Blackchin guitarfish
| Blackchin guitarfish | |
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| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Chondrichthyes |
| Order: | Rajiformes |
| Family: | Rhinobatidae |
| Genus: | Rhinobatos |
| Species: | R. cemiculus |
| Binomial name | |
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Rhinobatos cemiculus Geoffroy Saint-Hilaire, 1817 |
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The blackchin guitarfish (Rhinobatos cemiculus or sometimes Glaucostegus cemiculus) 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 "endangered".
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. 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.
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 100 m (330 ft).
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 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. 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.
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Wikipedia