Phenotypic analysis in the Chilean oyster, Ostrea chilensis Philippi 1845: relationship between juvenile and adult growth rates

Abstract. The Chilean oyster, Ostrea chilensis Philippi, shows high phenotypic variability for growth rate within populations. In order to determine if the serial correlation of growth rate in oysters is positive, the correlation between shell height and live weight at different stages of the life cycle in a cohort of the Chilean oyster was estimated. Four size groups of individually tagged oysters selected on the basis of their shell heights were examined. The relationships for juvenile and adult oysters were found to be positively correlated throughout the study period. The correlation coefficients ranged from r = 0.28 to r = 0.83. For shell height the coefficient of determination for market size oysters was higher in 2-year-old (r²=0.88) than in 1-year-old oysters (r²=0.09). Shell height and live weight were more highly correlated at later stages of the life cycle. The results indicate that 2-year-old oysters have a size that is indicative of performance to market size and hence is an appropriate age to select the parents to be used in breeding programmes to improve the growth rate in O. chilensis . A high mortality was detected after the natural spawning period. A physiological stress hypothesis is proposed to explain the high summer mortality in O. chilensis in the Quempillen estuary, southern Chile.