The relative contribution of natural productivity and formulated food in the nutrition of Penaeus japonicus reared in semi-intensive conditions

The relative contribution of natural productivity and of artificial diet in the nutrition of Penaeus japonicus reared in semi intensive pond aquaculture was studied in the Island of Noirmoutier (Atlantic coast of France) using two complementary methods: the isotopic labelling of carbon (stable isotopes) and chromic oxide. The first method gave an estimation of the cumulated contribution of both foods and the assay of chromium in the feces of shrimps caught in the pond and kept in tanks allowed an estimation of the intake of compound food. With the combination of both methods, it was shown that compound diet fed from the stocking time plays but a limited role during the first weeks, but its contribution increases later untill becoming essential. On the other hand, the distribution of compound food has a constant positive influence on the "natural" productivity of the pond. Its participation to overall productivity may reach 30% of total biomass.