Observations on the plankton off Bombay coast with remarks on the hydrographic conditions and fishery

The study of fluctuations in plankton abundance in relation to hydrological features is of interest to planktonologists and fishery biologists. While there is relatively more information available on the hydrography of the waters off Bombay (Jayaraman and Gogate 1957 ; Carruthers et al. 1959 and Jayaraman et al. 1961), our knowledge of the plankton of this region is largely confined to the work of Bal and Pradhan (1945-47), Lele and Gae (1936), Gonzalves (1947) and Sudarsan (1964). The fish catches off Bombay are mostly composed of semidemersal species, predators on plankton feeding fish, crustaceans etc. The amount of plankton available may not have a direct and immediate effect on the fishery but it undoubtedly influences indirectly the fish abundance. The larvae, post-larvae and the juveniles of even the demersal fishes depend upon the planktonic organisms for their nourishment. As Bombay is one of the major fishing centres in the north-western part of India, the study of the hydro-biological features is very necessary as it might help understanding the effect of some of these parameters on the fisheries of the area. With this in view, investigations on the above aspects are being carried out at the Central Marine Fisheries Research Sub-Station, Bombay. The data collected so far on the abundance and fluctuations of plankton in relation to the observed hydrographical conditions of the fishing areas off Bombay are presented and discussed in this paper