First records of seven marine organisms of different origins from Libya ( Mediterranean Sea )

Seven first records of species of various origins are reported from the Libyan marine environment. These are the Longfin yellowtail Seriola rivoliana, Lesser amberjack Seriola fasciata, Blunthead puffer Sphoeroides pachygaster, Golani round herring Etrumeus golanii, Blue swimmer crab Portunus segnis, Bigfin reef squid Sepioteuthis lessoniana, and the green alga Caulerpa taxifolia. The first three species are widely distributed fish seemingly expanding their range in the Mediterranean Sea, while the others are alien species, introduced in the Mediterranean through various pathways. While some were recently captured, others were identified from old collections, with dates of capture ranging between 1993 and 2017. In addition to updating the list of marine fauna and flora from Libya, the respective dates of these records represent vital information for future studies aiming at reconstructing range expansion histories and assessing spread rates in the Mediterranean Sea.


Introduction
The presence of non-indigenous species (NIS) in the Mediterranean Sea is nowadays gaining a lot of scientific attention (e.g.Katsanevakis et al. 2016;Galil et al. 2017;Zenetos et al. 2017).In fact, the Mediterranean is highly impacted by marine bioinvasions, and introduction rates seem to have increased at an alarming rate (Golani 2010;Edelist et al. 2013;Samaha et al. 2016).A relatively large number of marine species of various origins have been reported in the last few decades.NIS have entered the Mediterranean following the opening of the Suez Canal or have arrived from more distant locations, through other modes of introductions (Galil 2016;Zenetos et al. 2017).Other species, previously recorded in the tropical Atlantic but not in the Mediterranean, seem to have expanded their biogeographical ranges over the years (range-expanding species).However, for many of them direct evidence of their native or alien status in the Mediterranean is lacking, and they have been labelled as "cryptogenic" (Carlton 1996).
The seashore of Libya represents 2000 km of coastline and is characterized by a wide continental shelf that encompasses various habitats and topography (Shakman 2008;Shakman and Kinzelbach 2007a).The geographic location of Libya, in the central and "warm" part of the Mediterranean Sea is interesting, as it can host thermophilic organisms arriving from the east (Indo-Pacific origin) or expanding from the west (Tropical Atlantic origin).Scientific investigations on the Libyan marine fauna and flora started in the 1880s (reviewed in Al-Hassan and El-Silini 1999; Shakman and Kinzelbach 2007b) but information available on these species remains rare, incomplete, and fragmented (e.g.Stirn 1970;Al-Hassan and Silini 1999;Shakman and Kinzelbach 2007a;Bazairi et al. 2013).There is a serious lack of comprehensive studies on marine organisms occurring in the area and this part of the Mediterranean remains among the least known to scientists (Shakman 2008).
In the present paper, we report seven first records of marine organisms, some of which are invasive, from the coastal zone of Libya.These include four fish species, a decapod, a cephalopod, and a seaweed.All seven organisms represent first records for Libyan waters and some are among the first individuals to be recorded in the Mediterranean Sea.They are all catalogued and deposited in the collections of the Tripoli University (ZMT: Zoological Museum of Tripoli; HPTA: Herbarium Plant department of Tripoli, Algae).

CARANGIDAE Rafinesque, 1815
Seriola rivoliana Valenciennes, 1833 The Longfin yellowtail Seriola rivoliana, also known as Almaco Jack, is a circumglobal marine fish living in tropical and temperate regions, but with an unclear distribution in the eastern Atlantic (Froese and Pauly 2017).The first individual was reported from the Mediterranean Sea in year 2000 and several additional records have later been published from other locations (e.g.Castriota et al. 2002;Castriota et al. 2004;Mansour et al. 2011;Valls et al. 2011).
On 12 th February 2004, a single individual of Seriola rivoliana (Figure 1) of 221 mm SL was captured off the coast of Tripoli along the Libyan shore (32º54′51.39″N;13º14′18.76″E).The fish was caught in a trammel net at a depth of about 40-50 m over a rocky bottom covered by seaweeds.All descriptive characters, measurements and counts followed those given for S. rivoliana (Castriota et al. 2002(Castriota et al. , 2004)).The specimen is fixed in formalin and catalogued (ZMT, FISH0126).

