NEW RECORD OF GIANT DEVIL RAY (CHONDRICHTHYES: MYLIOBATIDAE) FROM ORAN BAY (WESTERN MEDITERRANEAN SEA)

The present paper reports a new record of Giant devil ray Mobula mobular (Bonnaterre, 1788) from western Algerian waters that is encountered for the first time in that coast since its first description in 1901 and last observation in late 80’s. This elasmobranch is categorized as endangered on the IUCN Red List (Endangered A2d ver 3.1) and is likely to be the rarest of the nine species of Mobula genus. Occasionally it is captured in Mediterranean Sea by purse seines, bottom and pelagic trawls, pelagic nets, bottom longlines, drifters and harpoons. The specimen stranded in “la Madrague Beach” in Western Algerian coasts. Its disc length was measuring 108.96 cm and disc width was 226.02 cm. This Myliobatidae is rarely seen with daily landed fish at Oran fishery. Up to date no explicit reason can be given for the strand of M. mobular but ghost fishing and important maritime traffic stay the most plausible cause of this incident.


INTRODUCTION
Mobula mobular is a semi-pelagic or pelagic over the continental shelf; gregarious; met often near the surface, swimming in vertical undulations from its broad pectoral fins, occasionally jumping out of the water, but also floating motionless; can also rest on the bottom (Fischer et al.,1987). Satellite tag data for three M. mobular individuals in the Messina Strait, central Mediterranean Sea, have shown that they spent >80% of their time within the upper 50 m of the water column and dived to 700 m depth (Canese et al., 2011). Mobula mobular is aplacental viviparous (one or two embryos). Feeds on small planktonic fish and crustaceans filtered through its gill plates (Abudaya et al., 2017).
Also, this species is categorized as endangered on the IUCN Red List (Endangered A2d ver 3.1) and is likely to be the rarest of the nine species of Mobula genus (Notarbartolo di Sciara et al., 2015). Occasionally it is captured in Mediterranean Sea by purse seines, bottom and pelagic trawls, pelagic nets, bottom longlines, drifters and harpoons (FAO, 2009).
Algeria, Greece, Italy, Spain, Tunisia, Turkey and Ukraine are together responsible for slightly more than 80 % of total landings in the Mediterranean and the Black Sea. Between the year 2000 and 2013: 115 400 t were landed in Algerian fisheries occupying the third place after Italy 249 500t and Turkey 459 400 t (FAO, 2016). The ranking of capture fisheries production in 2014 and 2016 total catches continued to be dominated by Turkey: 321 800 t (26 % of total landings), followed by Italy: 185 300 t (16%), Algeria: 96 300 t (8%) and Greece: 65 700 t (5%) (FAO, 2018).
In the western Mediterranean, landings by weight are dominated by Algeria (37 %), Spain (29 %) and Italy (19 %), which account for 85 percent of all landings in the sub region, followed by Morocco (10 %) and France (5 %). approximately 30 % of total revenue in the region. Turkey, Egypt, Spain, Tunisia, Greece and Algeria, in addition to Italy, remain the countries producing the highest revenue from fisheries in the GFCM (General Fisheries Commission for the Mediterranean) area of application (FAO, 2018).
Incidental catches of vulnerable species as M. mobular taken as by-catch in many fisheries can be highly correlated to a recent report of the FAO concerning the state of Mediterranean and Black Sea Fisheries (FAO, 2016) stating that in those areas, a discard value corresponding to 20-35 % of total catch has been calculated (Sartor et al., 2003;EU, 2011;Piroddi et al., 2014in FAO, 2016. The trawling discard Ind.Fish.Res.J. Vol. 25 No. 1 June 2019: rate for the French Mediterranean was estimated between 27 and 40 % (Ifremer, 2010;Bultel et al., 2015in FAO, 2016. In Morocco, trawler fisheries (mainly catching cephalopods and/or shrimp) are associated with higher rates of discards: between 12 and 46 % (Kelleher, 2005;Belhabib et al., 2013in FAO, 2016. In Algeria, high values of discards of up to 50 %, mainly related to the shrimp fishery, have also been recorded (Bouaicha, 2011;Belhabib et al., 2013in FAO, 2016 and for pelagic trawl landing values accounted for around 20% in 2010 (MPRH, 2011). In the Turkish and Bulgaria Black Sea, discard rates for pelagic trawls are estimated to be around 5.1 % of total catch (Kelleher, 2005;Keskin et al., 2015in FAO, 2016. Despite the increasing catches worldwide, dramatic declines in mobulid catches have been documented in some areas, suggesting serial depletions through over-fishing. Mobulids are caught as by-catch in purse-seine and trawl fisheries as well as netting programs (e.g. Philippines: Alava et al., 2002in Couturier et al., 2012. As a result, harmonized methodologies for data collection on discards (FAO, 2018din FAO, 2018 and incidental catches of vulnerable species (FAO, 2018e in FAO, 2018 were produced to support the implementation of the bycatch monitoring program, which was first launched in seven countries (Algeria, Lebanon, Montenegro, Morocco, Tunisia, Turkey and Ukraine) and included training of onboard observers and, as appropriate, the development of awareness material (FAO, 2018).
Although early historical accounts painted devil and manta rays as 'diabolical creatures' and 'ferocious brutes', accusing them of stealing boats and deliberately killing divers (Gill, 1908;Saenz-Arroyo et al., 2006), it is now known that these rays are harmless to humans and feed mainly on zooplankton. Fisheries for mobulids are considered to be unsustainable because of large, directed catches coupled with the low fecundity and conservative life history of this group. Estimates of the world global catch of mobulids have increased from 900 t in 2000 to >3300 t in 2007 (FAO, 2009;Lack & Sant, 2009in Couturier et al., 2012. Although mobulids have been recorded for over 400 years, critical knowledge gaps still compromise the ability to assess the status of these species. There has been a marked increase in the number of published studies on mobulids since 1990, particularly for the genus Manta, although the genus Mobula remains poorly understood (Couturier et al., 2012). Literature reports works on this Myliobatidae in Mediterranean: Notarbartolo-di-Sciara, 1987;Bustamante et al., 2016 on systematics;Bradai & Capapé, 2001;Celona, 2004;Correia et al., 2008;Scacco et al., 2009;Bello et al., 2012;Holcer et al., 2012;Yaglioglu et al., 2013;Fortuna et al., 2014;Baºusta & Özbek, 2017;Abudaya et al., 2017 on occurrence and fisheries, Canese et al., 2011;Couturier et al., 2012;Notarbartolo di Sciara et al., 2015;Duffy & Tindale, 2018;Sakalli, 2017 on ecobiology and behaviour of M. mobular. For Algerian waters works are limited to old descriptions of Pellegrin, 1901;Dieuzeide et al., 1953also McEachran & Capape.1984Fisher et al., 1987

