The Importance of the Rate of Aeration in Hatchery Cultures of the Larvae of Ostrea Edulis L.

Abstract

The effect of aerating cultures of the larvae of Ostrea edulis at various rates of air flow has been investigated using three culture vessels of different capacity but with similar proportions. It was found that aeration significantly improved both the growth of larvae and the rate of development of eyespots. Each type of vessel had an optimum air flow requirement and this increased with the capacity of the container. Larval growth and rate of development in 751 vessels was improved by increasing the number of aerating jets from one to five. It is suggested that the increased growth rate of larvae cultured at the optimum rate of aeration was indirectly responsible for the observed improvement in the rate of development of eyespots. The relationship between aeration and intensity of settlement was not clearly established. Suspended spat collectors were found to be unsatisfactory at high levels of aeration, since they trapped air bubbles. As aeration was raised to the optimum an increased proportion of larvae settled on collectors clamped to the bottom of vessels. Aeration of cultures may beneficially affect larvae by evenly distributing the food throughout the water, but it is more likely that the energy conserved by the larvae due to their passive maintenance in the water column by turbulent currents may be used for the building of food reserves and body tissues.