Since zooplankton is the secondary producer of organic matter living on the phytoplankton in the marine food chain, its importance in fish production is self-evident (Rawson, 1956). It provides the essential food for many of the commercially important fishes such as juvenile and adult tunas (Reintjes and King, 1953), herrings, sardines, small fish, and economically important marine invertebrates like squid and shrimp (King and Hida, 1954; Hida and King, 1955). Aside from their role in the food chain, the zooplankton offer great possibilities as a source of protein for human consumption, directly or indirectly. For example, the euphau-siids, or “krill”, a highly pelagic crustacean that may still be regarded as zooplankton (Brinton, 1975), is now harvested and utilized as food of man. In Asia, animal plankton is used more as a food than it is in the western world. In Southeast Asia, fermented fish pastes are made from many kinds of sea animals, including planktonic crustaceans. Mainland Chinese eat a shrimp paste “as a main accessory food”. This paste is also eaten in India, Japan, and the Philippines.
This study is concerned primarily with the composition, distribution and seasonal variation in abundance of zooplankton in the Visayan Sea, particularly that of the planktonic crustaceans,, in relation to its hydrographical and meteorological conditions.