The abundance of zooplankton in marine environment has direct influence on fishery resources and it is influenced by environmental parameters such as circulatory movements (eddies) and vertical turbulent mixing. The important role of plankton including both microzooplankton and macrozooplankton in supporting life in the sea was recognized in the past, but the study related to ecology of these organisms has still recently formed as intractable aspect in marine ecosystem.  Life in the sea has been broadly classified into three groups, viz., the plankton, the nekton and the benthos. The majority of the faunal assemblages of the plankton consists of zooplankton. Among the various levels of production in the sea the secondary production, i.e., production of zooplankton, attains significance as it serves as a link between primary production and tertiary production. The zooplankton chiefly consumes the primary producers and forms the major food source for tertiary producers. Zooplankton plays an important role in coral reef ecosystem. They serve as food for corals, and a variety of other invertebrates and reef fishes. From the fishery point of view, zooplankton forms food of/ from important batfishes belonging to the families Clupeidae, Caesionidae and Apogonidae. Some fishes are exclusively zooplankton feeders and therefore their abundance is directly linked to the presence of zooplankton.