Global population structure of yellowfin tuna, Thunnus albacares, inferred from allozyme and mitochondrial DNA variation

Abstract

566 Abstract.-Yellowfin tuna, Thun­ nus albacares, were sampled from one region of the Atlantic Ocean. two re­ gions of the Indian Ocean, and six re­ gions of the Pacific Ocean. One of the Indian Ocean collections could not be allozymically analyzed; the remaining eight collections were examined for four polymorphic allozyme loci , with two restriction enzymes lBel I and Eco RI) that detect polymorphic restric­ tion sites in yellowfin tuna. Allele fre­ quencies at three of the allozyme loci were homogeneous across collections, whereas GPI-A* showed highly signifi­ cant differentiation (P<O.OOI). The GPI-A* data, taken together with the geographic location of the collections, suggested the existence ofat least four yellowfin tuna stocks: Atlantic Ocean, Indian Ocean, west-central Pacific Ocean, and east Pacific Ocean. Mito­ chondrial DNA differentiation was more limited, but spatial heterogene­ ity of the 24 observed haplotypes over the nine regions (P=O.048l and three oceans lP=O.009) was significant. The mtDNA data did not differentiate west­ central Pacific Ocean collections from east Pacific Ocean collections but did support the separation of Atlantic Ocean, Indian Ocean. and Pacific Ocean stocks.