First record of Atractoscion aequiden ( Sciaenidae ) from the Arabian Sea Coasts of Oman and Acanthopagrus catenula ( Sparidae ) from the Oman Sea ( Gulf of Oman ) , northwestern Indian Ocean ( Teleostei , Sciaenidae , Sparidae )

First record of Atractoscion aequidens (Sciaenidae) from the Arabian Sea Coasts of Oman and Acanthopagrus catenula (Sparidae) from the Oman Sea (Gulf of Oman), northwestern Indian Ocean (Teleostei, Sciaenidae, Sparidae).— The first record of Atractoscion aequidens from the Arabian Sea coasts of Oman and Acanthopagrus catenula from waters around City of Muscat on the Sea of Oman is reported based on one (671 mm in SL) and ten specimens (111–257 mm SL), respectively. This account represents the second record of A. aequidens in the northern Indian Ocean and the northernmost record of A. catenula in the same ocean. Morphometric and meristic data are provided for the two species and compared with those from specimens collected from other parts of the world. The southern distribution of A. catenula is corrected in this report.


Introduction
The Sciaenidae (Perciformes) comprises 291 species belonging to 66 genera and is the most morphologically diverse group in the perciform families (Eschmeyer & Fong, 2012;Eschmeyer, 2012).Trewavas (1977) recognized 27 genera and 77 species in the Indo-West Pacific, including 19 genera and 37 species in the Indian Ocean.Sasaki (1996) reviewed sciaenid fishes of the Indian Ocean and reported a total of 47 species assigned to 19 genera.The Sparidae (Perciformes) consists of approximately 134 species belonging to 35 genera and is the largest group in the sparoid families (Eschmeyer & Fong, 2012;Eschmeyer, 2012).In Omani waters in general, the Sciaenidae consist of 11 species belonging to 6 genera and the Sparidae consist of 15 species belonging to 10 genera (Randall, 1995).In the Arabian Sea coasts of Oman alone, the Sciaenidae comprise 12 species belonging to 7 genera while the Sparidae consist of 16 species belonging to 10 genera (Laith Jawad, unpub. data).
Atractoscion aequidens has a current distribution from Angola to South Africa (Chao & Trewavas, 1990).This species also occurs along eastern coasts of Australia.In the Western Indian Ocean it has been reported from off Mozambique and South Africa (Froese & Pauly, 2010).Sasaki (1996) recorded this species from the Gulf of Aden.On the other hand, Acanthopagrus catenula has a current distribution from off the Horn of Africa to off Socotra Island of Somalia, including Kenya, Mozambique, South Africa, Madagascar, Mauritius, Rodriguez and Madrakah, southern Oman (Iwatsuki & Heemstra, 2011).
In the present study the two species are recorded from the waters of Oman for the first time.The paper also includes the northernmost record of A. catenula in the Indian Ocean.

Studied material
Atractoscion aequidens (fig. 1) was captured on 7 VI 2011 and Acanthopagrus catenula (fig.2) on 15 VII 2011.A deep gill net used by local fisherman caught one specimen of the former and 10 specimens of the latter from the coasts of the city of Salalah on the Arabian Sea coasts of Oman and the coasts of the city of Muscat on the Sea of Oman, respectively.
The specimens were deposited in the fish collection of the Marine Science and Fisheries Centre, Ministry of Fisheries Wealth, Muscat, Sultanate of Oman; catalogue numbers OMMSTC 1087 and 1092 for A. aequidens and A. catenula, respectively.

Results
Morphometric and meristic details were recorded following Fischer & Bianchi (1984) for A. aequidens and Carpenter (2001) for A. catenula; the data are presented in tables 1 and 2.

Discussion
Few specimens of A. aequidens have been described from around the world and only standard length is provided.Our specimen (671 mm) is larger than most of the previously described samples but smaller than that from Natal (1,381 mm, Natal; 638 mm, Sydney, Australia; 316.6 mm and 428.6 mm, Gulf of Aden (Trewavas, 1977;Sasaki, 1996).
With only one large-sized specimen of A. aequidens, it is premature to consider that this species has established a sustainable population around its new locality.Thus, further studies are needed to assess the frequency of occurrence and to study the biological cha-  racteristics of this species so as to determine whether it has become established.However, the new record of this species may be explained by insufficient ichthyological expeditions conducted to date.
As Acanthopagrus catenula was only recently resurrected, there are no records available from the other parts of the world because it is considered as endemic to the Western Indian Ocean.Measurements or meristic data available for comparisons are hence restricted to those given by Iwatsuki & Heemstra (2011) when they redescribed the species for the first time (see table 1).The size of our specimens falls near the maximum size given by Iwatsuki & Heemstra (2011) and body proportions agree with those given by those authors (table 1).
There are several factors to explain why A. catenula has not been reported from the Sea of Oman previously.Among these we emphasize two possibilities: (i) the lack of sampling in the area prevents the detection of this species in the Sea of Oman although it has been present; (ii) due to global change such as sea water temperature, a recent natural colonisation along the northern coast of the Indian Ocean may have taken place.The capture during this study should not be regarded as accidental as 10 individuals were collected, indicating the presence of a self-sustaining population of this species in the Sea of Oman.

Table 2 .
Morphometric and meristic characteristics of Acanthopagrus catenula in the Sea of Oman compared with specimens from the literature: TL.Total length; HL.Head length; SL.Standard length; Na.Not available.Tabla 2. Características morfométricas y merísticas de Acanthopagrus catenula del mar de Omán comparadas con las de las especies registradas en la literatura.TL.Longitud total; HL.Longitud de la cabeza; SL.Longitud estándar; Na.No disponible.