Introduction

The genus Photopectoralis was originally described by Sparks et al. in 2005 and contains four species, two of which are interest here: P. aureus (Abe and Haneda, 1972, Western Pacific region from Taiwan to Indonesia; Gulf of Thailand, Timor Sea and Arafura Sea (Froese and Pauly, 2016); P. bindus (Valenciennes, 1835), Indo-West Pacific region. It has been recorded from Port Sudan on the Red Sea, Arabian Gulf, and westward to Japan, and Australia (Russell and Houston, 1989). Photopectoralis hataii (Abe and Haneda, 1972), the distribution of this species is confined to waters around Indonesia, Western Central pacific region (Froese & Pauly, 2016); and P. panayensis (Kimura and Dunlap, 2003), it only found in waters around Philippines (Froese and Pauly, 2016). Photopectoralis aureus and P. bindus are marine species, but enter brackish water (Woodland et al., 2001; Riede, 2004), while P. hataii and P. panayensis are totally marine species (Froese and Pauly, 2016).

In the Arabian Gulf area, P. bindus was reported from Iraq (Hussain et al., 1988), Iran (Assadi and Dehghani, 1997), Kuwait (Bishop, 2003), Bahrain (Al-Baharna, 1986). This species was recorded from the east part of Al-Hammar Marsh, 50 Km north of Basrah City (Mohamed et al., 2014). Shatt al-Basrah Canal, which connect the greater marsh area of lower Mesopotamia to Khor al-Zubair, the marine environment of Iraq has facilitated the arrival of this species to this peculiar marsh area.

In the present study, the presence of P. bindus in the middle reaches of Shatt al-Arab River, a freshwater environment is reported. In addition, a sustainable population of this species was discovered for the first time in this area.

1 Materials and Methods

In November 2015, a population of Photopectoralis bindus was discovered in the cages designed for common carp Cyprinus carpio aquaculture with depth of not more than 2.5 m. These cages were built in an area at the middle reaches of Shatt al-Arab River at the centre of Basrah City (Figure 1).This location is 90 Km north of the total marine environment at the north-west of the Arabian Gulf. The cages at depth of 4 m from the river surface. Water salinity at the cage’s location range 2-11‰ (Figure 2).No vertical zonation with fresh water on top and brackish or marine water below was present in Shatt al-Arab Ricer as a whole or at the cage’s location. Thirty specimens were collected from the cages (Figure 3) and measured fresh to the nearest 0.1 mm and fixed in 10% formaldehyde/seawater solution for 3 weeks and transferred to 70% ethanol/distilled water solution for long-term preservation. The specimens were deposited in the fish collection of the Marine Science Centre, University of Basrah, Iraq. Body measurements were determined using dial calipers. Morphometric and meristic details were recorded following Kimura et al., 2003, 2005 and presented in Table 1. Eschmeyer (2015) and Fricke (2015) were used for the taxonomic status of the species, spelling of species name, and taxonomic reference, respectively. The length-weight relationship was presented as W = aTL^b, and transformed into its logarithmic expression: log W = log (a) + b x log (TL) to assess other potential values (Sparre et al., 1989; Froese, 2006) (Figure 4).

2 Results

Photopectoralis bindus exhibits species-specific characters: deep, oval body and strongly compressed, mainly in the lower part. Body with convex ventral profile. Abdomen before anal more strongly convex. Slightly concave occipital profile. Mouth parts after protracting slightly directed downward. Commencement of the Gape of mouth slightly above level of lower border of eye. Concave Mandible somewhat concave. Small, numerous teeth in both the jaws. Top of the head with two small spines located opposite the front border of the eye. Lower margin of pre-opercle with fine serration. Lateral line with two forms, straight and less convex near the dorsal profile and the middle of the soft dorsal, then diminished posteriorly. Short ventral fins not reaching half way to the anus with a long axillary scale. Deeply forked caudal fin with spreading lobes. Body and abdomen silvery with abdomen more silvery. Dark irregular and zigzag pattern commencing immediately behind head and reaching the end of the soft dorsal. Downward, extends to less than half height. Spines of the dorsal fin black. Membrane between the second and fifth spines with a bright orange blotch. Grey dots on tip of snout and ventral half of body. Pectoral axil dotted black. Basal part of spines of anal fin with faint yellow colour. Caudal posterior margins dusky.

3 Discussion

The range of total length of the specimens obtained in the present study for P. bindus is within the length given for this species (68-90 mm) (Table 1). The maximum length obtained for the present specimens falls just below the maximum total length given (110 mm) given for P. bindus (Randall, 1995; Froese and Pauly, 2016). The sample size in the present study is small and does not represent all length groups. Therefore, from the present dataset it is uncertain whether P. bindus exhibits allometric growth.

Hussain et al. (1988) recorded P. bindus from the marine waters of Iraq for the first time; Mohamed et al. (2014) have reported it from the Al-Hmmar marsh, now, this species is recorded from another freshwater system, Shatt al-Arab River to denote the 3^rd appearance of P. bindus in the Iraqi waters. The find of 30 P. bindus specimens in Shatt al-Arab River, Basrah, Iraq, indicates that this species was able to establish a sustainable population in totally complete environment to what it is regularly live in. The values of a and b obtained from LWR are less and higher respectively than those obtained western region of Indonesia, Strait of Hormuz, Arabian Gulf and Kakinada, India (Froese and Pauly, 2016).

Unlike the estuarine mixing of the River Elbe, Germany is about 50 Km downstream of Hamburg with marine water currents running in the lower layers of the river (Hofmann et al., 2005). Shatt al-Arab River has such under water currents to about 75 KM south of the cage’s location (Al-Badran and Mahmood, 2006; Al-Mayahi, 2011). This mean that individuals of P. bindus can stands the low salinity of Shatt al-Arab River, manage to reach the middle reaches of this river, and succeeded to form a population in the cages. This situation is different from that present in the Al-Hammar marsh, where Shatt al-Basrah canal, a marine water environment is directly connected to the marsh area. In such circumstances, individuals of P. bindus have no difficulty reaching the freshwater area of the marsh.

The previous and the recent ichthyologic surveys that performed in Shatt al-Arab River for the last two years did not show the presence of the population of P. bindus. Therefore, the establishment of this population has happened fairy soon and could be early in year 2015. Some variation in the abundance of both phyto and zooplanktons were noticed in Shatt al-Arab River in late 2014 and early 2015 (Abbas et al., 2015; Fawzi and Mahdi, 2014) and such changes could trigger the movement of the individuals of P. bindus up Shatt al-Arab River. More investigations are needed in this aspect and also to study the biology of this newly established population.