Abstract

Blackfin tuna, Thunnus atlanticus (Lesson, 1831), is a highly migratory neritic species of tuna restricted to the tropical epipelagic waters of the western Atlantic, from Martha’s Vineyard off the coast of the U.S. (40oN) to 31oS off the coast of Brazil. Blackfin tuna is targeted by recreational fisheries throughout its range, and also by small artisanal fisheries throughout the Caribbean and off the northern coast of Brazil. Catch data reveals a slow but steady increase in commercial catches over the past 25 years. In spite of this increase in fishing pressure, there is no information available on the patterns of genetic variability of blackfin tuna, and with that purpose we characterized the nucleotide sequence variation contained in the mitochondrial DNA (mtDNA) control region (CR) and in the nuclear genome using a battery of seven microsatellite loci. These data were used to reconstruct the historical demographic and phylogenetic signals of this species, and to estimate effective population sizes. We present preliminary data that reveals surprisingly high levels of genetic variation in blackfin tuna. We are currently examining this data to test the null hypothesis of no differentiation among samples from the Gulf of Mexico, Bermuda, and off the coast of South Carolina. This information is aimed to serve as baseline data to aid in the fishery management of this species.

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