Combined effects of temperature, salinity and rearing density on the larval growth and survival of the diploid, triploid and tetraploid of the Pacific oyster Crassostrea gigas

The Pacific oyster, Crassostrea gigas, is a commercially important species, which is widely cultured in the world. In recent years, triploid cultivation of C. gigas has gradually emerged due to the advantages of poor fertility and rapid growth in China. However, the adaptation of triploid and tetraploid larvae to temperature, salinity and rearing density has not been studied. A central composite design and a response surface method were used to analyze the combined effects of temperature, salinity and rearing density on growth and survival of triploid and tetraploid larvae. Temperature, salinity and rearing density exerted significant effects on larvae growth and survival of triploid and tetraploid. Rearing density was identified as the most significant negative factor affecting the growth and survival of three populations. The reliable models on accumulated growth rate (AGR) and survival rate (SR) of three populations were obtained. The optimal conditions for larval development in the three populations were achieved by simultaneously maximizing growth and survival models. In diploids, the maximum AGR of 13.92 μm day−1 and the maximum SR of 65.73 were achieved at 23.66 °C / 28.47 psu / 2.23 ind.ml−1 with a value of desirability being 100%. In triploids, the maximum AGR of 15.82 μm day−1 and the maximum SR of 69.26 were achieved at 23.16 °C / 30.67 psu / 2.15 ind.ml−1 with a value of desirability being 100%. In tetraploids, the maximum AGR of 10.75 μm day−1 and the maximum SR of 46.29 were achieved at the 25.48 °C / 28.94 psu / 2.00 ind.ml−1 with a value of desirability being 95%. This study provides valuable new insights into refining the production efficiency of C. gigas larvae of different ploidy.