MATERIALS AND METHODS
On 5 th September 2017 a specimen of M. mobular (Bonnaterre, 1788) stranded at "la Madrague" beach 35º46'2.54"N, 0º48'48.96"O ( Figure. 1) in the western Algerian coast (Oran Bay). FAO identification sheet (Bauchot, 1987) was used to identify M. mobular. All measurements were made in situ to the nearest millimeter (Table 1). Unfortunately, the specimen was in advanced state of deterioration and the tail was missing, some measures were not taken as well as color of the back, so total length was measured from cephalic fins to the end of the tail spine and all measurements made on M. mobular specimen were reported as percentages of total length.

RESULT AND DISCUSSION Result
M. mobular is a mobulid rarely encountered in its natural environment (Oran Bay) as in local fisheries, it is generally taken as a bycatch in trawl fisheries and the only specimen took as object of our study is suspected to be a victim of ghost fishing, a devastating practice quite common in the area (pers.obs). Stranded M. mobular (Figure 2) was characterized by a diamond-shaped disc, nearly twice as wide as long, its anterior edges almost rectilinear, its lateral angles very acute and its posterior edges clearly concave. Head wide, its front part distinct from the disc. Tail containing a long spine with prickles. Anterior part of the pectoral fins forming two long cephalic fins. Eyes and spiracles in lateral position; mouth on the ventral side of the head, devoid of fleshy taste buds; over the entire length of the jaws (Fischer et al.,1987) (Figure 2). Measurements were made on biometric characteristics of M. mobular stranded on "la Madrague beach", and description are resumed in table 1. It appears that measurements reported as percentage of total length (TL) were as follows: Disc Length (82.56%), Disc width (171.27%), Tail spine length (136.42%), Eye diameter (4.73%), Mouth width (5.24%), Clasper (10.71%), Pre-oral length (7.56%), Pre-orbital length (19.28%), Pectoral fin (convex length) (132.14%), Pectoral fin (concave length) (78.44%), Cephalic fin length (16.51%), Cephalic fin width (5.36%), Distance between cephalic fins (16.50%), Cranial width (21.86%), Preoral length (8.42%). Ind.Fish.Res.J. Vol. 25 No.

