Since Friday, several news reports have been published in the Spanish and international press about the first sighting in surface waters of that country of a ‘black devilfish’, a rare marine species with a deformed body and somewhat frightening appearance, which lives in deep waters. The news widely disseminated by various media outlets states that although it has only just been detected in Spain, the species in question has been known to science for over a century and that the first sighting even took place in the sea off Madeira. Could this really have been the case?
According to the Spanish press, the fish in question was seen and filmed (see attached video) swimming for the first time in daylight, in shallow waters, on January 26, by a team of marine biologists from the non-governmental organization Condrik Tenerife, who were carrying out an expedition to study sharks and rays in the Canary Islands.
Its scientific name is ‘Melanocetus johnsonii’, but it is known in Spain as ‘black devil’. In Madeira, particularly among fishermen in Câmara de Lobos, this species and others similar to it are generically called ‘deepwater frogs’. “They are fish that are somewhat related to the monkfish, but they are obviously from a very distinct family. They live in very deep waters. Fishermen call them ‘deepwater frogs’ because they have that rounded shape”, explains Manuel Biscoito, ichthyologist (specialist in the study of fish) and head of the Science Division of the Funchal City Council.
The Madeiran researcher says that these fish have an interesting characteristic that can be seen in the video captured at the end of January in the Canary Islands. The females exhibit very significant sexual dimorphism. The first ray of the dorsal fin is modified and has the shape of a luminous organ at the tip, which the fish uses to attract prey. Normally, the males are much smaller and live ‘attached’ to the females and no longer have an independent life. Sometimes, the female carries one or more males, which facilitates reproduction in the deep sea.
Despite their frightening appearance, these fish pose no threat to humans. First of all, because they live at depths of 1,000 or 2,000 metres and “under normal circumstances have no contact” with people. On the other hand, this is a relatively small species – females measure up to 18 centimetres and males three centimetres – so they do not cause any problems, despite having a large mouth and well-developed teeth. This last characteristic is common to other species in the same marine environment, such as the black scabbardfish. “Since there is a scarcity of food at these depths, many deep-water fish tend to develop very powerful teeth, to be able to grab their prey and not let it escape”, explains Manuel Biscoito.
The same biologist states that, despite having only now been filmed on the surface, this “is a fish already known” to Madeiran fishermen, particularly those who fish for swordfish, which also lives at great depths. “It may not be as rare as that. Our instruments are simply not suitable for collecting this type of specimen”, says Manuel Biscoito. One of the hypotheses to explain its coming to the surface of the sea is that it generated gases during the digestion process, after ingesting prey. As this is not its natural habitat, this species normally does not survive when it reaches the shallow sea. This is what happened with the fish filmed in the Canary Islands on 26 January.
Finally, the expert confirms that the ‘Melanocetus johnsonii’ had its first scientific description from a specimen captured in the sea of Madeira on December 24, 1863. The discovery was the responsibility of ichthyologist Albert Günther, from the Natural History Museum in London. The scientific name is dedicated to James Yate Johnson, a naturalist who was in Madeira in the 19th century.
In the scientific collection of the Natural History Museum of Funchal there are “at least 18 specimens” of this species, which were collected over the years. The oldest was collected in 1953 and the most recent in 2006.