Modeling the effect of nitrogen input from feed on the nitrogen dynamics in an enclosed intensive culture pond of black tiger shrimp (Penaeus monodon)

In the present study, a mathematical model was developed to evaluate the effect of nitrogen (N) input from feed on the N dynamics under different feeding scenarios in a well aerated and enclosed culture pond of black tiger shrimp (Penaeus mon- odon). Three feeding levels were examined: underfeeding, optimum feeding and overfeeding. The model was formulated using field data gathered from an earthen pond (0.69 ha) which was stocked with shrimp post larvae at a density of 340,000 individu- als ha �1 and grown for 151 d. The model suggested that the underfeeding rate (329 kg N ha �1 cycle �1 ) observed from the study pond, which was being underfed, resulted in the ingestion of the natural productivity in the pond. With the underfeeding prac- tice, phytoplankton assimilated ammonia and nitratenitrite at the rates of 412 and 52 kg N ha �1 cycle �1 , respectively, while ni- trification rate in the water column was 45 kg N ha �1 cycle �1 . The coupled processes of nitrification and denitrification in sedi-