Zooplankton exhibit diel vertical migration (DVM) in which,  the hours of darkness are spent near the surface and the day light hours at deeper depths. DVM, though studied by many workers, is poorly understood. Hence an attempt has been made to study and understand DVM pattern in Andaman Sea, known not only for its oligotrophic nature, but also for low primary and secondary productivity. The zooplankton samples were collected from the upper most euphotic zone for 24 hrs at an interval of two hours by using a Bongo net. The biomass and wet weight varied from 0.01 - 0.05 ml m^-3 and 0.4-2.2 mg m^-3 respectively. Copepods dominated the samples, followed by chaetognaths, amphipods, siphonophores, crustaceans and pelagic tunicates. The present studies reveal that, not only the light intensity, but also the feeding habits, reproductive stage and age of organism alters DVM in zooplankton.

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