OCCURRENCE AND REDESCRIPTION OF THRYSSA SETIROSTRIS ( BROUSSONET , 1782 ) ( CLUPIFORMES , ENGRAULIDAE ) FROM IRAQI MARINE WATER

Nine fish specimens of Thryssa setirostris (Broussonet, 1782) were collected from the Arabian Gulf, during the period from July 2015 to April 2016. Because of the scarcity of this fish and overlapping and ambiguous of its taxonomic characters with other Thryssa spp., a detailed taxonomic study was conducted. The present study includes the most important meristic and morphometric characteristics. The mean of the total length of the specimens was 149.67 mm; dorsal fin consists of 12 rays, anal fin with 34-37 rays and pectoral fin with 12-13 rays; Gill rakers were 4 upper,1 medial and10 lower. The most important character that isolates T. setiristis from other close Thryssa spp. is the maxilla which is considered very long and reach beyond the tip of the pectoral fin. INTRODUCTION Clupeid fishes is a group of the most important global commercial fish, which include wellknown fishes as herrings, sardines and anchovies (Li and Orti, 2007); According to Froese and Pauly (2018) this group is divided into seven families Dentricipidae, Pristigasteridae, Engraulidae, Clupeidae, Chirocentridae, Dussumieriidae and Sundusalangidae. Engraulidae are distributed in all marine habitats, extended from 60 ° N to 50°S. They are abundant along the Indo-Pacific coasts, Atlantic and Indian oceans (Whitehead et al., 1988; Froese and Pauly, 2018). The engrulids characterized by having prominent snout (overhanging the mouth), single dorsal fin without spines, maxilla well extends behind the eye and scutes are present in most species (Young et al., 1994; Carpenter et al., 1997). This family comprises 17 valid genera, including Thryssa. This genus has 31 nominal species, mostly distributed in Indo-Pacific regions, and the Indian Ocean including Gulf of Oman; they are abundant in the Arafura Sea (Froese and Pauly, 2018). Kuronuma and Abe (1972, 1986) mentioned Thryssa mystax in both studies, while the latter mentioned T. purava, T. malabarica and T. hamiltonii in the Arabian gulf. Carpenter et al. (1997) mentioned five species vis., T. baelama, T. dussumieri, T. hamiltonii, T. vitrirostris and T. whiteheadi. Bishop (2003) mentioned six species of Engraulidae off Kuwait, including three species of Thryssa but he didn’t mention T. setirostris. Al-Faisal (2012) published a taxonomic study of three species of Thryssa including T. whiteheadi, T. mystax and T. vitrirostris. Six species of Thryssa were recorded in Iraq, including T. setirostris (Nader and Jawdat, 1977; Coad, 1991; http://dx.doi.org/10.26842/binhm.7.2018.15.2.0123


INTRODUCTION
Clupeid fishes is a group of the most important global commercial fish, which include wellknown fishes as herrings, sardines and anchovies (Li and Orti, 2007); According to Froese and Pauly (2018) this group is divided into seven families Dentricipidae, Pristigasteridae, Engraulidae, Clupeidae, Chirocentridae, Dussumieriidae and Sundusalangidae.

MATERIALS AND METHODS
Nine specimens of T. setirostris (Broussonet,1782) were collected during the period from July 2015 till April 2016 from the north western Arabian Gulf (48° 44′ to 48° 46′ N; 29° 46′ to 29° 47′ E); Fish specimens were caught by means of a trawl net, and kept in ice, then transferred to the laboratory where it was examined as soon as possible.Morphometric and meristic measurements were achieved according to Wangratana (1987).Fine characters were detected under Meiji dissecting microscope.
Total, fork and standard lengths were measured by scale measurement to the nearest 0.1 mm, lengths of different morphometric terms were measured using digital vernier; the ranges of measurements were given followed by means between parenthesis.

RESULTS AND DISCUSSION
Thirty nine parameters were detected from nine specimens of long jaw thryssa Thryssa setirostris (Pl. 1) from the Iraqi marine water.

Table (2):
The ratio of parameters of T. setirosris to standard length Total length/ Standard length 122.555%, body depth/standard length 24.322%, head length/standard length 20.266% (Tab.2).T. setirostris has very short rounded snout with its tip lay on the equator of the eye, the maxilla being very long, reaches the tip of the pectoral fin (Pl.1).
In general, fish species diversity in the Arabian Gulf is rather irregular, mainly because the deplete of water temperature in winter is also irregular, thus the diversity of individual species in the Gulf may fluctuate from year to another (Krupp and Müller, 1994).The Arabian Gulf is less biologically diverse than the adjacent Indian Ocean due to extreme environmental conditions (Al-Abdulrazzak et al., 2015); the Engraulids are small to moderate size fishes.However, some records refer to considerable fish size (Varghese et al., 2013).Fricke et al. (2018) mentioned 24 species of Thryssa, all distributed in tropical and subtropical marine environments around the world (Froese and Pauly, 2018) et al. (1997) there are five Thryssa species in the Arabian Gulf excluding T. setirostris, this species was firstly recorded in the Gulf by Nader and Jawdat (1977).
There are reports of overlapping and ambiguous taxonomic characters among the species of Engraulidae in general and especially in Thryssa, this might be resulting in misidentification of species and presentation of incorrect data (Ma et al., 2015;Gangan et al., 2016).
The identification of Thryssa species is usually based on combination of some characters such as the length of maxilla which may either being short (reach the preopercular), or medium (reach gill slits), or long (reach base of pectoral fins), or some even very long (reach pelvic fin base or beyond) (Whitehead et al., 1988).In most Thryssa species the first supramaxilla is minute or lost while the second supramaxilla is prominent (Ganga, 2015), those with or without first supramaxilla, and the level of tip of snout with a line drawn through mid-eye as in Plate 1, comprises some species including T. setirostris (Whitehead et al., 1988), T. setirostris differ from other species in this group by having very long maxilla.Randall (1995) recorded T. setirostris (Broussonet, 1782)from Gulf of Oman, he mentioned the number of rays of anal and pectoral fins which are in the same range with the specimens of the present study ; Moreover, the rays of the dorsal fin in the present study are 12 while in Randall (1995) they were 14-15 (Tab.3); from the other hand, Ma et al. (2015) mentioned that the dorsal fin of T. setirostris (Broussonet, 1782)of Taiwan has 11-12 rays.Iwatsucki (2013) stated that the meristic characters of fish may varied in different habitats,the dorsal rays of T. setirostris (Broussonet, 1782) are different in number from that of T. whiteheadi Wongranata, 1983 andT. vitirostris (Gilchrist &Thompson, 1908) (Tab. 3), but has the same range of the dorsal rays of T. hamiltonii, Gray,1835 and within the range of the number of rays of the anal fin of the same species (Tab.2).T. setirostris (Broussonet, 1782)differ from T. hamiltonii Gray,1835 by having very long maxilla (Ganga, 2015), T. dussumieri (Valenciennes, 1848) is very close in appearance to T. setirostris (Broussonet, 1782), again the latter is different by having a very long maxilla.

Table ( 3
):Comparative measurements of fin rays and gill rackers of Thryssa spp.*Species identification confirmed by Dr. Uwe Zajong, Germany.