Very high genetic fragmentation in a large marine fish, the meagre Argyrosomus regius (Sciaenidae, Perciformes) : impact of reproductive migration, oceanographic barriers and ecological factors

¹ SYSAAF, Station SCRIBE/INRA, Campus de Beaulieu, 35042 Rennes, France
² LABOGENA, INRA, Domaine de Vilvert, 78350 Jouy-en-Josas, France
³ IMROP, BP 22, Nouadhibou, Mauritania
⁴ Centro de Oceanografia, Faculdade de Ciências da Universidade de Lisboa, Campo Grande, 1749-016 Lisboa, Portugal
⁵ Reef Check, Wachmannstr. 25, 28209 Bremen, Germany
⁶ IRSTEA (ex-CEMAGREF), 50 av. de Verdun, 33612 Cestas, France
⁷ Ege University, Fisheries Faculty, Aquaculture Dep., 35100 Izmir, Turkey
⁸ FMD, BP 4, 17840 La Brée les Bains, France
⁹ Les Poissons du Soleil, BP 10, 34540 Balaruc-les-Bains, France
¹⁰ CNRS UMR 5554, Institut des Sciences de l’Evolution, Université de Montpellier II, 2 rue des Chantiers, 34200 Sète, France

^a Corresponding author : haffray@rennes.inra.fr

Received: 5 April 2011
Accepted: 8 June 2012

Abstract

The meagre Argyrosomus regius is a large Sciaenid fish known to reproduce in the eastern Atlantic and Mediterranean Sea in just five distinct and restricted geographic areas: along the Mauritanian coast and at estuary openings (Gironde, Tagus, Guadalquivir and Nile). The biological traits of A. regius (high dispersal capabilities, high fecundity, long larval phase, overlapping generations, reproduction until 40 years of age) are, in principle, favourable to high gene flow, which should lead to genetic homogeneity over large geographic scales. Nevertheless, the high geographic distances between the few reproductive areas leads one ask whether there is genetic differentiation in this species. In the present study, the genetic differentiation of the wild A. regius was investigated across most of its natural range from the Atlantic Ocean (France, Portugal, Spain, Mauritania) to the Mediterranean Sea (Egypt, Turkey), using 11 microsatellite markers previously identified in another Sciaenid, the red drum Sciaenops ocellatus. At least two very distinct groups could be identified, separated by the Gibraltar Strait. Genetic divergences (F_ST values) were intermediate between the Atlantic samples (0.012–0.041), high between Egypt and the Atlantic (0.06–0.107) or Aegean Sea (0.081) and extremely high between the Aegean Sea and the Atlantic (0.098–0.168). A. regius exhibited a very high level of genetic differentiation rarely reported in marine fishes. These results also demonstrate the existence of a sixth independent spawning area in the Menderes delta (Turkey). Factors potentially involved in this very high genetic fragmentation are discussed, including physical barriers, glaciation pulses and biological traits.