Rythmes alimentaires et circadiens chez le germon thunnus alalunga (bonnaterre 1788)

During fishing campaigns for tuna on board the ship La Pélagia in 1968 and 1969 in the Atlantic, between the Gulf of Gascony, the southwest of Ireland and the Azores, the stomachs of caught tunny and those of tunny unsuitable for marking were sampled in order to study their contents at a later time. This study aimed to clarify certain problems relating to tunny feeding and we were able to highlight an endogenous diurnal rhythm in the white tuna's feeding, which is a new contribution to our knowledge about the biology of this fish. Currently, in fact, the problem of tuna feeding is still poorly understood; whereas the bibliography in this area is relatively rich, it is most often limited to lists of wildlife reports. In 1932 and 1940, R. LEGENDRE did an in-depth study of the Atlantic's pelagic fauna collected in the stomachs of tunny off the coasts of the Gulf of Gascony and, although this research is not centred on biological problems, it was a starting point for us, especially as regards species identification. In 1952, J.L. HUGH, then in 1962, R.T.B. IVERSEN studied tunny feeding and their stomach contents, according to various geographical, hourly or seasonal parameters, without however coming to any general conclusion about the nutritional rhythms of the white tuna. We have therefore attempted here to create a study centred not on wildlife issues, but on the contrary, oriented towards the study of the tunny's alimentary behaviour according to environmental criteria that can influence its biology. At the end of this work, we will discuss the few bits of information, still very fragmentary, that we have been able to collect on the listao (Katsuwonus pelamis).