Conservation Genetics

, Volume 8, Issue 6, pp 1355–1367 | Cite as

Stocking may increase mitochondrial DNA diversity but fails to halt the decline of endangered Atlantic salmon populations

  • K. L. Ciborowski
  • S. Consuegra
  • C. García de Leániz
  • J. Wang
  • M. A. Beaumont
  • W. C. Jordan
Research Article


Over the last 50 years, Spanish Atlantic salmon (Salmo salar) populations have been in decline. In order to bolster these populations, rivers were stocked with fish of northern European origin during the period 1974–1996, probably also introducing the furunculosis-inducing pathogen, Aeromonas salmonicida. Here we assess the relative importance of processes influencing mitochondrial (mt)DNA variability in these populations from 1948 to 2002. Genetic material collected over this period from four rivers in northern Spain (Cantabria) was used to detect variability at the mtDNA ND1 gene. Before stocking, a single haplotype was found at high frequency (0.980). Following stocking, haplotype diversity (h) increased in all rivers (mean h before stocking was 0.041, and 0.245 afterwards). These increases were due principally to the dramatic increase in frequency of a previously very low frequency haplotype, reported at higher frequencies in northern European populations proximate to those used to stock Cantabrian rivers. Genetic structuring increased after stocking: among-river differentiation was low before stocking (1950s/1960s ΦST = –0.00296–0.00284), increasing considerably at the height of stocking (1980s ΦST = 0.18932) and decreasing post-stocking (1990s/2002 ΦST = 0.04934–0.03852). Gene flow from stocked fish therefore seems to have had a substantial role in increasing mtDNA variability. Additionally, we found significant differentiation between individuals that had probably died from infectious disease and apparently healthy, angled fish, suggesting a possible role for pathogen-driven selection of mtDNA variation. Our results suggest that stocking with non-native fish may increase genetic diversity in the short term, but may not reverse population declines.


Salmo salar Stocking Mitochondrial DNA Conservation genetics Foreign gene introgression 


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Copyright information

© Springer Science+Business Media, Inc. 2007

Authors and Affiliations

  • K. L. Ciborowski
    • 1
  • S. Consuegra
    • 2
  • C. García de Leániz
    • 2
  • J. Wang
    • 1
  • M. A. Beaumont
    • 3
  • W. C. Jordan
    • 1
  1. 1.Institute of Zoology, Zoological Society of LondonLondonUK
  2. 2.School of Biological Sciences, University of Wales SwanseaSwanseaUK
  3. 3.School of Animal and Microbial Sciences, University of ReadingReadingUK

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