Lack of congruence between genetic and morphological stock structure of the southern African anglerfishLophius vomerinus

Abstract

Meristic and morphometric variation and isozyme population markers were used to study the geographic stock structure of the southern African anglerfish Lophius vomerinus. Analysis of variance (ANOVA) revealed that the numbers of vertebrae and left pectoral fin rays differed significantly among areas. ANOVA of size-free estimates of morphometric variables showed that the length of the second dorsal fin spine, the head width and the snout width differed significantly among areas. A size-free principal component analysis (PCA) revealed that head characters and dorsal spine lengths covaried. A discriminant function based on meristic and morphometric characters correctly classified 36 and 51 per cent of the individuals respectively. A total of 24 protein-encoding loci was examined for Mendelian variation with starch-gel electrophoresis. Average heterozygosity (H) was 12,6 per cent, larger than that for most other marine fishes. There were no significant differences in allele-frequency among areas for nine polymorphic loci. A gene-diversity analysis showed that most of the genetic variation was contained within areas (99,62%), and that only a fraction of the total (0,38%) could be attributable to geographic differences among locations. Combining the data shows that the slight morphological differentiation among areas does not have a genetic basis. A conservative management policy, however, would be to set separate harvesting quotas for Namibia, for the South African west coast and for the South African south coast.