Zonation of chaetognath species along the south-west coast of India

Abstract

Zonation of chaetognaths in the pelagic realm was attempted by studying zooplankton samples collected along 3 sections off the south-west coast of India. Fifteen species were encountered in the samples. From inshore waters towards the offshore region species diversity increased from 8 to 14 per station in the oceanic region, even though abundance in terms of total number was more towards the inner shelf region. Concomitant with this, species composition also changed and based on the spatial preference shown by different species, 3 zoogeographic zones could be distinguished within the area under investigation: an inner shelf region of 6 species, an outer shelf region of 3 species and a slope region of 6 species. It is suggested that the prevailing environmental conditions resulted in characteristic association of chaetognath species. Effect of thermocline on the stratification of chaetognaths was studied. The results indicated that thermocline did not affect vertical disposition of most of the species.