Journal of the Marine Biological Association of India

Distribution of some oceanographic factors in the Arabian Sea Off Manjeswar and their possible effect on oilsardine and mackerel fisheries in the area.

Volume 33 Issue 1&2

T. V. Ramana, D. E. Nathaniel and M. P. M. Reddy

Abstract

Studies on the vertical and monthly distribution of sea water temperature, salinity, dissolved oxygen and some other oceanographic parameters carried out at eight stations in the Arabian Sea off the Manjeswar revealed some interesting features. Generally, the waters off Manjeswar within 50 m depth were found to be more or less isothermal during January, February and December. In May, September and October, vertical temperature gradients in the 50 m depth water column were comparatively high. The studies indicated the presence of the top of the thermocline between 10 and 15m depths during September. The increase of salinity with depth was more pronounced during the period from March to November probably due to the occurrence of salinity stratification in these months. Near isohaline conditions were present together with a deep thermal mixed layer during January, February and December perhaps due to the mixing associated with strong winds.

Of all the important oceanographic parameters, water temperature and salinity of columnar waters appeared to have direct effect on the pelagic fisheries of oil sardine and mackerel in the area. Any deviation from their respective optimum values of columnar water temperature and salinity appeared to be responsible for the low catches of oil sardine and mackerel. Rainfall, pH, dissolved oxygen and transparency were found to have indirect effect on the pelagic fishery of oil sardine and mackerel.

Date : 31-12-1991