Genetic structure of swordfish (Xiphias gladius) populations of the Mediterranean and the Eastern side of the Atlantic: Analysis by mitochondrial DNA markers <B>Genetic structure of swordfish (Xiphias gladius) populations of the Mediterranean and the Eastern side of the Atlantic: Analysis by mitochondrial DNA markers</B><P> </B><I></I><B>Magoulas A., G. Kotoulas N. Tsimenides and E. Zouros</B><I><BR> Institute of Marine Biology of Crete, P.O. Box 2214, 71003 Iraklion, Crete, Greece & University of Crete, Biology Department, P.O. Box 1470, 71110 Iraklion, Crete, Greece</I><B><P> J. M. de la Serna</B><I><BR> Centro Oceanografico de Fuengirola, Fuengirola, Spain</I><B><P> G. de Metrio</B><I><BR> University of Bari, Department of Animal production, Bari, Italy</I><B><P> Summary</B><BR> Restriction site polymorphism of mitochondrial DNA (mtDNA) was score in three<BR> samples of swordfish (<I>Xiphias gladius</I>) from the Mediterranean and in two samples from the eastern Atlantic Ocean. Using two restriction endonuclei (<I>Pv</I>uII, <I>Eco</I>RV), four composite restriction patterns (genotypes) were revealed. All four genotypes were present in both seas but in different frequencies. The three Mediterranean samples (Greece, Italy, Spain) did not differ significantly from each other in their genotypic frequencies. There was, however, a very significant difference between the two Atlantic samples. The samples from Tarifa (just off the Strait of Gibraltar) did not differ from the Mediterranean samples, but the sample from the Gulf of Guinea differed greatly from all other samples (Mediterranean and Tarifa). These observations suggest the existence of one homogeneous stock in the Mediterranean different from that found in the eastern tropical Atlantic. The similarity of the sample from Tarifa with those from the Mediterranean is consistent with the view that the Strait of Gibraltar does not restrict the movement of swordfish between the Atlantic and the Mediterranean.<P> Reference: Second GFCM/ ICCAT Expert Consultation on Stocks of Large Pelagic Fishes in the Mediterranean Sea (Iraklion, Crete, Greece, September 17-23, 1992). INternational Commission for the Conservation of Atlantic Tunas. Collective Volume of Scientific Papers Vol XL (1). ICCAT, Principe de Vergara, 17-7, 28001, Madrid, Espana. Madrid, VI-1993<P>