Bayesian analysis of allozyme markers indicates a single genetic population of kingklip Genypterus capensis off South Africa

  • WS Grant Marine Biology Research Institute, University of Cape Town, Private Bag, Rondebosch 7701, South Africa; current address: Department of Biological Sciences, University of Alaska Anchorage, Anchorage, AK 99508, USA
  • RW Leslie Marine and Coastal Management, Department of Environmental Affairs and Tourism, Private Bag X2, Rogge Bay 8012, South Africa
Keywords: allozymes, <i>Genypterus capensis</i>, marine fish, population genetics, southern Africa

Abstract

Kingklip Genypterus capensis inhabit deep continental shelf and slope waters off southern Africa and are now largely harvested as a bycatch in trawl and longline fisheries for Cape hakes Merluccius spp. Regional differences in growth, vertebral count and otolith morphology indicate that kingklip may consist of three stocks. In this study, allozyme markers are used to test whether the two southern stocks, the putative Cape and South Coast stocks, are genetically distinguishable. Standard electrophoretic methods detected Mendelian polymorphisms at six (23%) of 26 enzyme-encoding loci in five samples extending from about 29°S on the West Coast to about 25°E on the South Coast. No deviations from Hardy-Weinberg proportions were observed in the samples or in the pooled sample. Gene diversities (heterozygosity) ranged from HS = 0.039 to 0.042 among samples, and averaged 0.041. Genetic differentiation among localities was remarkably small, FST = 0.003, and did not differ significantly from zero. A Bayesian analysis of population structure, based on detecting departures from Hardy-Weinberg proportions and gametic phase equilibria between loci, indicated with a high likelihood that the five samples were drawn from a single genetic population. In combination, these results are consistent with the occurrence of a single population off South Africa. However, the most conservative management strategy is to set harvest quotas individually on the Cape and South Coast stocks.

Keywords: allozymes; Genypterus capensis; marine fish; population genetics; southern Africa

African Journal of Marine Science 2005, 27(2): 479–485
Published
2005-11-04
Section
Articles

Journal Identifiers


eISSN: 1814-2338
print ISSN: 1814-232X