Bacterial Degradation of Microencapsulated Foods Used in Larval Culture

Microencapsulated foods are widely used in the culture of larval fish, bivalves and crustaceans. The resistance to bacterial decay of two of these diets was investigated under microbial conditions similar to those found in hatchery cultures of larval penaeid prawndshrimps. A 2–3-fold increase in total ammonia concentration and a 7–14-fold increase in total bacterial numbers were detected within 48h when microcapsules were added to larval culture water at a density recommended by the manufacturer for one day of supplementary feeding. Increased dissolved total ammonia and bacterial populations were detected within 1.5h of addition of food to penaeid larval culture water. Scenning electron microscopy indicated that microcapsules were colonized by numerous bacterial cells within 1h. Physical disintegration of microcapsules occurred after 6 to 12h. Only in sterilized penaeid larval culture water did microcapsules remain intact for a significant period. These findings are discussed in relation to development of improved methods of larval culture.