The mesopelagic fauna of the western and northern Arabian Sea between Mogadisco and the Indo-Pakistanean border was studied with R/V “Dr. Fridtjof Nansen” during 1975-1976.
A DSL laying in depths between about 250 and 350 m was found in the whole area. In the north-western part of the area and sometimes in the Gulf of Aden, an additional layer was found between about 100 and 200 m.
Benthosema pterotum and B. fibulatum were the most abundant species in the area but Diaphus spp. were also numerous. The Benthosema species seem to have a life cycle of one year or less.
The biomass was estimated using a 38 kHz echo sounder and electronic integration technique. The area was covered five times and the estimated abundance of mesopelagic fish was 102 million tons (range 56-148 million tons). Estimates from the spring were higher than those from summer and autumn.
With a 1360 mesh pelagic trawl catch rates as high as 20 tonnes/hour of trawling were reached.