CARANGIDAE Rafinesque, 1815
Seriola fasciata (Bloch, 1793) The Lesser amberjack Seriola fasciata is a carangid living on both sides of the Atlantic Ocean (Eschmeyer et al. 2017).It was first recorded in 1989 and quickly reported in large numbers in the central Mediterranean (Massutí and Stefanescu 1993;Andaloro and Potoschi 1997;Andaloro et al. 2005).It has also been found in several parts of the Mediterranean Sea, and has reached the easternmost coasts (e.g.Sonin et al. 2009;Crocetta et al. 2015;Jawad et al. 2015).
On 18 th July 2003, a single individual of Seriola fasciata (Figure 2) of 128 mm SL was captured off the  coast of Tripoli along the Libyan shore (32º54′51.39″N;13º14′18.76″E).The fish was caught in a trammel net at a depth of about 30-40 m over a rocky bottom covered by seaweeds.All descriptive characters, measurements and counts followed those given for S. fasciata in Fischer et al. (1981).The specimen is fixed in formalin and catalogued (ZMT, FISH0127).
On 13 th June 1993, a single individual of Sphoeroides pachygaster (Figure 3) of 325 mm SL was captured west of the city of Misrata, along the Libyan shore (32º26′29.85″N14º54′26.35″E).The fish was caught with a commercial trawler operating over a muddy bottom at a depth ranging between 60 and 80 m.The identification has been made following Tortonese (1986).The specimen is fixed in formalin and catalogued (ZST, FISH0128).

CLUPEIDAE Cuvier, 1816
Etrumeus golanii DiBattista, Randall and Bowen, 2012 The Golani round herring Etrumeus golanii is an Indo-Pacific marine fish native to the northern Red Sea (DiBattista et al. 2012).The species also occurs in the Mediterranean as a NIS since 1961 (Whitehead 1963) with an important population established in the eastern Mediterranean (El-Sayed 1994;Golani 2000;Corsini et al. 2005).It recently spread to the central Mediterranean and has quickly appeared in large quantities in Tunisia (Falautano et al. 2006;Boussellaa et al. 2016;Rafrafi-Nouira et al. 2017).
On 22 th April 2017, a school of Etrumeus golanii was captured west of the city of Misrata, along the Libyan shore (32º54′51.39″N;13º14′18.76″E).The school was landed by a purse seine operating at around 30 m, over a soft bottom.A single individual (156 mm SL, Figure 4) was collected and preserved.All descriptive characters, measurements and counts followed those given for E. golanii by DiBattista et al. ( 2012).The specimen is fixed in formalin and catalogued (ZMT, FISH0129).

PORTUNIDAE Rafinesque, 1815
Portunus segnis (Forskål, 1775) The Blue swimmer crab Portunus segnis, previously recorded in the Mediterranean Sea as P. pelagicus (Linnaeus, 1758), is a decapod native to the western Indian Ocean (Lai et al. 2010).It is among the very first species to be reported from the Mediterranean Sea following the opening of the Suez Canal and had already a large population established in the Levant in the 1920s (Galil 2011).It started to spread recently and has been recorded in various areas in the Mediterranean, including Italian and Tunisian waters (Crocetta 2006;Rabaoui et al. 2015).
On 25 th April 2017, a female specimen of Portunus segnis of 68 mm (Figure 5) carapace length (CL) was captured west of the city of Tubruk, along the Libyan shore (32º4′36.70″N;24º0′21.51″E).It was accidentally captured by a trammel net set at 30 m depth over a seagrass meadow.The specimen is fixed in formalin and catalogued (ZMT, CRS0032).
On 3 rd December 2015, one individual of Sepioteuthis lessoniana (Figure 6) of 170 mm mantle length (ML) was captured off the coast of Tripoli, along the Libyan shore (32º54′43.51″N;13º14′12.29″E).It was accidentally captured by an angler who was jigging for squids and octopus at about 10 m depth over a gravel bottom, with boulders and seaweeds.The specimen is fixed in formalin and catalogued (ZST, CEPH08).

