FIRST RECORD OF THE DOUBLEBAR SEABREAM, ACANTHOPAGRUS BIFASCIATUS (ACTINOPTERYGII: PERCIFORMES: SPARIDAE), IN THE AEGEAN SEA

The present paper reports the second record of a Lessepsian migrant, Acanthopagrus bifasciatus (Forsskål, 1775), in the Mediterranean Sea and first record from the Aegean Sea. The species is distinguished by the counts of 51⁄2 scale rows between the fifth dorsal-fin spine and lateral line, dorsal and caudal fins yellow, without a dense black margin of dorsal-fin or narrow black edge along rear margin of caudal fin which is being diagnostic characters of this species.


INTRODUCTION
The seabreams are one of the most common fish species that inhabit both tropical and temperate coastal waters throughout the world. Seabreams have importance to both commercial and recreational fisheries and are favoured food fish throughout their distribution range (Smale andBuxton 1985, Sommer et al. 1996).
The double bar seabream, Acanthopagrus bifasciatus (Forsskål, 1775), was described originally from the Red Sea. It is known in shallow coastal waters (2-20 m depth) associated with reefs in the Persian Gulf (Grandcourt et al. 2004) and the western Indian Ocean (Khalaf and Disi 1997). Apart from its natural distribution area, A. bifasciatus has also been reported from the Mediterranean Sea (Ben-Souissi et al. 2014).
The present paper reports a case of an ongoing alien introduction for the Mediterranean Sea and also the first alien sparid fish in the Aegean Sea.
The fish was captured by a local fishing boat, with a trammel net at 3 m depth on a sandy/seagrass (Posidonia oceanica) bottom near a breakwater.
Morphological methods followed Iwatsuki and Heemstra (2011). The collected specimen was preserved in 4% formalin and deposited in the Fish Collection Centre of the İzmir Katip Çelebi University (IKC.PIS.1240).

RESULTS
The measurements in absolute and relative values (% of standard length, SL) are given in Table 1. Description. Body deep and compressed, lips thick, maxilla almost reaching to vertical at rear edge of pupil. Scale rows between fifth dorsal-fin spine and lateral line 5½; upper and lower jaw with 4 canine teeth. Upper jaw with 4 and lower jaw with 3 molar tooth rows. Head and body silvery; head with two vertical black bars across head and parallel to each other, first extending below angle of jaw, second wider, extending to lower edge of opercle. Silvery pigmentation between these two black bars. Infraorbital area orange and this pigmentation merging with superior part of snout. Dorsal, caudal, and pectoral fins vivid orange but hind margin of caudal fin with narrow black margin and spines of dorsal fin with tentative black pigmentation (Figs. 2A, 2B). Anal and pelvic fins blackish.

DISCUSSION
Acanthopagrus bifasciatus and its closely related species Acanthopagrus catenula (Lacepède, 1801) originating from the Red Sea and the western Indian Ocean have been recognized as attractive species also because of their intensive coloration. The morphological similarities of these two species lead to the recognition of a single species (A. bifasciatus) with two different populations of until Iwatsuki and Heemstra (2011) assigned these populations to different valid species (A. bifasciatus and A. catenula). Although morphometric and meristic characters of these two species seem to overlap, A. bifasciatus can be distinguished from A. catenula with the counts of scale rows between the fifth dorsalfin spine and lateral line (Iwatsuki and Heemstra 2011). Also, the dorsal fin of A. bifasciatus lacks a wide black margin and the caudal fin rear margin has a narrow black edge (Iwatsuki and Heemstra 2011). The measurements in absolute and relative values are in concordance with Iwatsuki and Heemstra (2011).
The number and arrangement of molariform teeth both on the upper and lower jaw are similar in descriptions of these two species but, smaller incisor teeth at the front of the upper jaw is another diagnostic character of A. bifasciatus (see Iwatsuki and Heemstra 2011). In addition, Iwatsuki and Heemstra (2011) remarked that the outer molar teeth rows of both jaws extend to the rear end of the jaws in A. bifasciatus. In our specimen, the incisor teeth at the front of the upper jaw are very conspicuous which is consistent with the observation of Iwatsuki and Heemstra (2011) and middle rows of the molar teeth of both jaws extend to the rear end of the jaws (Figs. 3A, 3B).
Marine species could be introduced in several ways such as movements through corridors, transfer on drifting logs, and by anthropogenic means such as the introduction of species by ballast water or release of aquarium specimens (Spanier and Galil 1991). Furthermore, some benthic and small size fishes could migrate from the Red Sea and could be overlooked due to their small size and morphological similarities with the native species (Engin et al. 2017, Seyhan et al. 2017. Some authors emphasize that although ballast water could be an important cause of transferring small-size invertebrates, plankton or algae, it is not suitable for adult fishes (Lockett andGomon 2001, Molnar et al. 2008). On the contrary, shipping activities, oil platforms, or similar structures, could act as artificial habitats and serve as shelter and even spawning substrate that moving slowly through the ocean especially for reef-associated fishes (Jørgensen et al. 2002, Galil 2006, Atchison et al. 2008, Yeo et al. 2010, Macreadie et al. 2011, Friedlander et al. 2014. Similarly, the species A. bifasciatus, was recorded from Tunisia eleven years ago as a result of shipping activities or marine traffic (Ben-Souissi et al. 2014) and up to date, no further record has been made which could be another indication of unintentional human activities.