Determination of application dosages of a commercial nutrient powder to induce growth of zooplankton as feed for white leg shrimp (Litopenaeus vannamei) in intensive culture ponds

Abstract

This study was conducted to determine the most suitable dosage of a commercial nutrient powder (as a kind of fertilizer) for inducing zooplankton growth to be initial feed for newly stocked postlarvae (PL) of white leg shrimp in intensive culture ponds. The experiment wasconducted in 9 earthen ponds with area of 2,000 - 2,500 m2. Three different dosages of nutrient powder were applied, standing for three treatments including (i) 1kg/100.000PL (T1); (ii) 0.5kg/100.000PL (T2); and (iii) 1.5kg/100.000PL (T3). Each treatment consisted of 3 ponds (3 replicates). The powder was applied 2 days before stocking and every day starting from stocking to day 10. Zooplankton was sampled daily both qualitatively and quantitatively. Shrimps were also collected every day for growth and intestine feed analysis. Some water parameters such as TN, TP were also monitored every three days. The result showed that total number of zooplankton species found was low with only 13 species. There was no significant difference in species number between treatments. Copepods were the major group accounting for a high proportion in the fauna. Zooplankton densities in T1 and T2 were quite high (7,200,931 inds/m3) during the first 9 days; in contrast, zooplankton density in T3 zooplankton was much lower (132,528 inds/m3). Copepods and Rotifers were the main groups of zooplankton in the digestive system of shrimps. However, copepod nauplii and rotifer were the most important live food items due to their high proportions in the digestive system of shrimps and the choice of shrimps for these items as food.