ICES Journal of Marine Science: Journal du Conseil Advance Access originally published online on April 29, 2009
ICES Journal of Marine Science: Journal du Conseil 2009 66(5):816-825; doi:10.1093/icesjms/fsp120
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Microsatellite and mitochondrial haplotype differentiation in blue mackerel (Scomber australasicus) from the western North Pacific
1 Department of Life Science, Institute of Zoology, National Taiwan University, Taipei 10617, Taiwan
2 Institute of Marine Affairs and Resource Management, National Taiwan Ocean University, Keelung 20224, Taiwan
Correspondence to T-S. Chiu: tel: +886 2 33662448; fax: +886 2 23634014; e-mail: tschiu{at}ntu.edu.tw.
Tzeng, C-H., Chen, C-S., Tang, P-C., and Chiu, T-S. 2009. Microsatellite and mitochondrial haplotype differentiation in blue mackerel (Scomber australasicus) from the western North Pacific. – ICES Journal of Marine Science, 66: 816–825.Blue (Scomber australasicus) and chub mackerel (Scomber japonicus) occur sympatrically in the western North Pacific. Blue mackerel were previously classified as a subspecies of S. japonicus based on morphological similarities. The practical management unit for blue mackerel is contentious owing to incomplete resolution by biological analyses. We used rapidly evolving microsatellites and slow-changing mitochondrial cytochrome b (mtCyt-b) markers to examine the phylogeographic relationships of the two species across four major hydrographic regions of the western North Pacific. Genetic variability was high in each hydrographic region and in the putative species unit, and Hardy–Weinberg equilibrium tests confirmed that blue and chub mackerel are separate genetic components. Population genetic and multiple-dimensional scaling analyses of the genotypes indicated clear genetic differences, and phylogenetic analyses of the mtCyt-b haplotypes showed a level of genetic divergence (FST = 0.038, p < 0.001) consistent with separation of the two species. Based on the coalescence theory, the difference in mtCyt-b genes was small, indicating incipient speciation between blue and chub mackerel, with a diversification time of 1.9 million years ago (mya) during the Pleistocene when the East China Sea (ECS) and the South China Sea (SCS) were separated physically. Significant differences between populations of blue mackerel in the ECS and SCS were also found. Our findings confirm that blue mackerel is a valid biological species and that its populations in the ECS and SCS should be considered separate fishery stocks and conservation units for management.
Keywords: microsatellite, mitochondrial cytochrome b, Scomber australasicus, S. japonicus, species, stock
Received 11 November 2008; accepted 31 March 2009; advance access publication 29 April 2009.