Observations on deep-sea benthopelagic nekton at two stations in the northern Arabian Sea: links to organic matter supply?

Benthopelagic nekton were sampled by trawl and baited trap arrays at two abyssal stations (WAST and CAST) in the northern Arabian Sea. The natantian decapod Plesiopenaeus armatus and fishes comprised most of the nekton caught by the trawls, whereas the amphipod Eurythenes gryllus dominated in the trap samples. At station WAST, Plesiopenaeus armatus made up 80% of the benthopelagic nekton in terms of biomass, fishes contributing 20%. This relationship was reversed at station CAST. The fishes caught belonged to 13 species in five families. Ophidiidae dominated in terms of abundance, followed by Synodontidae and Ipnopidae. Zoarcidae and Alepocephalidae were scarce, and no Macrouridae were caught. Synodontidae dominated in terms of biomass. Most fish were rather small, rarely exceeding a length of 40 cm. The amphipod Eurythenes gryllus was largely restricted to the traps lying directly at the bottom. A total of only five specimens were captured in pelagic traps from 8 to 500 m above bottom. The predominance of ophidiids and ipnopids, the small mean fish size, and the high standing stocks of natantian decapods suggest that the structure of the Arabian Sea benthopelagic nekton resembles that at abyssal depths in the tropical Atlantic and may be typical for the deep-sea at low latitudes.