Genetic analyses of overfished silver kob Argyrosomus inodorus (Scieanidae) stocks along the southern African coast

• Population genetic analyses were carried out on silver kob stocks.
• Overfished South African stocks showed signatures of genetic bottleneck.
• Population differentiation was found between Namibia and South Africa.
• Strong gene flow occurs among the three South African stocks.
• Fisheries management should be based both on life-history and genetic data.

Silver kob (Argyrosomus inodorus) is a sciaenid fish that has been targeted for more than 150 years by commercial and recreational fisheries in the coastal waters of Namibia and South Africa, where four main stocks have been hypothesised. In the present study, recently developed molecular markers were utilized to evaluate levels of genetic diversity and population structuring among such stocks. Moderate levels of genetic diversity and signatures of bottlenecking were found in the South African stocks (South Western Cape, Southern Cape and South Eastern Cape). Significant population genetic differentiation was detected between Namibia and South Africa, but not among the three putative South African stocks, indicating that the main oceanographic barrier for silver kob populations is to be found in the cool-temperate Benguela region, corroborating recent genetic studies. The lack of genetic structuring in South African waters indicates strong gene flow among the 3 South African putative stocks, which are characterized by distinct age and growth patterns. Thus, in order to guarantee a successful recovery of silver kob stocks, genetic findings should be used in conjunction with life-history and behavioral data to tailor future management measures aimed at mitigating the effects of different fisheries throughout the species’ distribution range.