The effects of salinity on the embryonic and larvae stage of Crassostrea iredalei
were investigated. Fertilised eggs and one day old D-larvae were subjected to salinities
ranging from 0 to 30 ppt at temperature of 30±2°C. At salinity lower than 10 ppt, 100%
mortality was observed. For embryo development, the highest survival was observed at
salinity 25 ppt with 80.9±2.2% survival with no significant difference compared to 15 and
30 ppt. Shell height and length were both greatest at salinity 30 ppt. Throughout the 11
days culture, the highest larval survival occurred at salinity 15 ppt with no significant
difference compared to all other salinities except 10 ppt. Larval shell sizes showed no
significant differences between salinities, except for 10 ppt. Optimum culture condition for
larvae growth are salinities ranging from 15 to 30 ppt whereby the larval of this species
can tolerate wider range of salinity compared to other oyster species and thus, making it a
competitive species to be cultured.
A small scale laboratory study was conducted to determine the effects of
salinity ranging from 15, 20, 25, 30, 35, 40, and 45 ppt on the filtration rates of juvenile
oyster Crassostrea iredalei with 25 ppt as the control. Three juvenile oysters (shell weight:
1.04 ± 0.12 g; shell length: 1.9 ± 0.2 cm; shell height: 1.9 ± 0.1 cm) were used to test the
filtration rates in each salinity over the course of 8 hours. The hourly filtration rates were
determined from the exponential decrease in algal (Chaetoceros calcitrans) concentration
as a function of time. The oyster in 35 ppt salinity produced the highest overall filtration
rate (FR2) with 134.06 ± 15.66 mL–1 hr–1 oyster–1 and the lowest overall filtration rate (FR2)
occurred in oyster exposed to 15 ppt and 45 ppt with 31.30 ± 6.90 mL–1 hr–1 oyster–1 and
32.11 ± 7.68 mL–1 hr–1 oyster–1
respectively throughout the 8 hours. The result from this
study can be useful for optimum oyster culturing and the oysters can be employed as a
natural biofilter in marine polyculture farming.