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 which is sympatric. Characteristic differences include the blackchin's smaller eyes, narrower rostral ridges, 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 in West Africa and the Gulf of Gabès in the southern Mediterranean.
Distribution
The blackchin guitarfish is found in the warm temperate and tropical waters of the Mediterranean Sea and the 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. Its range in the Mediterranean Sea it mostly concentrated in the southern and eastern parts. 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 shrimps, crabs, other crustaceans, squid and molluscs. 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, 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 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 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".
