Using a remote lander* with a camera, a UK-Japan team has set a record for filming the deepest fish. The fish is Pseudoliparis amblystomopsis, a deep-water snailfish, found so far only in the Northwest Pacific. The species was described in 1955 by a Russian scientist with the holotype described from 7.2km. The depth range is extremely deep, from 6.1km to 7.5km deep. The film taken by the joint team actually contains a group of 17.
The deepest record for any fish is Abyssobrotula galatheae, a cusk eel, known from depths of 3.1-8.4km. This species was only described in 1977. The deepest specimen is known form the Puerto Rico Trench but is likely to have a global distribution.
The deepest record of any fish spotted live is debatable but probably around 7km and this new record is a definite contender.
* A remote lander is an instrument pack that is deployed on the ocean floor. They are not tethered to the surface and for all practical purposes have no direct communication to the surface while on the floor. The lander ususally posses an array of instruments to measure temperature, conductivity, salinity, oxygen, and currents as well as either a time-lapse or continuous frame camera. Usually the cameras are tripped by either a motion detector or baited hook. Sonar is used to trigger the lander to release its weights and return to the surface.