After the amplification of the BDR region, PCR products were analysed by SSCP (Single Stranded Conformational Polymorphism) including amplicons obtained from DNA extracted from muscle from three different individuals of T. truncatus, from Thunnus alalunga plus amplicons from human DNA of two individuals involved in the analyses. The aim at this stage was to rule out the possibility of contamination. This analysis was done by an electrophoresis of PCR products in a vertical 6% polyacrilamide natural gel (Crosslink 75:1) at 15 Watts for 5 h. Denaturation during 5 min at 95°C in formamide loading buffer preceeded electrophoresis. SSCP patterns were visualised by Silver Staining following Hoelzel (1998).