Genetic and morphological identification of larval and small juvenile tunas (Pisces: Scombridae) caught by a mid-water trawl in the western Pacific
2003
Chow, S. (National Research Inst. of Far Seas Fisheries, Shimizu, Shizuoka (Japan)) | Nohara, K. | Tanabe, T. | Itoh, T. | Tsuji, S. | Nishikawa, Y. | Uyeyanagi, S. | Uchikawa, K.
Abstract Diagnostic DNA markers based on the restriction fragment length polymorphism (RFLP) and nucleotide sequence analyses on two regions of the mitochondrial DNA (cytochrome b gene and flanking region between ATPase and CO3 genes) were obtained using representative specimens of Auxis rochei, A. thazard, Euthynnus affinis, Katsuwonus pelamis, Sarda orientalis and all Thunnus species. These DNA markers were applied to a total of 936 scombrid larvae and juveniles ( 9 mm to 186mm in standard or fork length) collected by a mid-water trawl operated in the tropical and sub-tropical western Pacific during 1992 to 1998. Four Thunnini species (K. pelamis, T. alalunga, T. albacares, and T. obesus) were observed in the samples from the open water area (2deg N-15deg N, 135deg E-157deg E), while eight species (A. rochei, A. thazard, E. affinis, K. pelamis, S. orientalis, T. alalunga, T. albacares and T. thyanus orientalis) were observed in the samples from the island associated area (24deg N-30deg N, 123deg E-131deg E). Gill rakers were not fully developed in the juveniles smaller than 60mm in fork length, and may not be useful for identifying the species of Thunnus and Auxis.
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