The culture of the diatom Chaetoceros gracilis and its use as a food for penaeid protozoeal larvae

The use of the solitary diatom Chaetoceros gracilis as the exclusive food for Penaeus stylirostris and P. vannamei protozoeal larvae produced high survival rates in 40 m³ tanks at a commercial shrimp hatchery. The diatom was maintained in the laboratory at 25–26°C and grew vigorously in the hatchery tanks at 28–30°C.Simple and inexpensive procedures for maintaining stock cultures of C. gracilis and for growth of cultures in the laboratory and hatchery were developed. A problem encountered in the hatchery tanks was the occasional development of a high-density bloom followed by its collapse. This resulted in mass larval mortality. Techniques to maintain the diatoms within desirable concentrations, and to prevent larval mortality if diatom concentrations fell short of or exceeded these limits, are described.