8 degrees. According to the aquaculture data, it is known that the normal seawater salinity is 8 degrees to 15 degrees, and the seawater salinity of cultured oysters is lower than 8 degrees and the height is 15 degrees, which is not conducive to the growth of oysters. Oysters have strong resistance to adversity, but their viability will be affected in the environment with too high or too low salinity. Too high or too low salinity will cause oyster to lose water or absorb too much water, and the mortality rate will increase.