Abstract

The Yellowfin Tuna, Thunnus albacares, and the Blackfin Tuna, Thunnus atlanticus, are two tropical tunas commonly found in waters of the Gulf of Mexico and Caribbean Sea. Yellowfin Tunas are harvested by major commercial and recreational fisheries in both the East and West Atlantic. Blackfin Tuna occupy offshore waters of the west Atlantic where they are increasingly targeted by recreational fisheries and by commercial fisheries in the Caribbean region and South America. Information on stock structure is essential in order to develop sustainable management plans for these two important fish. In this work, robust panels of homologous microsatellite markers were developed and used to perform a first assessment of genetic stock structure of the two species in the Atlantic. After optimization and removal of error-prone markers, 14 and 13 polymorphic microsatellites were available to study population structure in the yellowfin and Blackfin Tuna respectively. To date, Yellowfin Tuna markers have been genotyped in a total of 752 samples collected over 3 sampling years from 3 regions in the West Atlantic and 2 regions in the East Atlantic. Divergence among samples was low (FST = 0.002) and no clear geographic pattern of population structure was evidenced. A total of 471 Blackfin Tunas from 7 regional populations were genotyped. Divergence among samples was also low (FST = 0.0008) and results to date suggest occurrence of a weak pattern of isolation by distance. Further study incorporating high density genome scans is in progress.

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