Combined effect of temperature, salinity, and rearing density on the larval growth of the black shell strain and wild population of the Pacific oyster Crassostrea gigas

Abstract

Crassostrea gigas is a commercially important species which is the mostly widely cultured in the world. However, most of the oyster broodstock in China remains unselected. Through a 7-generation of selection on the shell color and growth traits of adult oysters, an excellent strain of C. gigas with black shell coloration and mantle has been developed. In order to facilitate the industrialized breeding, it is necessary to explore the growth performance of the black shell strain in larval stage and find out the optimal conditions for larval development. In this study, the accumulated growth rate and survival rate of the black shell strain and wild population of C. gigas larvae were measured respectively, and a central composite design as well as a response surface method was used to investigate the combined effect of temperature, salinity, and rearing density on the growth of both the two populations. No significant differences were found in survival rate between the two populations, and two model equations for the growth of the two populations were established. The optimizations of accumulated growth rate for two populations were explored. When the temperature, salinity, and rearing density was 25.14 °C, 30.28 psu, and 1.00 ind. ml−1, respectively, the accumulated growth rate for the black shell strain maximized 15.40 μm day−1. With a combination of temperature of 25.06 °C, salinity of 29.27 psu and rearing density of 1.00 ind. ml−1, the maximum value of accumulated growth rate for wild population was 13.20 μm day−1. Furthermore, the larval growth rates were compared between the black shell strain and wild population, and the larvae of the black shell strain significantly grew faster than those of wild population when temperature, salinity and rearing density in a suitable range.