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Boundary between the north and south Atlantic populations of the swordfish (Xiphias gladius) inferred by a single nucleotide polymorphism at calmodulin gene intron
Chow, S.; Clarke, S.; Nakadate, M.; Okazaki, M. (2007). Boundary between the north and south Atlantic populations of the swordfish (Xiphias gladius) inferred by a single nucleotide polymorphism at calmodulin gene intron. Mar. Biol. (Berl.) 152(1): 87-93. hdl.handle.net/10.1007/s00227-007-0662-8
In: Marine Biology. Springer: Heidelberg; Berlin. ISSN 0025-3162, more
Peer reviewed article  

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Keyword
    Marine

Authors  Top 
  • Chow, S.
  • Clarke, S.
  • Nakadate, M.
  • Okazaki, M.

Abstract
    Genetic differentiation of the Atlantic swordfish (Xiphias gladius) was investigated by a single nucleotide polymorphism (SNP) at the calmodulin gene (CAM) intron locus. Clearly distinct allele and genotype frequencies were observed between the north (20–41°N) and mid-south (10°N–33°S) Atlantic samples. Much lower frequency of A allele (37.5–57.1%) was observed in the north samples (n = 160 in total) than in the mid-south samples (83.3–92.6%; n=354), and homozygote BB was common in the north samples (23.4–31.3%) but very rare or absent (0–3.9%) in the mid-south samples. Very strong population subdivision was observed between the two groups (F ST = 0.34, P < 0.001), while the allele and genotype frequencies within each ocean basin persisted over time (1990–2002 in the north, and 1994–2002 in the mid-south). Of two samples from the presumed boundary zone, one (n = 18) (14°N, 48°W) presented intermediate frequencies of the A allele (66.7%) and BB homozygote (11.1%), while the other (n = 23) (10–17°N, 28–37°W) shared similar frequencies of the A allele (89.1%) and BB homozygote (4.3%) with those of the mid-south Atlantic samples. These results indicate that the gene flow and individual migration between the north and mid-south Atlantic populations are considerably restricted and that the current management boundary between the north and south Atlantic swordfish stocks of 5°N should be reconsidered.

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