Together with a European team, researchers from Senckenberg am Meer in Wilhelmshaven have described a new species of fish. Gaidropsarus mauritanicus is only about 73 millimeters long and lives in the deep-sea coral reefs off the coast of Mauritania.

In her now in Journal of Fish BiologyThe scientists explain that the fish from the sea bass family has probably remained undiscovered until now due to its small size and its protective behavior.

Over a quarter of the world’s commercially caught marine fish belong to the cod family. Cod, Alaska pollock and haddock are of particular economic importance.

“The order Gadiformes also includes much smaller, mostly unknown and little-researched fish families, such as the klipfish (Gaidropsaridae), which have little commercial value but are remarkably widespread,” explains Alexander Knorrn from Senckenberg am Meer in Wilhelmshaven.

Together with Senckenberg researchers and colleagues from Portugal and Spain, Knorrn described a new species from the sea bass family as part of his doctoral thesis. The fish, which is around 73 millimeters long and is now considered the holotype of the species, was first observed and collected off the coast of Mauritania at a depth of 595 meters. This is where the world’s largest deep-sea coral reef complex, the “Mauritanian Wall,” is located, which stretches for at least 580 kilometers and is between 80 and 100 meters high.

“The fish species was also observed during eight dives with remote-controlled vehicles along the Mauritanian coast at depths between 613 and 416 metres,” adds the Wilhelmshaven researcher.

The new fish species could be distinguished from its conspecifics by a combination of different characteristics – including the large eyes and the head, which takes up a quarter of the animal’s body length, elongated pelvic fins and the pink coloring. Genetic analyses confirm that it is a previously undescribed species. “This is remarkable because new vertebrate species are quite rare,” says Knorrn.

The small fish was caught using a gripper, together with a variety of living deep-sea animals, including corals such as the scaffold-forming stony coral Desmophyllum pertusum or the red deep-sea gorgonian Swiftia phaeton, but also larger sponge colonies, bryozoans, brittle stars, annelids, decapods, snails and mussels.

“The video recordings also show that Gaidropsarus mauritanicus lives exclusively in deep-sea coral ecosystems,” adds Knorrn. “One of the specimens we observed had whitish patches on its skin. It was the only fish we observed seeking shelter under a branched, whitish bryozoan, Celleporina cf. lucida.”

The research team cites this suspected territorial behavior, coupled with a more protective behavior and the small body size of the animals, as the reason why the deep-sea species has remained undiscovered so far.

Coral reefs in the deep and cold regions of the world’s oceans are of enormous importance as nurseries, breeding centers and hunting grounds for predators. Numerous organisms such as fish, crabs, mussels, sponges and snails find protection and food in their calcareous skeletons.

The reefs also serve as CO₂ Reservoirs. But deep-sea corals are at risk: oxygen deficiency and ocean acidification threaten the reefs. Intensive trawling also puts deep-sea corals under great pressure.

“With the name Gaidropsarus mauritanicus, we want to emphasize that Mauritania has a unique and enormously species-rich marine ecosystem that urgently needs to be protected,” explains Prof. Dr. André Freiwald, Head of Marine Research at Senckenberg am Meer.