Determination of optimum temperature and salinity for fertilization and hatching in the Chinese pearl oyster Pinctada martensii (Dunker)

Using central composite design and response surface methodology, the experiment of fertilization and hatching success in Pinctada martensii (phylum Mollusca, class Bivalvia, order Pterioida, family Pteriidae) was undertaken under laboratory conditions. The aim of the study was to (1) examine the influence of simultaneous variation in temperature and salinity on the fertilization and hatching successes in P. martensii; (2) model the relationship of fertilization and hatching to temperature and salinity; (3) determine the optimal temperature–salinity combination using the optimization technique. Results indicated that fertilization and hatching percentages declined with lower or higher temperatures and salinities. The linear and quadratic effects of temperature on both fertilization and hatching were highly significant (P < 0.01); the linear effect of salinity on fertilization was highly significant (P < 0.01) but not significant on hatching (P > 0.05); the quadratic effect of salinity on fertilization and hatching was highly significant (P < 0.01). Temperature was far more important than salinity in influencing the fertilization and hatching in P. martensii; the interaction between temperature and salinity on fertilization was significant (P < 0.05) but not significant on hatching (P > 0.05). The model equations for both fertilization and hatching toward temperature and salinity were established (P < 0.01), with their adequacy and predictive capability shown by the high coefficients of determination (R2 > 94%). More than 91% fertilization and 87% hatching could be attained at temperatures of 26–30 °C and salinities of 27–30 ppt. Through simultaneously maximizing the models derived with the aid of the statistical optimization technique, the optimal factor level combination of temperature and salinity was obtained: 27.91 °C/28.49 ppt, at which the greatest fertilization and hatching reached 92.50% and 87.74%, respectively, with the desirability as high as 0.998. It is anticipated that applying the optimal temperature–salinity combination to practice would improve the efficiency of seed production of P. martensii.

► The joint influence of two factors on fertilization and hatching was examined.
► The relationship of fertilization and hatching to two factors was modeled.
► The optimal temperature-salinity combination was determined.