Abstract for presentation at 11th International Congress of Human Genetics

Tuna are the major marine fishery in Sri Lanka and Skipjack Tuna (SJT) and Yellow Fin Tuna (YFT) form the most important component species with the Tuna catch increasing rapidly each year in Sri Lanka and generally in the Indian ocean. To date however, no genetic studies have been done to assess wild stock structure in Sri Lankan waters for management purposes. The current study is the first to document the extent of wild Tuna genetic resources in Sri Lanka.
Samples of both SJT and YFT were collected over a period of 4 years from 9 major fishing grounds around Sri Lanka in the Indian ocean referred to as West, Southwest, South, Southeast, East, Northeast, Northwest and also from the Maldive and Laccadive islands. Sample locality (GPS), body length and sex data were recorded.
mtDNA and nDNA variation was examined for ~350 individuals of each species to document genetic diversity within and among sampled sites and hence to determine stock structure and to infer migratory behaviour for both species. ATPase-COIII region sequences of the mitochondrial genome were amplified and genetic variation determined using TGGE (Temperature Gradient Gel Electrophoresis). Haplotypes were determined from banding patterns and each unique haplotype was sequenced. Microsatellite markers were developed for both species via DNA cloning and nDNA variation was examined for each species at 3 Tetra- and Tri-nucleotide microsatellite loci.
40 and 16 unique mtDNA haplotypes were found in SJT and YFT samples, respectively. Analyses of mitochondrial ATPase-COIII region sequences and microsatellite genotypes revealed significant genetic variation in SJT among all sites. Some significant differentiation was also observed among sites in the more pelagic YFT and this will be discussed.