Analyse démographique des captures de thon rouge et de la thonine des madragues tunisiennes

Abstract

The temporal evolution of the demographic structure of bluefin tuna (Thunnus thynnus, Linnaeus 1758) and of the little tuna (Euthynnus alletteratus, Rafinesque 1810) by the Tunisian traps of Sidi Daoud and Monastir is studied during 3 periods (1979-1983; 1988-1992 and 1993-1997). This survey showed the two points of passive capture landing draw the bluefin tuna from two populations of different composition. Fishes took in the Tunisian waters don't form a similar being grouping. Does it value the variation can be to a mixture of local, Mediterranean and Atlantic shape. A conclusion to which arrived Heldt (1929), confirmed in 2004, by studies of tagging bluefin displacements tagged in Mediterranean with satellite Pop up tag by satellite during 1998-2000 that indicated that adults (<100 kg) stay in the Mediterranean after reproduction and that after the spawning, the giant bluefin tuna migrate in the Atlantic northeast. , For the little tuna, the two traps harvest one same Mediterranean stock, even though the genetic studies on the little tuna according to the sequential data on mitochondrial DNA revealed an important degree of differentiation of certain s populations suggesting that movements of these fishes are compelled to the limited areas.