Subtidal benthic macrofauna of the Mangalore coast, west coast of India

Subtidal macrobenthic fauna from the Mangalore coast was studied from the s helf areas between the old Mangalore Port and Suratkal, covering an area of approximately 40 km(2). Benthic bivalves were the most abundant group, (36 160/m(2)) in December. During the same period, gastropods which also coexis ted, showed their highest density (6400/m(2)), followed by a lean period up to April. Peak abundance of polychaetes was during May (3380/m(2)) with co nsequent reduction during the time of bivalve dominance and vice versa. Oth er groups recorded occasionally were amphipods, heteropods, holothurians, j uvenile star fishes, stomatopods, cephalochordates, sipunculids, oligochaet es, cumaceans and decapods. The area between the old Mangalore Port and New Mangalore Port appeared to be more productive compared to the suratkal are a in the north. The striking difference noticed was the shift in the benthi c production from the 5 m contour. In all the earlier works 5 m contour lin e was found to be most productive, with a decrease in biomass with depth. I n the present observations 5m contour line was least productive with an inc reasing trend up to 20 m, both in biomass and numerical density.