Inter-annual variations of selectedoceanographic parameters and itsrelation to fishery of small pelagicsoff Kochi, southwest coast of India

Abstract

The availability as well as abundance of selected small pelagics along Kerala coast (south west coast of India) was highly variable during the past three decades. During the period 1980-2012 there have been several periods of abundance as well as population crashes in the oil sardine fishery. The present study revealed that the occurrence of low sea level during the month of May implies either early wind driven upwelling or early intensification of equator-ward coastal current and consequent upsloping of isopycnals. The occurrence of low sea level (6857) as early as in May and upwelled water in August with low dissolved oxygen (0.68 ml l-1) with low sea water temperature (24˚C) at the bottom at 10 m depth, off Kochi was found to affect the sardine fishery in the year 1994, when the landing at Kochi was only 15 t. Mean sea level was found to be a sign of upwelling and the real time observations of dissolved oxygen indicated wide variations during the upwelling period.