Manipulated yeast diets as a partial algal substitute for the nursery culture of the hard clam <i>Mercenaria mercenaria</i>

Rearing bivalve molluscs in commercial hatchery and nursery systems has so far relied on the production of live algae, which is costly and often unpredictable. Therefore the development of satisfactory artificial diet would greatly reduce the operating costs of bivalve operations. The development of techniques to improve the nutritional composition and digestibility of yeasts resulted in a product with great potential as a substitute for unicellular algae. Previous work on the Manila clam Tapes semidecussata showed that replacing 80% of the algae by these manipulated yeasts resulted in growth rates of 64 to 93% in comparison with the growth rate obtained for the algal control. In the present study a standard culture test for evaluating algal substitutes for the hard clam Mercenaria mercenaria is proposed. The results of the first experiments on the partial replacement of the algae by yeast diets are reported