Population Structure Study of Swordfish Xiphias gladius in the Pacific Ocean Inferred by Genetic Informative Data Differentiation Using High Resolution Melting Analysis (HRMA)

There is no consensus on the population structure of swordfish in the Pacific Ocean.  In an attempt to clarify this structure, genetic analyses were carried on representative samples from six regions: Southwest Pacific (Eastern Australia, n=40), Southeast Pacific (Chile, n=155), Eastern-Central Pacific (Ecuador, n=40), Northeast Pacific (Mexico-Temperate, n=40), Central Pacific (Central-Equator, n=31) and Northwest Pacific (Taiwan, n=64).  Genetic variation was characterized for eight nuclear genes using High Resolution Melting Analysis (HRMA) and length polymorphisms.  Preliminary results of multiple locus analyses reject the null hypothesis of panmixia for Pacific Swordfish.  No significant difference was found among South Pacific samples (Eastern Australia, Chile, and Ecuador). However, highly significant differences were found between each of the South Pacific samples against each of the North Pacific Samples (Mexico-Temperate, Central-Equator, and Taiwan).  In the North Pacific Ocean, a highly significant difference was found between Northwest Pacific (Taiwan) and Northeast Pacific (Mexico-Temperate). Larger sample sizes are needed to provide statistical power to these tests.