Egg and larval quality criteria as predictive measures for juvenile production in turbot ( Scophthalmus maximus L.)

Although much effort has been made to evaluate criteria for marine egg and larval quality, the significance of poor egg quality for the results in the final juvenile production has not been clarified. The aim of our experiments with turbot ( Scophthalmus maximus) was to determine whether the initially observed egg quality affected offspring viability and normal development up to the juvenile stage. Eggs from each of six individual females were divided into three replicate groups, and the eggs in each replicate was quality evaluated according to fertilization rates and the ratio of normal cell cleavages (blastomere morphology) at the 8–32 cell stage. The condition of yolk-sac larvae was tested by an acute high salinity stress test, and the larvae were fed according to our standard feeding regime with microalgae, enriched rotifers and Artemia nauplii. Significant positive correlations were found between observed egg quality characteristics and hatching rates, larval tolerance to acute stress, and to survival, metamorphosis and juvenile pigmentation. Larvae hatching from poor quality egg groups thus had a lower viability and were less able to develop normally to the juvenile stage than larvae from good quality egg groups. Our conclusion is that egg quality observed as fertilization rate and rates of normal blastomeres at early egg stages may be a useful predictive tool for evaluation of the potential juvenile production in turbot.