What lies beneath Iraq’s desert? A river filled with rare blind fish

Iraq: Iraqi environmental police have documented an underground river inhabited by rare blind fish deep beneath the desert of Anbar province, in an unusual environmental and geological discovery.

The site lies at Al Khasfa, a deep geological depression and cave formation near Haditha in western Iraq. Footage released by Iraq’s Ministry of Interior showed members of the environmental police descending into the formation to investigate the subterranean ecosystem.

The team descended more than 500 metres in difficult conditions, including low oxygen levels, before reaching an underground water passage linked to the upper Euphrates river system, according to the ministry and researchers involved in documenting the site.

Dr Omar Al Sheikhly, an environmental scientist with the Green Climate Organisation, said Al Khasfa is part of an extensive cave system beneath the desert. The underground water system is believed to extend for more than 130 kilometres eastwards from the Euphrates.

Reaching the flowing underground river requires travelling deep into the geological formation, with the wider route described by researchers as extending for nearly two kilometres.

But it was what researchers found in the water that attracted particular attention.

Large numbers of rare fish were observed living in permanent darkness without functional eyes. The fish survive in an environment radically different from surface waters, feeding on bacteria and fragments of dissolved organic material, according to the team.

The fish, known locally as the Haditha blind fish, are highly specialised freshwater species adapted to life underground. Their bodies can appear translucent or pale pink because of the absence of pigmentation associated with prolonged life without sunlight, making some of their internal organs visible.

Researchers attribute such characteristics to generations of adaptation to complete darkness. Eyes provide little advantage in a lightless environment, while other sensory mechanisms become increasingly important.

The fish instead rely heavily on touch and their lateral-line sensory system, which allows them to detect subtle vibrations and changes in water pressure and navigate without sight.

Researchers said two principal types had been documented, with the possibility of a third. Some specimens observed at the newly documented location were also larger than measurements previously recorded.

Blind fish in the area were first documented in 1955. The latest expedition, however, found them at a new location, in greater numbers and at greater sizes than at the original discovery sites. The Interior Ministry described the scale and characteristics of the finding as the first documented discovery of its kind in Iraq and the wider Middle East.

The fish are considered threatened species and are included on the International Union for Conservation of Nature’s Red List, according to the researchers.

Video of the expedition quickly attracted attention on Iraqi social media. Some residents of the area pointed out that Al Khasfa itself has been known to local communities for decades and is part of the region’s familiar geography.