Temporal changes in allele frequencies but stable genetic diversity over the past 40 years in the Irish Sea population of thornback ray, Raja clavata

M. Chevolot, J.R. Ellis, A.D. Rijnsdorp, W.T. Stam, J.L. Olsen

Research output: Contribution to journalArticleAcademicpeer-review

24 Citations (Scopus)

Abstract

Rays and skates are an unavoidable part of the by-catch in demersal fisheries. Over the past 40 years, the thornback ray (Raja clavata) has decreased in numbers and even disappeared in some areas, leading to concerns about genetic risk. For this reason, the effective population size (Ne), the migration rate (m) and temporal changes in the genetic diversity were estimated for the population of thornback rays in the Irish Sea and Bristol Channel. Using genotyped, archived and contemporary samples (1965 and 2003¿2004), Ne was estimated at 283 individuals (95% CI=145¿857), m at 0.1 (95% CI=0.03¿0.25) and the Ne/N ratio between 9 10¿5 and 6 10-4. Although these results must be treated with caution, due to the small sample sizes, this is the first attempt to estimate Ne in an elasmobranch species. The low Ne/N ratio suggests that relatively few individuals contribute to the next generation. The combined effect of sex bias, inbreeding, fluctuations in population size and, perhaps most important, the variance in reproductive success may explain the low Ne/N ratio. In addition, the relatively high gene flow between Irish Sea population and other source populations is likely to have had an impact on our estimate, which may be more relevant at the metapopulation scale. No significant loss of genetic diversity was found over the 40-year timeframe and long-term maintenance of the genetic diversity could be due to gene flow
Original languageEnglish
Pages (from-to)120-126
JournalHeredity
Volume101
DOIs
Publication statusPublished - 2008

Keywords

  • adult census size
  • cod gadus-morhua
  • north-sea
  • overlapping generations
  • reproductive success
  • mating-behavior
  • british waters
  • large variance
  • marine fish
  • dna

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