Role of natural productivity in modified extensive shrimp pond growing <i>Penaeus monodon</i> (Penaeidae, Crustacea)

195-200Hydrobiology of a modified extensive shrimp (Penaeus monodon) culture pond was monitored. Qualitative and quantitative analyses of plankton population revealed higher phytoplankton population during the first six weeks of culture which declined to low level thereafter and remained at that level till the end of the culture period. Zooplankton was represented mainly by rotifers, copepods and mysids. Dense population of rotifers and copepods occurred during the first-month of culture while mysids appeared from the third week of first-month and dominated there after. Composition of zooplankton varied depending on the occurrence of Brachionus plicatilis, Keratella spp, Pseudodiaptomus annandalei Paracalanus aculetaus, Oithona brevicornis, Microstella norvegica and Mesopodopsis zeylanica during the culture period. Gut content analyses showed sand grains, zooplankton, pelletized feed and unidentified semi-digested food matter in the proportions of 43%, 16%, 21% and 20% respectively. The percentage of stomach contents varied in different size groups. It is observed that during the early phase of culture natural food contributes considerably to the growth of the shrimp