The 1970 trawl that produced the record specimen brought up a small pale ophidiid from 8,370 metres. It remains the deepest recorded capture of a fish, although the animal was dead when it reached the surface, and the record is sometimes qualified on the ground that a trawl samples a range of depths as it is hauled.
Cusk-eels are otherwise remarkable for their range. Ophidiidae includes species living in shallow coastal water and in caves, alongside deep bathyal and hadal forms, so a single family spans nearly the full vertical extent of fish life.
Many cusk-eels are also noisy. Several genera have specialised sonic muscles attached to the swim bladder and produce pulsed sounds, and in some species the sound-producing apparatus differs between males and females. The best-studied cases concern the shallower species, where recordings are easier to obtain than in the trenches.