With his body flattened and its thin tail, the morphology of the ray has adapted perfectly to life in the seabed. Meeting with a descendant of shark.
Line identity card
The rays or batoids form a superorder of fish cartilaginous containing nearly 500 species divided into 13 families, the most famous representatives of which are sharks. The family of rajids counts more than 650 species such as the curly ray, the flowered ray and the soft ray which frequent for example the waters of Brittany and Normandy. However, rays should not be confused with the species grouped together under the denomination of “flat fish”Like sole or plaice because they are unrelated. Namely that all the rajids do not include the term “ray” in their vernacular name, it is in particular the case of the pouches.
Description of the line
Stingrays are distinguished by their body flattened, large wing-shaped pectoral fins, ventral gill slits and no anal fin. Batoids can take an oval, round or triangular and their dresses and sizes vary by species. The eyes are on the top of the head as well as the stigmata by which the rays breathe by sucking the water which they then expel through the gills. Some species, such as the stingray, have a dart whose bites are often painful, even fatal for humans. In the curly ray, the female can measure up to 1.20 m long while the male reaches only 70 cm, like the star ray. As for the giant manta ray, it can reach 8 m in length and weigh up to 2 tons, which makes it the largest ray in the world.
Rather active at night, this carnivore swims on the seabed and grazes the sand to pick up the prey buried in the sediment. Since most rays have developed large rounded teeth, they are able to break through shells benthic species such as gastropods, clams, oysters, crustaceans. Batoid also consumes lugworms, starfish and especially flat fish, such as sole or plaice. Only the manta ray feeds on plankton by filtering the water with its gills and the shrimp, krill, crab and other microscopic animals sucked in at the same time.
Skate distribution and habitat
The rajids live in fresh water or at sea. Most batoids are fond of tropical and subtropical marine environments, but some species also frequent these areas. temperate and cold. Thus, we meet stingrays in the waters french of the North-East Atlantic, the English Channel, the North Sea. A few species range from Norway to the African coasts and the Mediterranean. The manta ray lives mostly in the Pacific Ocean, Atlantic Ocean and Indo-Pacific Basin. The funds of sand, pebbles and pebbles constitute the privileged haunts of these fish. If the rajids prefer to evolve in the waters coastal up to 100 meters deep, others go down to 3000 meters.
In rajids, some species are oviparous, like the curly ray, that is, the eggs hatch outside the female’s body. Other species (eagle ray, manta ray) are ovoviviparous : their eggs hatch in the female’s uterus where the embryos continue to develop. Each egg is then contained in a capsule (oothèque) very resistant commonly called mermaid purse. After a few months, the young fish come out of their eggs that are often found on beaches in the form of empty shells. This method of reproduction protects the young and releases them into the environment at a more advanced stage of development. However, the low fertility rays make them very vulnerable to fishing activity.
Threats to the ray
The overfishing combined with a low fertility rate, a third of the ray population is at risk of extinction. Thus, 26% of species from the North Atlantic and 42% from the Mediterranean appear on the red list of species in danger of extinction established by the International Union for the Conservation of Nature (IUCN). For example: the curly ray is classified as “near threatened” and the manta ray “vulnerable”; At the professional fishermen, the stocks of brown skate (except the Channel brown), western British Isles white skate and North Sea and western British Isles gray skates are considered to be exhausted. In the North-East Atlantic, with the exception of the curly and gentle rays, all the other species show a worrying situation. The longevity of the rajids varies according to the species: from 14 years for the flowered ray to 20 years for the manta ray.