Genetically Distinct Skipjack Tuna Subpopulations Appeared in the Central and the Western Pacific Ocean

Abstract

For better understanding of the Pacific-wide skipjack tuna Katsuwonus pelamis population structures, a series of genetic studies has been conducted. Analyses on genetic compositions of fish schools taken from the western Pacific Ocean and those from Hawaiian waters in different seasons together with tag-recovery data as well as size distribution in fish schools sampled made it possible to 1) break down the central-eastern Pacific subpopulations, defined before, into at least the three subpopulations genetically distinct each other: the central-west Pacific, the central-northeast Pacific, and the central-southeast Pacific subpopulations and to 2) delineate the range and the routes of migration of the central-west Pacific subpopulation. In addition, comparisons of the genetic data from Hawaiian waters and those from the other regions of the central Pacific and the eastern Pacific Ocean suggested necessity of further genetic work for more clear delineation of population structures as well as their migratory routes there. On the basis of the observations and the analyses conducted, a set of probable mechanisms of subpopulation differentiation was proposed to be considered for the sake of future works.