 Larvae often settle on the shell of adults, and great masses of oysters can grow together to form oyster reefs.The optimum salinity for Pacific oysters is between 20 and 35 parts per thousand (ppt), and they can tolerate salinities as high as 38 ppt; at this level, however, reproduction is unlikely to occur.The Pacific oyster is also a very temperature tolerant species, as it can withstand a range from -1.8 to 35 °C.