Deepest cusk eel

The greatest depth at which a cusk eel has been filmed in situ is 7,176 m (25,543 ft), for an unknown species of Bassozetus (a group sometimes known as assfish) in the Java Trench (aka Sunda Trench) in the eastern Indian Ocean. The data was published in Deep-Sea Research I in December 2021.

True eels belong to the order Anguilliformes. Cusk eels (order Ophidiiformes) are not true eels, although they have an eel-like appearance.

Another cusk eel, Abyssobrotula galatheae, was once widely regarded as not just the deepest of its kind but the deepest fish of any type, with one reportedly collected from a depth of 8,370 m (27,460 ft) in the Puerto Rico Trench in the Atlantic Ocean. This is now disputed, however, as its collection was not observed/recorded so it may conceivably have been dredged at a shallower region in the water column.

The current undisputed fish to dwell at the greatest depth are the snailfish (Liparidae), several species of which have been filmed in excess of 8,100 m (26,575 ft) in the ocean's hadal zone.