Cartilaginous Fish at Axial

Skates and sharks have cartilage skeletons, and are classified separately from the Bony Fish.

Deep Sea Skate (Bathyraja abyssicola)

This Deep Sea Skate was photographed by the ROV ROPOS at 1756 m (5761 feet) beneath the ocean’s surface on the flank of Axial Seamount. Photo credit: NSF-OOI/UW/CSSF; Dive R1466; V11

Bathyraja abyssicola, the Deep Sea Skate, also known as the Abyssal Skate, is a relatively rare species of skate found at sites all around the North Pacific Ocean, yet is has been sighted several times at Axial Seamount.  This skate grows to be around 1.1 m in length at maturity, and can be found at depths between 0 and 3000 m. It is known to have a diet of mollusks, supplemented with bony fish. It is an egg-layer, with horned, oblong eggs 100 mm long and 65 mm wide.


Roughtail Skate (Bathyraja trachura)

A Roughtail Skate (Bathyraja trachura) was found resting near a vent on Axial Seamount. Photo credit: NSF-OOI/UW/CSSF; Dive R1617; V13

Bathyraja trachura, also known as the Roughtail Skate, is a species of skate found all across the North Pacific Ocean. The Roughtail Skate is a higher-order predator, eating mainly crustaceans and bony fish, although specimens have been found to eat a number of worms and other, smaller animals.
The Roughtail Skate is a bottom-dweller, and can be found all over Axial Seamount. This skate is typically 70 to 80 cm in length, although specimens can be found that are only 90 cm long. Juveniles are born at around 9 to 16 cm long, in distinctively oblong, horned eggs.
References: Interactions of Bathyraja trachura and Sympatric Fishes, Boyle

Blue Shark (Prionace glauca)

This blue shark was the highlight of the PD01A dive as he moved around the ROV. Credit: UW/NSF-OOI/WHOI; Dive J2-1367; V21

Blue sharks are a pelagic species that can be found worldwide in both tropical and cold temperate latitudes and are one of the most common pelagic species in the world. They are extremely migratory, traveling in search of denser areas of food and mates, and can make trips across the entire ocean throughout their lifetimes – a trip made easier by the large pectoral fins on either side of their body that they can use to ride ocean currents. They are named for the unique color of their skin and can grow up to 3 meters in length. Their diet generally consists of other smaller pelagic species, like fish and squid, and they regularly dive deeper to hunt. When they mate, the litters can contain more than 100 pups. Blue sharks are rarely a danger to humans, and incidents of shark attacks from a blue shark are incredibly infrequent.

They have been seen often during ROV descents, particularly at the near-surface float of the Axial Base deep profiler mooring. Presumably attracted to the lights and electrical signals of the ship and ROV, it is unknown whether or not there are many sharks in the area, or if we are encountering the same resident sharks on every visit.

Stevens, J. (2005, October 1). The IUCN Red List of Threatened Species. IUCN Red List of Threatened Species. Retrieved November 27, 2021, from