Distribution and abundance of pelagic shrimps from the deep scattering layer of the eastern Arabian Sea

Abstract

The sonic scattering layer (SSL) or deep scattering layer (DSL) of the eastern Arabian Sea of India is found in depths between surfaces to 750 m with varying thicknesses and in multiple layers. There is a distinct resident community of pelagic shrimps that is widely distributed in the DSL biocomposition. Pelagic shrimps formed 19% of the total biomass and 47% of the micronekton biomass of the DSL. Many of them serve as important food resources to several pelagic/mesopelagic organisms. Pelagic shrimps concentrate in the deep scattering layer and diumally migrate in the water column. The estimated average abundance pelagic shrimps ranged between 0.04-106 /1000m sup(3). Shrimp catches were higher during night at 50-200 m depth than day. The dominant families encountered in the catches were Thalassocarididae, Pasiphaeidae, Sergestidae and Oplophoridae. Dominant genera of pelagic shrimps present were Gennadas, Sergestes, Sergio, Lucifer, Oplophorus, Acanthephyra, Nematocarcinus, Leptochela, and Thalassocaris. Species Sergestes seminuds, Thallassocaris crinata and Leptochela robusta were present in swarms