Broodstock management of Crassostrea gigas: II. Broodstock conditioning to maximize larval survival

The results of time-course conditioning trials indicate that there is an optimum conditioning interval during which the proportion of viable gametes is at a maximum. When matings are accomplished before or after this optimum interval, reduced gamete viability results. In this case, spawning and fertilization may appear to be normal, but setting success is substantially reduced.The degree of conditioning required to reach this optimum window is dependent on the stage of gonadal development in the broodstock when conditioning is started, and reflects substantial seasonal variation, which is repeated on an annual cyclic basis.Performance of the larval rearing system, reflected in the proportion of ova which survive to the spat stage, may be substantially improved by managing broodstock conditioning to maximize the proportion of viable gametes. This may be accomplished by empirical observation of the annual gonadal cycle in the area where the broodstock is maintained, and then determining the optimum conditioning interval for the various seasons.