Journal of the Marine Biological Association of India

Volume 18 Issue 1

Salinity tolerance and rate of filtration of the pearl oyster Pinctada fucata.

K. Alagarswami and A. C. C. Victor

Salinity tolerance and rate of filtration of the pearl oyster Pinctada fucata were studied during 1975-77. The oysters were experimented in salinities ranging from 14 to 58 %„. Although a truly marine form, the pearl oyster has been found to tolerate a wide range of salinity from 24 to 50%, for short durations of 2-3 days. Salinities below and beyond the above range caused mortality of oysters. The rate of mortality in the dilutions of 16,15 and 14 %o were 10, 50 and 100% respectively and mortality in higher concentrations of 52, 55 and 58 %o were 67,100 and 100% respectively.

In the normal sea water (salinity 34%,) the removal of neutral red in solution was 52.1 % in 2 hours and 92.6% in 8 hours. The rate of filtration was low in dilutions and the total filtration was bel w 25 % in the salinities of 14 and 20 %,. In the higher concentrations, filtration was 49.5, 53.7 and 41.8 % in the salinities of 44,50 and 57 %, respectively at the end of 4 hours.

In the Gulf of Mannar, where a pearl culture farm is located, the normal salinity range during 1974-76 was 32.15-35.58 %. An unusual incidence of dilution of sea water down to 15.69/^, occurred in the farm at Veppalodai in November 1977 due to heavy rainfall and floods m the rivers caused by an active north-east monsoon. However, this did not affect the oysters as the low saline condition did not last for more than a day.

Date : 30-04-1976