Genetic connectivity patterns in an endangered species: the dusky grouper (Epinephelus marginatus)

Abstract

The dusky grouper Epinephelus marginatus is a popular and commercial fish and it is seen as a flag species for conservation purposes and for the establishment of coastal Marine Protected Areas in the Mediterranean region. Due to many years of over-exploitation combined with its site fidelity and sex change behaviour it has been declared endangered by the IUCN red list. Herein we analysed the genetic structure of the dusky grouper within the Mediterranean Sea and adjacent Atlantic waters using 11 highly polymorphic microsatellite markers. E. marginatus showed a weak but significant genetic population structure and was not panmictic throughout the studied range. Genetic differentiation between the central-eastern Atlantic and the Mediterranean basin was putatively based on present and historical events. Samples from Algeria were significantly differentiated from other Mediterranean localities, probably due to historical and present oceanographic processes forming a complex pattern of retention and advection on the West African Mediterranean coast. Based on these results, we propose three different management or conservation units: Senegal (central-eastern Atlantic), the West African Mediterranean coast (Algeria) and the rest of the Mediterranean locations, which are not significantly differentiated, although, clustering of locations with Atlantic water influence is observed. We suggest a Mediterranean-wide network of interconnected Marine Protected Areas, taking genetic information into account, as an essential conservation and management tool for the protection and long-term survival of the endangered dusky grouper.