Deepest fish (Observed)

Last updated: January 9, 2020 at 3:28 am

The Swire’s snailfish (Pseudoliparis swirei) was captured on video at the depth of 8,178 m (26,831 ft) in 2017. This species, more commonly referred to as the Mariana snailfish, was discovered in 2014.

A cusk-eel (Abyssobrotula galatheae) was reportedly collected at the depth of 8,370 m (27,461 ft) in 1970. The record depth is subject to debate since the fish may have been caught with a non-closing net, i.e. it may have been captured in the water column while the net was being lowered or raised.

Dr. Jacques Piccard reported observing a sole-like fish on the seafloor during his record submersible descent in the Challenger Deep (10,916 m | 35,814 ft) with Don Walsh in 1960.

“Lying on the bottom just beneath us was some type of flatfish, resembling a sole, about 30 cm (1 ft) long and 15 cm (6 in.) across. Even as I saw him, his two round eyes on top of his head… here apparently, was a true, bony teleost fish, not a primitive ray or elasmobranch… slowly, this flatfish swam away.” — From: Seven Miles Down: The Story of the Bathyscaphe Trieste (1961) by J. Piccard and R. S. Dietz. pp. 172-174. Published by the Putnam, New York.

This account has since been dispelled by several scientists based on a number of factors, including the mismatch of depths compared with fish of similar body form, the total absence of any fish filmed by cameras in the same area and at similar depths, and a new hypothesis whereby fish would be physiologically incapable of surviving at depths greater than 8,500 m (27,887 ft) (Jamieson and Yancey, 2012).

“Just before we landed we spotted what appeared to be a small, whitish flatfish resting on the seafloor. We judged it about a foot long. Jacques was at the window and made the sighting. […] In the half century since our dive, there has been some speculation that we did not see a flatfish. And this is entirely possible. Neither Jacques nor I were trained biologists and the critter could have been something else.” — Don Walsh (Burton, A. 2012)

The ‘fish’ observed by Piccard may have in fact been a large sea cucumber, Galatheathuria aspera, which is white, oval, and about a foot long (Jamieson and Yancey, 2012).

Alan J. Jamieson and Paul H. Yancey, On the Validity of the Trieste Flatfish: Dispelling the Myth, The Biological Bulletin 222, no. 3 (June 2012): 171-175.
Wolff, T. 1961. The deepest recorded fishes. Nature 190: 283– 284.
Burton, A. 2012. Way down deep. Front. Ecol. Environ. 10: 112.
Seven Miles Down: The Story of the Bathyscaphe Trieste (1961) by J. Piccard and R. S. Dietz. pp. 172-174. Published by the Putnam, New York.

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