- Dut: Stekelrog (Doornrog, Driestaart, Rode rog)
- Lat: Raja clavata
- Eng: Roker (Thornback ray)
- Ger: Nagelrochen
- Dan: Sømrokke
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- Thornback ray (roker), Ecomare
Thornback ray
The thornback ray owes its name to the numerous spines on its back and tail. It lives on sandy, muddy and pebbly bottoms sea bottoms and hunts mostly at night. It can live to 20 years old. The females grow to 1.25 meters in length; the males rarely grow longer than 70 centimeters. Adult thornback rays have 36 to 44 rows of teeth and eat worms, small crustaceans, small sea snails and small benthic fish. They do not reproduce until a later age, which is why they are threatened by the demersal fisheries.
- Adulthood
- Egg capsule of the thornback ray, Ecomare
Female thornback rays are sexually mature between nine and twelve years old, males between seven and twelve years. This means there is a good chance that the thornback ray is caught (while fishing for flatfish with a beam trawler) before it is able to reproduce. The eggs are laid in the spring. After four to five months, the narrow end between the protrusions breaks open and the barely twelve centimeter-long thornback ray crawls out of the egg. The protrusions serve to attach the egg capsule to a hard surface as well as to provide oxygen for the embryo.
- Distribution of the thornback ray
- Distribution of the thornback ray., Ecomare
Thornback rays used to be very common in the North Sea, even along the coast and in the Wadden Sea. Around 1900, thronback rays were the most common ray species in the southern North Seal In those days, thornback rays were purposely fished from Den Helder. Around 1960, the ray disappeared from the Wadden Sea and by 1970, from the delta and coastal waters. Presently they are rarely found in the coastal waters and tidal regions, although in the summer of 2000, young thornback rays were reported several times off the Dutch coast. It appears that the thornback ray is starting to establish itself in the (more southern) rocky areas of the sea floor, where one hardly ever fishes for other benthic fish. Thornbacks are still found along the English side of the North Sea. The International Council for Exploration of the Seas (ICES) advised closing this area for fishing.
- Environmental indicator
