Nail rays
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Thorn rays ( Raja clavata ) |
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| Raja clavata | ||||||||||||
| Linnaeus , 1758 |
The nail skate ( Raja clavata ) is a cartilaginous fish of the family Skates and rays (Rajidae). It lives mainly on the European and African coasts of the Atlantic Ocean , in the North Sea , the Mediterranean and the southwestern Black Sea .
distribution
The spiked ray is the most common type of ray in the European seas. It lives on the coasts of the Eastern Atlantic from Norway to Namibia , in the North Sea , in the Skagerrak and in the Kattegat . Also in the Mediterranean , in the southwest Black Sea and possibly also in the extreme southwest of the Indian Ocean on the coast of South Africa , Mozambique and on the southern coast of Madagascar .
The nail-ray has become rare in German waters. While 18,000 smooth and nailed rays were still fished in East Frisia in 1910 , from 1980 onwards almost no nailed rays were sighted in the German Wadden Sea due to overfishing and bycatch. Their number has only increased again since 2010.
features
The body of the fish is rhombic, the snout short, the wing-like pectoral fins pointed. The upper side is spiked and rough, brown and patterned with light and dark spots, the underside white. The tail has two small dorsal fins far back and is provided with light and dark transverse bands. The central row of slender, nail-like thorns on the back and top of the tail is characteristic. Older animals get additional thorns on the top and bottom of the wings. The males reach a size of 70 centimeters, females are up to 120 centimeters long.
Way of life
Nail rays live on sandy and muddy soft bottoms at depths of 20 to 300 meters, in the eastern Ionian Sea at depths of 300 to 577 meters. They feed on bottom-dwelling invertebrates, mainly crustaceans , but also small fish.
Like all Rajidae , they are oviparous , i.e. they lay eggs. The mating season is in spring. The females lay an egg about every day a few weeks later, a total of 50 to 170 in a year. The eggs are encased by a square horn capsule with holding threads at each corner, five to nine centimeters long and 3.4 to 6.8 centimeters wide. After four to five months, the young hatch with a body length of about twelve centimeters.
literature
- Bent J. Muus, Jørgen G. Nielsen: The marine fish of Europe in the North Sea, Baltic Sea and Atlantic. Kosmos, Stuttgart 1999, ISBN 3-440-07804-3 .
- Hans A. Baensch , Robert A. Patzner: Mergus Sea Water Atlas Volume 6 Non-Perciformes (Non-Perciformes) , Mergus-Verlag, Melle, ISBN 3-88244-116-X .
Web links
- Spike rays on Fishbase.org (English)
- Raja clavata in the endangered Red List species the IUCN 2016 Posted by: Ellis, J., 2005. Accessed July 6, 2020th
- Video: Raja clavata - swimming movements . Institute for Scientific Film (IWF) 1959, made available by the Technical Information Library (TIB), doi : 10.3203 / IWF / E-189 .
- Crayfish (Raja clavata). In: WWF species dictionary. Retrieved July 6, 2020 .
Individual evidence
- ↑ A rare guest in the Wadden Sea: spotted rays. In: NDR 1 Lower Saxony. July 5, 2020, accessed July 6, 2020 .