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

Abstract

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