The blackchin guitarfish (''Glaucostegus cemiculus'', formerly ''Rhinobatos cemiculus'') is a species of cartilaginous

fish A fish (: fish or fishes) is an aquatic animal, aquatic, Anamniotes, anamniotic, gill-bearing vertebrate animal with swimming fish fin, fins and craniate, a hard skull, but lacking limb (anatomy), limbs with digit (anatomy), digits. Fish can ...

in the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Rhinobatidae. It is native to the eastern Atlantic Ocean and the Mediterranean Sea. It is a bottom-dwelling fish feeding on

crustacean Crustaceans (from Latin meaning: "those with shells" or "crusted ones") are invertebrate animals that constitute one group of arthropods that are traditionally a part of the subphylum Crustacea (), a large, diverse group of mainly aquatic arthrop ...

s, other

invertebrate Invertebrates are animals that neither develop nor retain a vertebral column (commonly known as a ''spine'' or ''backbone''), which evolved from the notochord. It is a paraphyletic grouping including all animals excluding the chordata, chordate s ...

s 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 The International Union for Conservation of Nature (IUCN) is an international organization working in the field of nature conservation and sustainable use of natural resources. Founded in 1948, IUCN has become the global authority on the stat ...

has assessed its conservation status as being "

critically endangered An IUCN Red List critically endangered (CR or sometimes CE) species is one that has been categorized by the International Union for Conservation of Nature as facing an extremely high risk of extinction in the wild. As of December 2023, of t ...

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 In biology, two closely related species or populations are considered sympatric when they exist in the same geographic area and thus frequently encounter each other. An initially interbreeding population that splits into two or more distinct spe ...

(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. This species grows to a length of about , although larger fish have been reported from

Guinea Guinea, officially the Republic of Guinea, is a coastal country in West Africa. It borders the Atlantic Ocean to the west, Guinea-Bissau to the northwest, Senegal to the north, Mali to the northeast, Côte d'Ivoire to the southeast, and Sier ...

in West Africa and the

Gulf of Gabès The Gulf of Gabes (or Cabès, Cabes, Gaps; ), also known as Lesser Syrtis (from ; ), contrasting with the Greater Syrtis in Libya, is a gulf on Tunisia's east coast in the Mediterranean Sea, off North Africa. The gulf roughly spans the coast from ...

in the southern Mediterranean.

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.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 It lives on the continental shelf at depths down to about .

Ecology

The blackchin guitarfish swims slowly over sandy and muddy stretches of seabed, foraging for

shrimp A shrimp (: shrimp (American English, US) or shrimps (British English, UK)) is a crustacean with an elongated body and a primarily Aquatic locomotion, swimming mode of locomotion – typically Decapods belonging to the Caridea or Dendrobranchi ...

crab Crabs are decapod crustaceans of the infraorder Brachyura (meaning "short tailed" in Greek language, Greek), which typically have a very short projecting tail-like abdomen#Arthropoda, abdomen, usually hidden entirely under the Thorax (arthropo ...

s, other

squid A squid (: squid) is a mollusc with an elongated soft body, large eyes, eight cephalopod limb, arms, and two tentacles in the orders Myopsida, Oegopsida, and Bathyteuthida (though many other molluscs within the broader Neocoleoidea are also ...

and

molluscs Mollusca is a phylum of protostome, protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant taxon, extant species of molluscs are recognized, making it the second-largest animal phylum ...

. Males reach sexual maturity at a length of about in Senegal, and females at about , while in Tunisia the lengths at maturity are and respectively. This fish is

ovoviviparous Ovoviviparity, ovovivipary, ovivipary, or aplacental viviparity is a "bridging" form of reproduction between egg-laying oviparity, oviparous and live-bearing viviparity, viviparous reproduction. Ovoviviparous animals possess embryos that develo ...

, 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. Litter size varies between about four and six in Senegal, but larger litters occur in Tunisia. The gestation period is between about five and eight months, there sometimes being a

diapause In animal dormancy, diapause is the delay in development in response to regular and recurring periods of adverse environmental conditions.Tauber, M.J., Tauber, C.A., Masaki, S. (1986) ''Seasonal Adaptations of Insects''. Oxford University Press It ...

in the embryo's development in colder-water months in Senegal, but no diapause seems to occur in Tunisia.

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 Bycatch (or by-catch), in the fishing industry, is a fish or other marine species that is caught unintentionally while fishing for specific species or sizes of wildlife. Bycatch is either the wrong species, the wrong sex, or is undersized or juve ...

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

is concerned about the future of this fish and has assessed its conservation status as being "

References

{{Taxonbar, from=Q3024679 blackchin guitarfish Fish of the Atlantic Ocean Fish of the Mediterranean Sea blackchin guitarfish