Biochemical genetic stock structure of the southern African anchovy, Engraulis capensis Gilchrist

The geographical distributions of inherited biochemical markers were used to measure the amount of genetic isolation between stocks of Namibian and South African anchovy, Engraulis capensis . A contingency-table analysis of allele frequencies for 10 polymorphic protein-coding loci revealed no significant frequency differences between spawning areas. The average Nei genetic distance between samples was 0.0003 and there were no geographic trends in the amount of genetic distance between populations. Average population heterozygosity for 31 loci was 0.115 and this accounted for 99.26% of the total genetic variation. The remaining 0.24% was due to all temporal and spatial differences combined. The observed amount of genetic divergence between populations was used to estimate the amount of migration between spawning areas, using the stepping-stone model of migration. As few as 13 migrants may account for the observed genetic divergence between spawning areas. The validity of using the genetic stock concept in the management of marine fishes is discussed.