The common skate is one of the large predatory fish in the North Sea. But what kind of fish are they? Much is still unknown about the animals, and photos of this Red Listed species are extremely rare. But this summer, marine biologists from Queen’s University Belfast managed to lure the animals on camera with bait. As ARK Nature Development’s North Sea team supports this research, we are allowed to preview their video from the waters around the Orkney Islands in Scotland. This is where these giant rays lay their huge eggs.
Skating in front of the camera (Source: ARK Nature Development & Queen’s University Belfast)
“What amazing animals,” says Ernest Shriver, ARK field worker and marine ecologist, as he collects the material. “They don’t care about anything. True top predators. These are I think six feet tall, flipper to flipper. And they can get a lot bigger than that.”
The common skate is a brown, cartilaginous fish with a large, flat, somewhat diamond-shaped tail. The fish, which matures slowly, can live up to eighty years, eventually growing to three metres, breeding in limited numbers and depositing eggs in a ‘mermaid bag’ – of A4 size – which takes up to two years. out. With their mouths on the underside of the body, they eat fish, shellfish, and crustaceans from the bottom.
There are two types in the North Sea: Diptaurus intermedius And the Diptaurus batis. They do not yet have a separate name in Dutch. They are called in English ski flap And the Combined skiing or Blues.
The recovery is hesitant
Skates are curious in nature and therefore easy to catch. This could lead to their extinction. In the last fifteen years the common skate appears to be making a somewhat recovery in the North Sea, though only in the northern part. This is evident from research published this month. “We now find about 1.7 skis per square kilometer surveyed per survey. Five years ago that was one ski per square kilometer, ten years ago we found one ski per about three square kilometers. It’s a huge improvement in percentages, but we’re still talking Their numbers are very low compared to what the historical sources say,” says researcher Roiland Bohm of the Netherlands Institute for Marine Research.
This is not certain, but it is possible that the skates observed in the north laid their eggs along the rocky Scottish coasts where the above images were also made. From there the animals can flock. “They swim four hundred kilometers from where they are now pictured to the Dutch part of the Dogger Bank. They will only be able to cover that distance if they find enough food on the sea floor,” Shriver says. Perhaps in time, the basalt blocks on the foundations of windmills could also be made suitable as “rocks” for laying eggs.
Predators are part of a healthy ecosystem
Healthy, rich ecosystems require large predators. They keep the numbers of small predators in check, and their presence alone adds variety to the landscape. Their prey animals become fearful and less common in their habitat. For example, a deer that grazes on the river bank all day, and becomes more alert when a wolf lurks in the bushes. They eat shorter, closer together, and more often in the same spot where they have a good view of danger. The young tree can now grow large in the river where birds can nest. Leaves fall into the river, the bird in it gets out, aquatic life benefits, and so the wolf has contributed to creating a more diverse natural environment and ecosystem without hunting a single deer.
This “scene of fear” principle also seems to work in the North Sea. Sea wolves – literally and figuratively like adult cod and old bass – are ferocious hunters, just like sharks and rays. Sturgeons given a life span can reach 12 feet and they don’t do this on a diet of sea lettuce. Marine mammals are not vegetarians either. The harbor porpoise, harbor seal, gray seal, and the occasional orca—all have their part in keeping small predators in check and directing prey behavior with their presence. For example, rays eat starfish and sea urchins eat shellfish. So oyster reefs can expand more easily if rays live nearby.
Large, long-lived predatory fish are good indicators of a healthy sea. When it blooms, you know the marine ecosystem is healthy.
Text: Iris Rugima, ARK Nature Development
Images: QUB School of Biological Sciences & Fjordstrong Ltd
Film: ARK Nature Development and QUB School of Biological Sciences