The commercial fisheries for penaeid prawns of the southwest coast of India are supported by several species that often oocur simultaneously. It is a known fact that these prawns -breed in the sea and their planktonic larvae enter the estuaries and backwaters as they transform into late my.is or postlarval stages. The establishment of the correct identity of the postlarval forms of each of the constituents of this multispecies fishery is essential in order to understand the dyna~ics of the juvenile and adult populations. This is particularly so, when the juveniles as well as adults are subjected to commercial exploitation. Differentiation of these developinB stages into their respective species has been rendered difficult owing to their apparent similarities in shape, size and habits.