The stocking density was 20 individuals/m2, lower than the 50/m2 specified for shrimp aquaculture on an intensive scale (Mena-Herrera et al., 2006), but similar to commercial farms working on a semi-intensive scale, where the enhancement of natural productivity before and during culture is possible. In addition and also similar to commercial farms, artificial feed was not limited. Shrimp in the enhanced ponds showed a marked preference for natural food. In the unenriched ponds, natural food was observed in the stomachs of all shrimp whereas not all stomachs contained artificial feed. The preference for natural food could indicate that artificial feed can be reduced if natural productivity is enhanced. The stomach contents indices suggest that high densities of natural food enhance the feeding activity of shrimp. A higher proportion of full stomachs and lower proportion of empty ones were observed in shrimp from the enhanced ponds where natural food was abundant. “At some point” in the growth process of white shrimp, a change in feeding preference can occur, during which growth is supported mainly by nutrients from natural productivity (Gamboa-Delgado et al., 2003). The higher amount of empty stomachs in shrimp from unenhanced ponds could be associated with the lower natural productivity and a change in feeding preference.
The frequencies of each type of prey in the stomachs