Thornback Ray

The thornback ray is a cartilaginous fish that prefers to dwell on the sea floor, either in deeper water or along the coast. Its alternate name, the thornback skate, is more accurate, given that this fish is actually a skate, not a ray. It lives in the Atlantic and Indian Oceans, mostly along European and West African coastlines. This skate is a popular sport fish with anglers, though many choose to catch and release it due to its conservation status.

Thornback Ray Fish Facts

• Related to sharks: This species is closely related to sharks, having diverged from them about 200 million years ago. In fact, some shark species are closer to rays and skates than to other sharks.
• Spines, not stingers: Thornback rays are actually skates, which means they have spines on their backs instead of stingers on their tails.
• Powerful jaws: Their mouths don’t look all that fearsome, but they pack a mean bite. Their teeth are also extremely sharp.
• Good eating: Even though the IUCN lists this species as Near Threatened, many people still enjoy eating its lean meat.
• Bottom-dwelling: This fish likes to hang out on the sea floor, disguising itself among the sediment. Because the species is nocturnal, it usually burrows into the sand or mud during the day and comes out at night to cruise around for food.

Evolution and History

Thornback rays and other members of the Rajiformes order have left behind relatively little evidence of their evolutionary history. This is due to their cartilaginous skeletons, which are softer than bone and therefore do not easily fossilize. Northern Africa and southern Europe have yielded the majority of the earliest fossils, mostly in the form of teeth and scales.

The available evidence suggests that the thornback ray’s ancestors date back to the Lower Jurassic, 150 million years ago, though they most likely began to split off from sharks as far back as 200 million years. Most of the current taxonomical groupings appear to have developed from the Upper Cretaceous, 100 million years ago, to the Paleocene, 50 million years ago. Some scientists speculate that rays and skates have experienced greater speciation (diversity) than sharks due to the more diverse range of benthic (sea floor) environments. Strangely enough, some shark species remain more closely related to rays and skates than to other sharks.

The phylogenetic development of the thornback ray is uncertain, though scientists have studied European populations to measure their diversity. They found that populations in the Mediterranean, Adriatic, and Black Seas all shared a single mitochondrial haplotype, which is a region of DNA that helps to show maternal lineages. British populations, however, had a second mitochondrial haplotype that differentiated them from some other European populations. Evidence suggests that thornback ray numbers expanded significantly between 580,000 and 362,000 years ago.

Classification and Scientific Name

The scientific name for the thornback ray is Raja clavata. Alternate names for this fish include thornback skate, maiden ray, and rough ray. Although its common name includes the word “ray,” it is technically a skate. Among other differences, rays have stingers on their tails while skates typically have spines on their backs.

The thornback ray belongs to the class Chondrichthyes, which comprises cartilaginous fishes. These fish primarily have cartilage instead of bone. Its subclass, Elasmobranchii, includes sharks, rays, skates, and sawfish. It further belongs to the order Rajiformes (over 500 species of rays and skates), the family Rajidae (over 200 species of skates), and the genus Raja (16 species of skates).

Appearance

The thornback ray is flat and kite-shaped with distinctive wings ending in points. It uses these wings to move underwater. Its tail is long and fleshy, but like the tails of all other skates, it lacks a stinger. It may, however, have spines. The dorsum is prickly, though large females may also have spines on their ventral region. Juveniles and large males may have spines along the bottoms of their snouts and the edges of their discs. Adults often have “bucklers” (button-like growths) at the bases of their disc spines.

In all individuals, the dorsum is brownish or greyish with brown or grey spots. The underbelly is white, fading to grey at the edges. Though this species has a small downward-facing mouth, its jaws are powerful. Two nostrils just above the mouth are sometimes mistaken for eyes. The rostrum (snout) is rounded.

Male thornback rays grow up to 41 inches in length, while females are somewhat larger, up to 55 inches in length. However, the average length for this species is 33.5 inches. Disc width (width from wingtip to wingtip) for adults is a minimum of 15 inches. The largest individual on record weighed just under 40 pounds.

