The status of various fish species in the North Sea has only been tracked in a systematic way since 1970. Commercially fished species had already declined sharply by then. To analyze older data, the researchers had to fall back on various historical sources. These showed that the numbers of skate now being caught off the north coast of Scotland are notg even close to the numbers of the past. In the central and southern part of the North Sea there are still very few skates. That is one of the reasons the skate remains on the Red List of threatened species as ‘critically endangered’.
The flat, brown skate is a ray that lives at the bottom of the sea. With its mouth on the underside, it mainly catches shrimp. Prey was also the subject of the study. "From four hundred, somewhat smaller specimens from the NIOZ collection, we examined the stomach contents. We mainly found shrimp," Bom said, "although larger individuals are known to eat fish as well."
According to recent insights, 'the' skate actually consists of two different species: Dipturus intermedius, or blue skate and Dipturus batis, the flapper skate. In the North Sea, 'intermedius' is most common.
The decline of the skate in our waters most likely had to do with fishing, which targeted these large animals. Skates easily end up as bycatch in trawls as well. As trawl fishing becomes more strictly regulated, the skate gets a chance to return. "For such a large fish with slow reproduction, that return will take time," Bom knows. "But the tentative increase clearly shows that regulation of the fishery is helping to protect and hopefully one day allow vulnerable species to recover." Nowadays, it is illegal to land this endangered species. Fishermen who find a skate in their nets must put it back as quickly and carefully as possible.
Shifting baseline syndrome
Bom and van Leeuwen conducted their research at the request of the World Wildlife Fund, which wanted to know whether there is still room for iconic animals like the skate in the North Sea. The upward trend the researchers found is good news for conservationists. "But you certainly shouldn't cheer too soon," Bom believes. "We all suffer quite a bit from the shifting baseline syndrome. Everyone tends to look at the numbers from their own recent past, but then you easily forget that only a few decades before that, there were really a lot more skates around. Knowing that they mainly eat shrimp, and that there are still plenty of these in the North Sea, confirms the opportunities for these fish. There is still ecological potential for many more skates."
Method of Research
Subject of Research
A long-term view on recent changes in abundance of common skate complex in the North Sea
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