First Indo-Pacific fish species from the Black Sea coast of Turkey : Shrimp scad Alepes djedaba ( Forsskål , 1775 ) ( Carangidae )

One specimen of shrimp scad Alepes djedaba (Forsskål, 1775) was caught by using fish net at a depth of 30 m on 11 October 2017 from Sinop Bay, the West Black Sea. With the present study, A. djedaba is first lessepsian fish species in the Black Sea coast of Turkey. The migration of IndoPacific species to the Black Sea indicate that climate change is getting an important issue both for marine biodiversity and fisheries in the Black Sea.


Introduction
Nowadays, many alien fish species, which entered the Mediterranean through the Suez Canal, have established dense populations in the north-eastern coastal waters of Turkey (Turan et al., 2016).
The family of Carangidae comprises of 140 species in 32 genera of worldwide (Nelson, 2006).Species of Allepes genus are characterized by following characteristics: dorsal accessory lateral line terminating in front of spinous dorsal fin, teeth in both jaws consisting of the single row of continuous, small comb like teeth.The shrimp scad, Alepes djedaba (Forsskål, 1775), is a pelagic species inhabiting inshore waters, where it forms populations near rock reefs, often in turbid waters.Alepes djedaba is in competition with some native zooplanktivorous species (Carpenter et al., 1997).A. djedaba is a species of widespread tropical marine fish of the Carangidae family.This species is widespread in tropical areas of the Indo-Pasific (Red Sea and East Africa) through the Suez Canal (Golani, 1998).A. djedaba can be misidentified with several other species of the Carangidae family.A few Caranx species and Pseudocaranx dentex have a similar ellipsoidal, compressed body shape and a line of scutes along the lateral line.However, the posterior part of their pectoral fins, when folded along the flanks, does not overlap the first scutes.A. djedaba is widely distributed in the Indo-Pacific Ocean (Otero et al., 2013).
A. djedaba was first reported from the north-eastern Mediterranean part of Turkey by Akyüz (1957), and then northward extension was reported in the the Aegean Sea coast of Turkey (Geldiay, 1969) and recently from the Sea of Marmara (Artüz and Kubanç, 2014) in Turkish marine waters.In this study, we reported the Black Sea extension of Alepes djedaba from Sinop coast as a first lessepsian fish species from the Black Sea coast of Turkey.

Material and Methods
One specimen of shrimp scad A.djedaba was caught by using fish net at a depth of 30 m on 11 October 2017 from Sinop Bay, the West Black Sea (Figure 1).The coordinates and sea surface temperature of sampling site were 42°00'10.8"N35°11'02.5"Eand 16.5 0 C, respectively.

Result
All measurements, morphological descriptions and colorations of the captured specimen were agree with previous descriptions given by Smith-Vaniz (1986) and Nelson (2006) and the diagnostic features of the captured A. djedaba specimen were compared with previously reported studies, Smith-Vaniz (1986), Gücü et al., (1994), Iwatsuki and Kimura (1996) and Artüz and Kubanç (2014) (Table 1).
The captured specimen of A. djedaba was 169 mm in total length, 126 mm in standard length and 52.75 g in total weight.Pale greenish blue color above, silvery white color below, lateral of body with yellow lane, caudal fin yellow, operculum with black spot on margin, the pectoral fin is falcate.Upper jaw anteriorly with two unsteady lines of short conical teeth posteriorly internal surface of jaw paved with blunt teeth.Gill rakers on first gill arch: 10 on upper part, 28 on lower.Meristic counts were: D1 VIII; D2 I+25; A II, I+19; C 26; P I+19; V I+6.Morphometric measurements and meristic counts of the captured specimen are given at Table 1

Discussion
The number of lessepsian fish migrants in the Mediterranean Sea has rapidly increased in recent years (Gurlek et al., 2016;Doğdu et al., 2016).Moreover, occurrence of the Atlanto-Mediterranean species in the Black Sea has also been increased (Yağlıoğlu et al., 2014 andLipej et al., 2017).In the president study, A. djedaba is reported as second Indo-Paficic species in the Black Sea since the first Indo-Pacififc species Sphyraena obtusata was given by Boltachev (2009).The increase in water temperature has been considered as a main reason for the increasing entry of Indo-Pacific species in the Mediterranean Sea (Ben Rais Lasram et al., 2010;Golani, 2010;Turan et al. 2016).Turan et al. (2016) reported that there is an increased trend of temperature for the Black Se due to global climate change.Turan et al. (2016) also indicated that the increased trend of temperature may increase the number of Mediterranean Atlantic and lessepsian fish species in the Black Sea.
While the captured one specimens of A. djedaba do not necessarily indicate existence of an established population in the Black Sea, but this species apparently migrate from the Marmara Sea via the Istanbul Strait (Bosphorus) to the Black Sea, since it was reported from the Marmara Sea by Artüz and Kubanç (2014).Therefore, the Sea of Marmara is a very important biological corridor for migratory species from both the Black Sea and the Mediterranean Sea, and the Turkish straits form an "acclimatization zone" for transiting species, allowing those from the Mediterranean to adjust to the different environmental conditions in the Black Sea.
The abundance and expansion of A. djedaba should be monitored to be able to follow its impacts on native fauna in the Black Sea.Moreover, settlement process of A. djedaba in the Black Sea will probably be accelerated or facilitated by increased trend of water temperature by global climate change as indicated in the Figure 3 and 4.

Figure 3 .
Figure 3.The sea surface temperature from İstanbul Black sea coast between 1970 and 2011 (modified from Turan et al. 2016).

Figure 4 .
Figure 4.The sea surface temperature from Samsun coast between 1970 and 2011 (modified from Turan et al. 2016).

Table 1 .
. Morphometric and meristic measurements of the captured A.djedaba, compared with the previous studies.