Extinction by overfishing ... thanks to an 80-year-old mistake

An 80-year-old mistake could lead to the first extinction of a marine fish species by commercial fishing, new research has found.

The European common skate, long classified as Dipturus batis, has been on the World Conservation Union’s Red List of Threatened Species since 2006. However, new research reveals that the one species is actually two: the flapper skate, or Dipturus intermedia, and the blue skate, or Dipturus flossada. In fact, scientists knew that in the mid-19th century, but adopted the single classification based on the assertions of a single researcher in 1926.

While both species are today endangered, the fact that they were lumped into a single classification means the depletion of the flapper skate — the more endangered of the two — has been masked in the catch record. As a result, the flapper skate faces a far higher risk of extinction than previously thought.

“The threat of extinction for European Dipturus together with mislabelling in fishery statistics highlight the need for a huge reassessment of population for the different Dipturus species in European waters,” said researcher Samuel Iglésias. “Without revision and recognition of its distinct status the world’s largest skate, D. cf. intermedia, could soon be rendered extinct.”

Iglésias launched his study after noticing significant differences in the common skate specimens he saw in fish markets.

“I estimated at the beginning that it would take some weeks to resolve this question, but in the end it took me about two years,” he said.

Once abundant in British and European waters, common skates have been in sharp decline for decades. As of 2008, the International Council for the Exploration of the Sea has advised no target fishing for the skate, along with a recommendation for minimising by-catch.