Critically endangered fish species of Turkish Seas ( Mediterranean and Aegean ) : Longfin gurnard , Chelidonichthys obscurus ( Walbaum , 1792 )

Longfin gurnard Chelidonichthys obscurus (Walbaum, 1792) is reported several times from various researchers in the checklist of Turkish marine fishes. However, last three decades, the species is not occurred in the distributional range, comprising the northeastern Mediterranean Sea and Aegean Sea coast of Turkey. It is possibly critically endangered or absent in the Turkish Seas. Moreover, there has no any biological study been carried out on C. obscurus in Turkey. C. obscurus is considered to be critically endangered or regionally extinct in the eastern Mediterranean Sea and Aegean Sea coast of Turkey. This species might be recorded as “Critically Endangered” in the Mediterranean and Aegean Sea coast of Turkey in the IUCN Red List of Threatened Species.


Introduction
In some cases, several fish species have previously been reported from Turkish Seas where essential information is not available to support their occurrence.If no specimen of a species has yet been collected from a region, they should not be accepted as a part of the local ichthyofauna until a relevant individual specimen has been provided.
The family Triglidae is represented by four genus (Chelidonichthys, Trigla, Eutrigla, and Lepidotrigla) with 8 valid species, distributed along the Turkish Seas (Golani et al., 2006, Turan, 2007;Froese and Pauly, 2015).C. obscurus was previously considered as a synonym of Trigla obscura Bloch & Schneider, 1801.However, the status of both genus still remains doubtful and needs further investigations.C. obscurus is commonly found Eastern Atlantic: southern coasts of the British Isles to Mauritania, the Azores and Madeira; Mediterranean, but absent in northern Aegean Sea and Black Sea (Golani et al., 2006;Froese and Pauly, 2015).
C. obscurus is first reported from Turkish Seas by Akşıray (1954Akşıray ( , 1987) ) with a key to identification of the species, and then it has been added in the Checklist of the marine fishes of Turkey (Geldiay, 1969;Fischer et al., 1987;Mater and Meriç, 1996;Mater and Bilecenoglu, 1999;Bilecenoglu et 2002;Fricke et al., 2007) with a distribution in the Mediterranean and Aegean Sea coast of Turkey.However, there has been no any study or capture record on the occurrence of C. obscurus in Turkish marine waters.Therefore, in the present study, we discuss occurrence and conservation status of C. obscurus in the Turkish Seas.

Identification
Gurnard species can easily be distinguished by morphological characters.C. obscurus (Figure 1) differ from all other known Trigla species in large head armored with bony plates with many ridges and spines, but marked occipital sulcus; rostrum slightly indented; cleithrale spine (above pectoral) short.Moreover, three lower most pectoral rays free; the first spine in first fin elongated; lateral line scales plate-like without vertical expansions.Total gill rakers on the first branchial arch are between 7 to 11. Fin rays: D1 X-XI, D2 17-19, A 17-18, V I + 5, P 10+3; lateral line scales: 68-70; Vertebra: 36-37; maximum length of about 40 cm; and usually 10 to 20 cm length (Mediterranean) (Golani et al., 2006).Colour: Body red pink iridescent flanks, belly pale, pectoral fins dark blue, other fins rose.

Threats
Over-fishing pressure, habitat degradation and pollution are the main threat of declines of gurnard species.Especially, the climate change and lessepsian migration from Indo-Pacific have resulted to environmental changes in the Mediterranean, and thus serious shifts have occurred in the Mediterranean and Aegean ecosystem in the last 20 years (Turan, 2010;Ozturk and Turan, 2012).The ecosystem has also been affected by bottom trawling, which destroys the seabed communities and affects the links between the benthic and pelagic components of the system.

Conservation action
No current conservation action has been implemented.C. obscurus is probably endangered or extinct from the Turkish coasts comprising the Mediterranean and Aegean Sea.

Conservation recommendations
Up to date, last three decades, C. obscurus is not occurred in the Turkish Seas.Also, there has been no any biological study and fishery data (trawl, purse seiner, nets, and ext.) given in Turkish coasts.Moreover, we had personal communication with scientists who are well experienced at fishery in the Aegean and Mediterranean Sea that they have never seen C. obscurus in their field work.Furthermore, we have had tens of field works in the Mediterranean and Aegean Sea Coasts of Turkey for sampling gurnards and asked all fishermen for this species for two years, but we could not observe this species.Therefore, the species is critically endangered or regionally extinct in the Aegean Seas and northeastern Mediterranean coast of Turkey.
Although, C. obscurus relatively common in some parts of the Mediterranean Sea to the Atlantic coasts of northern Spain and south-west France (Quero et al., 1989;Sanches et al., 2002), and it is recorded rarely in British waters.It was reported from the western English Channel in the 19th Century (Yarrell, 1841;Couch, 1877;Day, 1880Day, -1884;;Holt et al., 1898), but was absent from lists of the regional ichthyofauna compiled during the 20 th Century (Le Danois, 1913;Le Mao, 2009).Gary and Ellis (2014) obtained a total of 82 specimens of C. obscurus that were caught in the English Channel, all from 2004 to 2013.To date, little is known about the biology of C. obscurus, and most published data are from the western Mediterranean Sea, where there have been studies of their reproductive biology (Munoz et al., 2003, as Aspitrigla obscura) and feeding habits (Moreno-Amich 1996;Morte et al., 1997;Boudaya et al., 2007) and parasites (Serecca et al., 2013).Genetic analysis should also be conducted on these existent populations to determine their genetic structure as defined for other marine species (Turan, 2006;Turan, 2008).This species should be recorded in the IUCN Red List of Threatened Species as Endangered (EN) for Mediterranean and as Critically Endangered (CR) for Turkish Mediterranean coast.

Remarks
Fishing pressures, pollution, lessepsian invasion and climate change effects may be reasons for this extinction.C. obscurus may be very fragile species against these anthropogenic effects and lost in the nature.
These anthropogenic effects and excessive harvesting of commercial fish populations in the Mediterranean region will most probably result in further declines in the occurrence and species diversity in the Turkish marine waters.