Blackchin guitarfish

Blackchin guitarfish
Conservation status
	; Critically Endangered (IUCN 3.1)
	CITES Appendix II (CITES)
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Chondrichthyes
Subclass:	Elasmobranchii
Superorder:	Batoidea
Order:	Rhinopristiformes
Family:	Glaucostegidae
Genus:	Glaucostegus
Species:	G. cemiculus
Binomial name
	Glaucostegus cemiculus; Geoffroy Saint-Hilaire, 1817
Synonyms
	Glaucostegus petiti (Chabanaud, 1929); Rhinobatos cemiculus rasus Garman, 1908; Rhinobatos congolensis Giltay, 1928; Rhinobatos rasus Garman, 1908; Rhinobatus cemiculus Geoffroy Saint-Hilaire, 1817; Rhinobatus congolensis Giltay, 1928; Rhinobatus rasus Garman, 1908;

The blackchin guitarfish (Glaucostegus cemiculus, formerly Rhinobatos cemiculus)^[1] is a species of cartilaginous fish in the family Rhinobatidae. It is native to the eastern Atlantic Ocean and the Mediterranean Sea. It is a bottom-dwelling fish feeding on crustaceans, other invertebrates and fish. The females give birth to live young. Its lifestyle makes it vulnerable to trawling and other fishing methods, populations seem to be declining and it is subject to intensive fishing pressure, with its fins being sold into the Asian market. The International Union for Conservation of Nature has assessed its conservation status as being "critically endangered".

Description

The blackchin guitarfish is plain brown above and white below, and has a black blotch on its snout, more noticeable in juveniles than adult fish. It is similar in appearance to the common guitarfish (Rhinobatos rhinobatos) which is sympatric (shares the same range). Characteristic differences include the blackchin's smaller eyes, narrower rostral ridges (nearly united at the front), shorter front nasal lobe and narrower back nasal flap. Both species have short thorns present on the inner margins of the eye, on the shoulders and along the spine and tail, but these are less distinct in the blackchin.^[4] This species grows to a length of about 180 cm (71 in), although larger fish have been reported from Guinea in West Africa and the Gulf of Gabès in the southern Mediterranean.^[1]

Distribution

The blackchin guitarfish is found in eastern Atlantic Ocean between about 42°N and 17°S, 19°W and 36°E. Its northerly limit is the northern coast of Portugal and its southern limit is Angola. It is also found in southern and eastern Mediterranean Sea and has been recently recorded in the Black Sea.^[5] It lives on the continental shelf at depths down to about 100 m (330 ft).^[1]

Ecology

The blackchin guitarfish swims slowly over sandy and muddy stretches of seabed, foraging for shrimps, crabs, other crustaceans, squid and molluscs.^[1] Males reach sexual maturity at a length of about 150 cm (59 in) in Senegal, and females at about 163 cm (64 in), while in Tunisia the lengths at maturity are 100 cm (39 in) and 110 cm (43 in) respectively. This fish is ovoviviparous, the eggs being retained in the uterus of the female and the developing young being nourished first by a yolk sac, and later by uterine secretions.^[6] Litter size varies between about four and six in Senegal, but larger litters occur in Tunisia.^[1] The gestation period is between about five and eight months, there sometimes being a diapause in the embryo's development in colder-water months in Senegal, but no diapause seems to occur in Tunisia.^[6]

Status

The blackchin guitarfish is a low-fecundity fish and mature individuals aggregate off the coast seasonally to deliver their young and mate. At this time, they are particularly vulnerable to fishing activity. This species is particularly valued for its fins which sell at a high price, but the fish are also used for food. They are caught by trawling and gillnets in artisanal fisheries and as bycatch during industrial shrimp fishing. Along with the common guitarfish, they used to be plentiful in the northern Mediterranean and around the Balearic Islands, but seem to no longer be present in these areas. Catches off the coast of Africa have declined also, but data on landings is in short supply. The International Union for Conservation of Nature is concerned about the future of this fish and has assessed its conservation status as being "critically endangered".^[1]

References

^ ^a ^b ^c ^d ^e ^f ^g Kyne, P.M. & Jabado, R.W. (2019). "Glaucostegus cemiculus". IUCN Red List of Threatened Species. 2019: e.T104050689A104057239. doi:10.2305/IUCN.UK.2019-2.RLTS.T104050689A104057239.en. Retrieved 25 July 2019.
^ "Appendices | CITES". cites.org. Retrieved 2022-01-14.
^ Bailly, Nicolas (2015). "Rhinobatos cemiculus Geoffroy Saint-Hilaire, 1817". WoRMS. World Register of Marine Species. Retrieved 17 January 2016.
^ "Blackchin guitarfish (Rhinobates cemiculus)". Fishes of the NE Atlantic and the Mediterranean. Marine Species Identification Portal. Retrieved 17 January 2016.
^ Guide of Mediterranean Skates and Rays (Glaucostegus cemiculus). Oct. 2022. Mendez L., Bacquet A. and F. Briand.http://www.ciesm.org/Guide/skatesandrays/Glaucostegus-cemiculus
^ ^a ^b Seck, A.A; Diatta, Y.; Diop, M.; Guélorget, O.; Reynaud, C.; Capapé, C. (2004). "Observations on the reproductive biology of the blackchin guitarfish from the coast of Senegal". Scientia Gerundensis. 27: 19–30.