SCHOOLS OF LARGE YELLOWFIN (Thunnus albacares) CONCENTRATED BY FORAGING ON A MONOSPECIFIC LAYER OF Cubiceps pauciradiatus, OBSERVED IN THE EASTERN TROPICAL ATLANTIC

Abstract

SUMMARY Observations on stomach content of large yellowfin tuna were carried out aboard a purse seiner operating in EasternTtropical Atlantic during early 2001.A monospecific concentration odf large yellowfin was observed during several days. These large fish were feeding on a monospecific concentration of Cubiceps pauciradiatus. These small fish were juveniles agregated in a thick layerat moderate depth and stable by day and night, feeding on zooplancton. This simple food web induce a concentration of large yellowfin tuna in the Equatorial area,and it seems that such situation occur rather frequently. However the relation of this feeding behaviour with spawning activity whichis known to occur in the same time area strata has still to be explored. Many thanks to Bernard SERET for precise zoological determination of Cubiceps pauciradiatus based on specimens collected in stomach contents of yellowfin. Many thanks as well to the crew of the purse seiner VIA HARMATTAN . RESUME