A preliminary report on the biomass of chaetognaths in the Indian Ocean comparing the south-west and north-east monsoon periods

Abstract

The data for the present paper have been derived from the analysis 1276 standard samples of plankton collected during the International Indian Ocean Expedition (1962-65) At the Indian Ocean Biological Centre fractions (3-5 ml) of the samples were sorted and the total number of chaetognaths in the samples were then computed The average number of chaetognaths for all samples from each 5 degrees Marsden Square is separately estimated for the south-west and north-east monsoon periods The period mid-April to mid-October (SW monsoon) shows a comparatively higher density of chaetognaths for all areas except the eastern half of the Arabian Sea In both the periods the areas of highest density are in the western part of the Arabian Sea The region 40 degrees -60 degrees E between the equator and the northern limit of the ocean is richest in Chaetognaths during both seasons