Distribution of mesopelagic micronekton in the Arabian Sea during the winter monsoon

Abstract

Response of micronekton to oxygen minimum zones in the Arabian Sea (AS) during winter monsoon period was investigated using data of 52 trawls deployed during four winter cruises between 1998 and 2000. Twenty-nine species, representing 19 groups were identified in the deep scattering layer (DSL). The mesopelagic community was dominated by shrimps, myctophids, fish larvae, phosichthyids and leptocephalus. Based on the distribution, two regions were distinguished: the southern Arabian Sea (sAS) and the northern Arabian Sea (nAS). Ceratoscopelus warmingii, Diogenichthys panurgus, Diaphus fragilis, Lampanyctus turneri, Thallasocaris carinata, Leptochela robusta, Oplophorus typus, Viniciguria nimbaria, V.leucita were dominant in the sAS; Benthosema pterotum, Bolinichthys longipes, Diogenichthys panurgus, D. fragilis, D. aliciae, V. nimbaria, V. leucita were dominant in the nAS. Most of these species were abundant in the upper 50 m during night, but were found in the oxygen minimum zone (OMZ) between 175 to 800 m north of 13oN during daytime. Fourteen of 29 species were detected within the OMZ during day time.