The bigeye cigarfish (Cubiceps pauciradiatus) is a small pelagic nomeid of the tropical world ocean, often recovered in the stomach contents of top predators such as
tunas, billfishes and marine mammals. In the Indian Ocean, a few studies
have investigated the biology and the ecology of this species that is one of
the most abundant fish of the intermediate trophic levels. In this paper, we
investigated the spatial distribution of C. pauciradiatus in the Indian Ocean using pelagic trawl catches carried out between 20°N and 45°S, and the importance
of bigeye cigarfish in the diet of 9 piscivorous fishes sampled by different
fishing gears in the western part of the Indian Ocean. The highest densities
were observed along the eastern coast of Africa and in the Arabian Sea (87
000 individuals per square nautical mile) during the South-West Monsoon and
in the eastern part of the Seychelles archipelago (62 200 ind. square nmi)
during the North-East Monsoon. Small sized bigeye cigarfish (20–80 mm SL)
was a regular and abundant prey (20 to 200 ind. per stomach) for schooling
predators exploited by purse seine fishery such as large yellowfin and
bigeye tunas chasing prey near the sea surface. Large sized bigeye cigarfish
(61–150 mm SL) occurred in small numbers (3 to 20 ind. per stomach) in the
stomach contents of swordfish and of large yellowfin and bigeye tunas caught
by longline sets at great depths. Large concentrations of bigeye cigarfish
occurred in zones of high productivity, and that species constituted
seasonally a strong link in the transfer of energy from low to high trophic
levels in this part of the Indian Ocean.