Spatial distribution of Cubiceps pauciradiatus (Perciformes: Nomeidae) in the tropical Indian Ocean and its importance in the diet of large pelagic fishes

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. Ce poisson pélagique, Cubiceps pauciradiatus, à répartition circum-tropicale, est fréquemment observé dans les contenus stomacaux des grands prédateurs tels les thons, les poissons à rostre et les mammifères marins. Dans l'océan Indien, très peu d'études ont été menées sur la biologie et l'écologie de cette espèce qui est l'une des plus abondantes des niveaux trophiques intermédiaires. Dans cet article, nous décrivons, à partir des résultats de chalutages pélagiques réalisés entre 20°N et 45°S, la répartition géographique de C. pauciradiatus dans l'océan Indien et son rôle dans l'alimentation de 9 grands prédateurs capturés à la senne et à la palangre dans l'ouest de l'océan Indien. En mousson de sud-ouest, les plus fortes densités sont observées le long de la côte est-africaine et en mer d'Arabie (87 000 par mille2 de surface), et en mousson de