The discovery of cave-dwelling fish (and other cave organisms) is usually a rare event. Some of my colleagues have a very good explanation for this: The reason for sparse records of subterranean fishes might be related to the aridity of the area and the rarity of caves. While subterranean fishes are often called “cave fishes”, not all of them are strictly bound to caves. Entering caves is just the way humans approach the underground world and gain access to the macroscopic part of its biodiversity. This means that there is the possibility that many more troglomorphic organisms exist, which have never been observed by humans due to the lack of human-sized openings between the hypogean and epigean worlds.
However, sometimes we are lucky and find an exciting new species such as the new subterranean loach found in Iraqi Kurdistan. The species was named after Graham Proudlove (Manchester Museum, the University of Manchester), a world expert on subterranean fishes. The fishes were actually washed out from an aquifer and ended up in a small river. Here some footage - pretty exciting as it is obviously very rare to see these fishes under normal light conditions:
For the experts: Eidinemacheilus proudlovei, new species, is described from subterranean waters in the Little Zab River drainage in Iraqi Kurdistan. After the discovery of E. smithi in 1976, E. proudlovei is the second troglomorphic nemacheilid loach found in the Middle East and the second species placed in Eidinemacheilus. Eidinemacheilus proudlovei is distinguished from E. smithi by having 8+8 or 8+7 branched caudal-fin rays, no adipose keel on the caudal peduncle, enlarged jaws and a fully developed head canal system. It furthers differs substantially in its DNA barcode (>8% K2P distance) from all other nemacheilid loaches in the Middle East, Europe and Western India.