Distribution of certain planktonic crustaceans and insect halobates in the Indian Ocean

Abstract

General distribution and numerical abundance of Cladocera, Ostracoda, Cirripedia, Mysidacea, Cumacea, Isopoda, Amphipoda, Euphausiacea, Stomatopoda and Insecta (Halobatidae) in the Indian Ocean are discussed. Areas of high overall zooplankton production coincide with areas of greater density of the above-mentioned groups. Western half of the Indian Ocean harbours a dense and steady population of almost all the groups except Cirripedia and Mysidacea which are fairly high in the Bay of Bengal. Ostracod population is very high in the Arabian Sea round the year and their peak abundance is always associated with high salinity waters in the Arabian Sea, Areas to the south of the sub-tropical gyre is poor in the case of almost all the groups mentioned above, but a gradual increase towards north can be found with a rich area in the north-west Indian Ocean. Day and night variations are pronounced in Ostracoda, Amphipoda and Euphausiacea. Studies on the distribution patterns with respect to the hydrographic features are also discussed.