Distribution, Population, and Habitat

Thornback rays thrive in marine environments, typically coastal waters. Though they are saltwater fish, they are capable of surviving in lower salinity. They are also demersal, meaning they tend to lurk along the sea floor. This species inhabits areas of the Atlantic and Southwest Indian Oceans, notably along the coasts of Europe and West and South Africa. It also lives in the Mediterranean and Black Seas.

These fish prefer to live at a depth of approximately 30 to 100 feet, though scientists have discovered some individuals at depths of nearly 3,350 feet. They often camouflage themselves in sediments on the ocean floor, like mud, sand, and gravel, especially during the day. Their coloration makes it easy for them to blend in.

Conservationists do not know the exact number of thornback rays in the world, but they believe that their populations are declining. For this reason, the IUCN lists this species as Near Threatened.

Predators and Prey

Thornback rays are carnivorous, opportunistic feeders that survive by camouflaging themselves on the ocean floor. As nocturnal animals, they are usually active at night and rest during the day. Their favored method of hunting is to grab prey as it swims by or as it rests on the seabed. Despite their ability to hide, they have several natural predators besides humans.

What Do Thornback Rays Eat?

Thornback rays, both adults and juveniles, eat crustaceans like amphipods, shrimp, and crabs. Fully grown individuals also enjoy sand eels and other small fish. Because of their powerful jaws and sharp teeth, they are able to crack the hard outer shells of crustaceans.

What Eats Thornback Rays?

Humans are one of the primary predators of the thornback ray. Other potential threats include seals and shark species like angel sharks and bluntnose sixgill sharks. Some fish, like the Atlantic cod or grey gurnard, also prey on this species.

Reproduction and Lifespan

Thornback rays prefer deeper waters in winter, but when temperatures rise, they move to shallower waters to breed. Females typically migrate a month before the males, who follow afterward. Their breeding season lasts from February to September, though June sees the most activity. The polyandrous females usually mate with more than one male.

This species is oviparous, meaning it lays eggs that then develop and hatch outside the mother’s body. It is also characterized by single oviparity, which means each egg contains only one embryo. The eggs are oval and pointed at both ends. Females usually only lay once or twice a year, producing up to 170 eggs annually, though the average number is 48-74.

Females lay their eggs in winter, spring, or summer, depositing them in the sediment on the sea floor. The eggs hatch after four to five months. The newly hatched pups are between 4.3 and 5.1 inches long. They survive by feeding on the yolk from the eggs. Sexual maturity occurs at about seven to eight years of age, usually sooner for males than females. The maximum lifespan for this species is 15 years.

Thornback Ray in Fishing and Cooking

It is legal in most places to fish for thornback rays, both recreationally and commercially. Though it may come as a surprise to many, some people enjoy eating this fish.

Fishing

The best time to fish for this fish near shore is from May to September, though they move inland as early as February. After September, they return to deeper waters. Anglers are likely to find these fish swimming in areas with sediments like sand, mud, or gravel. Rocky or rough ground is unlikely to harbor this species.

The best bait for thornback rays is whole small fish like sprats, though parts of larger fish like mackerel, herring, or pilchard may also generate good results. Fishermen can also try using bait like sand eels, worms, and crustaceans. Anyone attempting to handle this fish after catching it should exercise caution, as both its teeth and its spines are sharp.

Commercial fisheries also fish for this species in various areas like the Irish and Celtic Seas, the eastern English Channel, the North Sea, Skagerrak, and Kattegat. Methods of catching this fish include seines, otter trawls, bottom trawls, and trammel nets. According to the Southern IFCA, 260 tonnes of fish were landed from relevant ICES areas in 2021, though this figure includes multiple species and not just thornback ray.

Cooking and Eating

Thornback rays are good for eating with several acceptable preparation methods, including frying, baking, or sautéing. With lean meat like this, it’s best to prepare it with oil or sauce. The UK’s The Telegraph featured this recipe for thornback ray with cockles and brown butter. BBC Good Food recommends preparing this fish with buttery parsley and capers. For those interested in a more comprehensive experience, this guide shows readers how to catch, skin, and cook this unique fish.

Because its meat is so lean, this species is an excellent choice for people watching their fat intake. 100 grams of thornback ray meat contains about 68 calories, 14.2 grams of protein, 0.9 grams of fat, and 0.7 grams of carbohydrate.