One of the unusual black corals documented making circles in the sediment during Dive 14 at Explorer Ridge Deep.

One of the unusual black corals documented making circles in the sediment during Dive 14 at Explorer Ridge Deep. Image courtesy of the NOAA Office of Ocean Exploration and Research, 2016 Deepwater Exploration of the Marianas. Download larger version (jpg, 981 KB).

Dive 14: Explorer Ridge Deep
20°46.008'N, 145°5.022'E, 2,598 meters
July 1, 2016
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First Sighting

“This is just remarkable.” That’s how Bruce Mundy, fishery biologist with the NOAA National Marine Fisheries Service, Pacific Islands Fisheries Science Center, described seeing live video of this eel-like fish. What makes it so remarkable is the fact that a fish in this family has never been seen live – until now.

Video of the fish was captured during an expedition on NOAA Ship Okeanos Explorer to explore the unknown and poorly known deep waters of the Marianas Trench Marine National Monument and the Commonwealth of the Northern Mariana Islands. Seen while exploring a ridge feature at a depth of ~2,500 meters, the fish measured about 10 centimeters long. It is in the same order (Ophidiiformes) as cusk eels, but belongs to a distinct family (Aphyonidae). According to the experts, this is the first time that a fish in the family Aphyonidae has ever been seen alive!

With its transparent, gelatinous skin, which lacked scales, and its highly reduced eyes that lacked pigment, the fish was truly a remarkable – and ghostly – find. In fact, some viewers noted it was basically the “fish version of Casper the octopus,” in reference to an octopus seen during a February expedition on the Okeanos Explorer off of Hawaii that was likely a new species.

One thing is certain – this was indeed an exciting find that highlights, once again, how much we still have to learn about our vast, and unexplored, ocean.

Anyone with an Internet connection is invited to follow the expedition LIVE, with dives happening between now and July 8.

This expedition is part of the three-year Campaign to Address the Pacific monument Science, Technology, and Ocean NEeds (CAPSTONE), an effort to explore high-priority unknown areas in the Pacific marine national monuments. The central and western Pacific marine national monuments and national marine sanctuaries encompass over 742,000 square miles of emergent land, coral reef, ocean, and maritime heritage resources as well as harbor numerous protected species and likely an abundance of undiscovered resources. CAPSTONE provides timely, actionable information to support science-based decision making regarding some of these last relatively pristine marine ecosystems on the planet.

Heard on the video

Bruce Mundy
Fishery Biologist
NOAA National Marine Fisheries Service, Pacific Islands Fisheries Science Center

Dr. Shirley Pomponi (bio)
Biology Science Team Lead, Deepwater Exploration of the Marianas Leg 3
Research Professor and Executive Director of the NOAA Cooperative Institute for Ocean Exploration, Research, and Technology, Harbor Branch Oceanographic Institute, Florida Atlantic University; Professor of Marine Biotechnology at Wageningen University, Netherlands.

Video courtesy of the NOAA Office of Ocean Exploration and Research, 2016 Deepwater Exploration of the Marianas. Download (mp4, 110.8 MB)

Dive 14 began over a smooth seafloor surface at 2,598 meters, with a pale-brown sediment and numerous tiny foraminiferal tests. Most of the beginning of the dive was on what appeared to be a talus slope, approximately 45° slope, covered by sediment. As remotely operated vehicle Deep Discoverer (D2) ascended the talus slope, it became steeper, eventually reaching as high as 55°. Higher up the slope, D2 documented several outcrops, sediment cutes, columnar jointing, and boulders. The dive wrapped up on a smooth, nearly vertical wall with a massive smooth surface. Without a doubt, the most exciting biological discovery today was the aphyonid fish, about 10 centimeters long, with transparent skin and highly reduced eyes. According to the experts, this is the first time that a fish in the family Aphyonidae has ever been seen alive! Other unusual findings during the dive included black corals (Schizopathes sp.) that were observed on their side as they made circles in the sediment; carnivorous and hexactinellid sponges; and a pattern of holes – known as Paleodictyon nodosum, whose origin is unknown.