How the barreleye uses its eyes
Barreleyes are small fish of the deep ocean: they usually grow to about six inches and inhabit waters roughly 2,000 to 2,600 feet below the surface. Their eyes point upward to detect prey, but can turn forward; the fish can see through the clear tissue covering its head. The Monterey Bay Aquarium describes the fish’s large, flat fins as helping it hold position or maneuver with precision.
That combination of vision and movement may help the fish feed among stinging siphonophore tentacles. MBARI’s account of earlier research says scientists hypothesize that the transparent shield protects the barreleye’s eyes as it picks off small crustaceans caught there. The shield is also important to studying the fish: fragile tissue can be damaged or lost when specimens are brought up in nets, as MBARI explains.
What the new recording adds
Footage of a living fish can show its head and eyes intact, rather than leaving researchers to infer their structure from damaged specimens. A report published by Phys.org, with material provided by MBARI, says the institute’s researchers will use the new footage in continued work on the species. The report identifies the recording as MBARI’s first of a barreleye in 4K; it does not establish that this was the first 4K recording by any organization.
The fish appeared on October 22, about 1,970 feet beneath the surface and roughly 55 miles offshore, during work from the research vessel David Packard. Using the ROV Doc Ricketts, the team filmed it for about 20 minutes. The MBARI-provided report calls this the institute’s 11th observation of the species in nearly 40 years and says its previous sighting was in 2021.