Discussion
The length of Algerian coastline is about 1622 km (PAP RAC/PAM, 2015-Ministry of the Environment) and as stated previously, M. mobular haven't been encountered in Western Algerian coast (Oran Bay) for more than 30 years since Pellegrin, 1901;Dieuzeide et al.,1953also McEachran & Capape.1984and Fisher et al.,1987 descriptions. There were only observations and works of Hemida et al., 2002 in Central and Eastern Algerian waters but no information exists on its occurrence in the Western Algerian waters. Population trends and behavior of this mobulid are difficult to obtain given that the majority of studies available in the literature were mainly based on visual observations (Holcer et al., 2012;Fortuna et al., 2014) of population of that giant aquatic animals or limited to only 1 or two specimens as is the case of our study (table 2).

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According to UNEP/CMS, 2014, Notarbartolo di Sciara et al., 2015, Arnoud, 2018, giant devil ray (Mobula mobular) is the largest species of the genus Mobula and has a very low reproductive capacity. Its geographic range is limited to the Mediterranean Sea and possibly adjoining North Atlantic waters. This species is taken as bycatch in many different fisheries (most notably in pelagic driftnets) in several locations within its range. There are no overall regional population estimates for this species. A report of the first stranding of this mobulid species in Oran Bay can help us to trace a precise trajectory of this migratory species beginning in Alboran Sea and fill gaps concerning its population ecobiology.
Generally, it occurs in low densities (with group sizes of one to four individuals) throughout its range, although a recent episode in which these rays were mass captured off Gaza indicates that the species may occasionally occur in large aggregations. This species occurs both in neritic (Notarbartolo di Sciara & Serena 1988, Bradaï & Capapé 2001, Scacco et al., 2009, Holcer et al., 2012in Notarbartolo di Sciara et al., 2015 and offshore (Canese et al., 2011in Notarbartolo di Sciara et al., 2015 waters ranging in depth from a few tens of meters to several thousand meters. The main threat to the Mediterranean giant devil ray is fishing, although the species is rarely targeted and is usually caught accidentally. Unfortunately, this elasmobranch is sometimes targeted as was the case in Gaza strip on 26 th February 2013 where nearly 500 individuals were captured by purse seine vessels before being consumed or devoid of their precious fins (Couturier et al., 2013). In reality, according to the NGO IFAW (International Fund for Animal Welfare) (Elsayed, 2016), gills are also used in traditional Chinese medicine to treat ailments such as asthma, rashes, chicken pox or even cancer. W here approximately, a single ray can give up to 3.5 kilograms of dried gills, which can be sold up to 502 € per kilo in China. W ater pollution mainly hydrocarbons, solid wastes as plastic can contribute a lot to harm these creatures may be swallowing hundreds of plastic particles a day. Debris has been recognized as a global environmental problem including within deep habitats and recent studies showed that microplastic pollution can impact filterfeeding marine megafauna, namely mobulid rays, filter-feeding sharks, and baleen whales (Anastasopoulou et al., 2013;Germanov et al., 2018) Related to conservation strategy Lawson et al., (2017) (Davies & Laura, 2015). To our vision, it seems insufficient to protect such epipelagic marine organisms that are encountered from tens to hundreds of meters. According to local fisherman (seiner owner) witnesses, it is very rare to meet or capture M. mobular in Oran Bay, since 2015 this elasmobranch Ind.Fish.Res.J. Vol. 25 No. 1 June 2019: was met only two times in different places, 1 st at "Pointe de l'aiguille "and the 2 nd at Cape Falcon where they were swimming slowly very close to the surface confirming that the species frequents the western Algerian coasts and probably a small population exists.

CONCLUSION
Water pollution (mainly hydrocarbons, solid waste as plastic) and important maritime traffic can contribute a lot to harm these inoffensive animals that haven't been observed for more than 30 years in that part of the Mediterranean, but up to date no explicit reason can be given for the real strand of Mobula mobular in "la Madrague" beach but ghost fishing and important maritime traffic (commercial, tourism) stay the most plausible cause of this incident. Research on M. mobular is very scarce and more studies should focus on its occurrence by visual observation and/or GPS tagging, ecobiology, distribution, reproduction and nursery areas should be identified and fishing should strictly been prohibited along Algerian coasts and in the Mediterranean Sea.