 40 parts per thousand and lo west at 10 parts per thousand. From PL15 to PL21, the highest oxygen consum ption was obtained at 30 and 40 parts per thousand. In 30 and 40 parts per thousand, the growth rate was lower than that observed in animals maintaine d in 10 parts per thousand. The assimilation-salinity relationship changed with the age of the organisms. From PLIO to PL15, assimilated energy increa sed with a decrease in the salinity, and from PL15 to PL21, assimilation in creased directly with an increase in the salinity. The inverse relationship between oxygen consumption and growth has been observed in other estuarine organisms and suggests that, when animals are found in an osmotically favo rable medium, the processes of capture and distribution of the ingested ene rgy are more efficient. These mechanisms change with age. From PL15 to PL21 , an increase in the salinity produced an increase in the assimilation This was a result of an increase in the respiratory efficiency and, as a conseq uence, a reduction of the net growth efficiency.