Study of zooplankton communities in shrimp earthen ponds, with and without organic nutrient-enriched substrates

Zooplankton communities were studied in shrimp ponds using different strategies to enhance natural productivity. The traditional treatment consisted of performing the strategy of simple fertilization (TT); for the alternative treatment (AT), fertilization was combined with the use of organic substrates enriched with nutrients; both treatments were stocked with shrimp post-larvae (Litopenaeus vannamei). Additionally, ponds with substrates but without shrimp were also studied (C). Total zooplankton concentration was greater in C ponds (1,002 org L-1) followed by AT (309 org L-1) and TT (124 org L-1), respectively. Copepods were the most abundant organisms in all treatments (a parts per thousand yen65 %), but their concentration decreased when shrimp were present in ponds. Such decline of copepods enhanced the proliferation of other zooplankton organisms such as polychaetes, protozoans, barnacles, ciliatea and others. Contents of shrimp stomachs exhibited a shrimp preference for copepods, polychaetes and protozoans; in addition, stomach contents of shrimp revealed their higher consumption of zooplankton when these organisms are abundant in the culture. Finally, shrimp reared in AT had a better growth performance than those from TT. It is concluded that enriched substrates are useful to improve and maintain high concentrations of zooplankton; copepods seem to suppress the proliferation of other zooplankton populations; however, they are preferred preys by shrimp.