A comparative study of the survival, growth, and gonad development of the diploid and triploid Pacific oyster, "Haida No.2" strain.

The Pacific oyster, Crassostrea gigas, is an important cultured species in the northern coastal areas of China. In recent years, the triploid oyster was popular worldwide because of its fast growth and high meat quality and has rapidly occupied a large portion of the oyster market. As a multi-generation selection strain, "Haida No.2" of C. gigas has good growth performance. At the same time, we have successfully obtained the triploid and tetraploid "Haida No.2." This study was conducted to evaluate the performance of the triploid of "Haida No.2" under different rearing environments. The results showed that there was no significant difference in fertilization rate and hatching rate between diploids and triploids, and so did the survival rate at the larval stage, while the cumulative survival rate of triploids was significantly lower than that of diploids. At grow-out stage, the growth and survival rate of triploids were significantly higher than diploids on day 420 at two sites; meanwhile, the triploid rate was slight decline but still kept a high level (96–98%) on 420 days at two sites. However, high gametogenesis and subsequent mass spawning of triploid females were observed at two sites (32% at Rongcheng and 54% at Rushan), and the fecundity of triploid females relative to diploid females was high (23.73% at Rongcheng and 41.15% at Rushan) under different rearing environments. Our results showed that the triploid of "Haida No.2" had better performance at grow-out stage than diploids. However, the phenomenon of high gametogenesis of triploid and spawning is not favorable for the industrialization of triploid oysters, and the mechanism of high gametogenesis of triploids needs further study. [ABSTRACT FROM AUTHOR]