Effects of microalgal diets on the growth and survival of larvae and post-larvae of the basket cockle, Clinocardiumnuttallii

The nutritional value of four microalgal species: Chaetocerosmuelleri, Pavlovalutheri, Tahitian strain of Isochrysis sp. (TISO), and Thalassiosirapseudonana in single- and bi-species diets was evaluated for larvae and post-larvae of the basket cockle, Clinocardiumnuttallii. Larval shell growth and metamorphic rate were found to be the greatest with both single- and mixed-species diets comprising TISO. For the post-larvae, however, optimal shell growth was observed in both single- and mixed-species diets containing Chaetocerosmuelleri. In another feeding experiment, the microalga Tetraselmissuecica was tested singly and in combination with TISO. Results showed that the food value of Tetraselmissuecica alone was poor for both larvae and post-larvae. In contrast, the mixed-species diet of Tetraselmissuecica and TISO resulted in significantly improved larval and post-larval growth, similar to the respective best (control) diets as identified in the first experiment. It is concluded that, for the hatchery production of Clinocardiumnuttallii seed, a single-species diet of TISO is the best for the larvae and a single-species diet of Chaetocerosmuelleri is the best for the post-larvae. A nutritional transition period during which both the microalgal species may be required, is also suggested for the hatchery production of basket cockle seed.