Bluefin tuna conservation research in the central-southern Mediterranean spawning area

Abstract

Bluefin tuna (Thunnus thynnus thynnus) has been caught in the Maltese Islands since 1748. By 1995, when the Japanese bought bluefin tuna (BFT) caught by Maltese fishermen, the effort increased dramatically, however limited by the artisanal long-line gear used. Total BFT long-line fisheries landings have followed an over-all decline from a peak of 353,014kg in 1995 to 227,008kg in 2006. Close to 400 BFT specimens were sampled during six years to study variations in sizes, sex ratios, biogeographical characteristics and molecular genetics using microsatellite loci. This study's results indicate decreasing average BFT catch body size and an increasing sex bias for females. A significant genetic heterogeneity, FST value of 0.018 (P=0.015), was found among the BFT sampled in the spawning and fishing region south of the Maltese Islands.