CAULERPACEAE Kützing, 1843
Caulerpa taxifolia var.distichophylla (Sonder) Verlaque, Huisman and Procaccini Caulerpa taxifolia (M.Vahl) C. Agardh, 1817, is a well-known macrophyte (Chlorophyta: Caulerpaceae) aquarium strain that has been introduced to the Mediterranean in the 1980s, rapidly spread and generated a lot of public interest in the northwestern and central Mediterranean (Meinesz and Hesse 1991;Jousson et al. 1998;Meinesz et al. 2001).A different strain, Caulerpa taxifolia var.distichophylla, was recorded from Syria in 2003 and from various places of the eastern and central Mediterranean afterwards, including Sicily and Malta (reviewed in Bitar et al. 2017).
On 10 th March 2017, a specimen of Caulerpa taxifolia var.distichophylla (Figure 7) was captured off the coast of Tripoli, along the Libyan shore (32º54′37.77″N;13º14′35.11″E).It was collected over a sandy bottom with a seagrass meadow, probably growing on some hard structure.The specimen is fixed in formalin and catalogued (HPTA279).

Discussion
The three fish species, Seriola rivoliana, Seriola fasciata, and Sphoeroides pachygaster are all widely distributed fishes and are mostly considered as naturally expanding their distributional range in the Mediterranean Sea (Zenetos et al. 2012).Besides the first records for the coast of Libya, the individual of S. rivoliana, which was collected as early as 2004, constitutes the third (out of six records) in the Mediterranean Sea.Similarly, the importance of the records of both S. fasciata and S. pachygaster lies in the fact that they were also among the early individuals that have ever been reported from the Mediterranean Sea.Both species are nowadays present in various parts of the Mediterranean Sea (Lipej et al. 2013;Crocetta et al. 2015).The record of the Indo-Pacific fish Etrumeus golanii and the decapod Portunus segnis are also interesting because they have recently reached the central Mediterranean region and their populations are currently blooming in nearby Tunisian waters and also gaining commercial importance (Crocetta et al. 2015;Ben Souissi, pers. comm.).The Indo-Pacific squid Sepioteuthis lessoniana has already been reported from several locations in the eastern Mediterranean, but the current record constitutes the second for the central Mediterranean Sea (Crocetta et al. 2014).Finally, we hereby report the presence of Caulerpa taxifolia in Libyan waters, identified as Caulerpa taxifolia var.distichophylla.This record is the seventh record of this variety from  the Mediterranean Sea.However, we are highly cautious on the proper identification of this particular species since the two strains, both occur in the central Mediterranean (Jongma et al. 2013;Schembri et al. 2015;Mannino et al. 2017).The taxonomy of Caulerpaceae being relatively complex with variable morphologies is determined by environmental conditions.It is imperative that further samples are collected and carefully examined using genetics.
There is often a detection lag between the real arrival time and the first published record of a new species (Costello and Solow 2003).Despite that lag, documenting the arrival to a new region is crucial since it is the only measure in time and space available to scientists.Libya is among those Mediterranean countries that generally lack updated faunal and floral studies (Shakman 2008).The recorded species update the checklist of species from this country, but the respective dates of records for these species also show that an "exotic" species is often recognised but not always reported to the scientific community.This is particularly the case for the three cryptogenic fishes, which were simply kept in collection (since 1993 for S. pachygaster, 2003 for S. fasciata, and 2004 for S. rivoliana).These records remain of key importance for studying the early stages of presence of such organisms as well as their spread in the Mediterranean Sea.