Diversity and abundance of epipelagic larvaceans and calanoid copepods in the eastern equatorial Indian Ocean during the spring inter-monsoon

Abstract

This study investigated the species composition, distribution and abundance of larvaceans and calanoid copepods in the eastern equatorial Indian Ocean. In total, 25 species of larvaceans and 69 species of calanoid copepods were identified in the study area. Although the average diversity and evenness indexes of larvaceans were lower than those of calanoid copepods, the abundance of larvaceans was higher than that of calanoids with means of 40.1±14.9 ind m^-3 and 28.4±9.1 ind m^-3, respectively. Larvacean community was numerically dominated by <i>Oikopleura fusiformis</i>, <i>Oikopleura longicauda</i>, <i>Oikopleura cophocerca</i>, <i>Fritillaria formica </i> and <i>Fritillaria pellucida</i>, accounting for 83% of total larvacean abundance. The calanoid community was dominated by the following five species, represented 61% of calanoid copepods: <i>Clausocalanus furcatus</i>, <i>Clausocalanus farrani</i>, <i>Acartia negligens</i>, <i>Acrocalanus longicornis </i> as well as the copepodite stage of <i>Euchaeta</i> spp. This study highlights that the importance of larvaceans in the eastern equatorial Indian Ocean.