The meagre Argyrosomus regius is a large Sciaenid fish known toreproduce in the eastern Atlantic and Mediterranean Sea in just five distinct andrestricted geographic areas: along the Mauritanian coast and at estuary openings (Gironde,Tagus, Guadalquivir and Nile). The biological traits of A. regius (highdispersal capabilities, high fecundity, long larval phase, overlapping generations,reproduction until 40 years of age) are, in principle, favourable to high gene flow, whichshould lead to genetic homogeneity over large geographic scales. Nevertheless, the highgeographic distances between the few reproductive areas leads one ask whether there isgenetic differentiation in this species. In the present study, the genetic differentiationof the wild A. regius was investigated across most of its natural rangefrom the Atlantic Ocean (France, Portugal, Spain, Mauritania) to the Mediterranean Sea(Egypt, Turkey), using 11 microsatellite markers previously identified in anotherSciaenid, the red drum Sciaenops ocellatus. At least two very distinctgroups could be identified, separated by the Gibraltar Strait. Genetic divergences(FST 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) andextremely high between the Aegean Sea and the Atlantic (0.098–0.168). A. regiusexhibited a very high level of genetic differentiation rarely reported in marinefishes. These results also demonstrate the existence of a sixth independent spawning areain the Menderes delta (Turkey). Factors potentially involved in this very high geneticfragmentation are discussed, including physical barriers, glaciation pulses and biologicaltraits.

Age and growth of adult gilthead seabream, Sparus aurata were determined from 332 specimens (total N = 476), collected from purse-seiners, in the south-eastern Aegean Sea from November 2006 to January 2007. The fork length and body wet weight ranged from 26.5 to 51.5 cm (mean: 36.6 ± 0.18) and from 375 to 2600 g (mean: 1009.2 ± 14.16), respectively. Age groups were varied between 2 and 7. Growth parameters were estimated as L∞ = 64.97 ± 12.93 cm, K = 0.14 ± 0.07 year−1, t0 = −2.47 ± 1.09 year−1, and index of phi-prime was Φ′ = 2.772 ± 0.51. The length–weight relationship equation of all fish was calculated as W = 0.0515 × L2.737 (r2 = 0.95). The mean condition factor was estimated as 2.058. Mortalities (M, F and Z) and exploitation rate (E) of gilthead seabream from the Aegean Sea were 0.34 year−1, 0.77 year−1, 1.11 year−1and 0.69 year−1, respectively. The result of E indicated that the population was overexploited.