Effects of Microalgal Diets on the Growth and Survival of Larvae and Post-Larvae of the Basket Cockle, Clinocardium Nuttallii

The nutritional value of four microalgal species: Chaetoceros muelleri, Pavlova lutheri, Tahitian strain of Isochrysis sp. (TISO), and Thalassiosira pseudonana in single- and bi-species diets was evaluated for larvae and post-larvae of the basket cockle, Clinocardium nuttallii. 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 Chaetoceros muelleri. In another feeding experiment, the microalga Tetraselmis suecica was tested singly and in combination with TISO. Results showed that the food value of Tetraselmis suecica alone was poor for both larvae and post-larvae. In contrast, the mixed-species diet of Tetraselmis suecica 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 Clinocardium nuttallii seed, a single-species diet of TISO is the best for the larvae and a single-species diet of Chaetoceros muelleri 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.