These relatives of sharks and rays favor particular “neighborhoods” on the deep seafloor.

Skates are fishes related to sharks and rays. They have a flattened body with a pointy, spade-like snout. They swim and glide using a pair of large, wing-like pectoral fins. Skates are found in a variety of ocean habitats around the world. While we know a lot about the skates that dwell in shallow coastal waters, we know relatively little about those that call the ocean’s inky depths their home.

Observations from our advanced underwater robots have provided valuable information about deep-dwelling skates. Video recorded by our robotic submersibles is cataloged with detailed environmental data. Studying our archive of thousands of skate sightings revealed new information about the depth ranges, preferred habitats, and unique behaviors of deep-sea skates (Bathyraja sp.).

At least six species of Bathyraja live off the California coast. Each is adapted to a particular habitat and specializes in a distinct diet.

We often encounter skates resting on the sediment or skimming across the seafloor. Along with their broad pectoral fins, some skates use their pelvic fins like legs to maneuver while hunting along the bottom or to propel themselves off the seafloor when danger approaches. The abyssal skate (Bathyraja abyssicola) even uses those pelvic fins to “walk” up the rocky walls of submarine canyons.

A striking ghostly white coloration makes the spiny skate (Bathyraja spinosissima) easy to spot. These active swimmers hover and glide well above the seafloor, while their relatives tend to stay close to the bottom. This species is especially common in rocky lava fields and is known to reproduce near hydrothermal vents. The vents bathe the skate’s leathery egg cases in warm water, speeding up the development of embryos inside.

The roughtail skate (Bathyraja trachura) is especially tolerant of low-oxygen environments. While other skates may occasionally visit these oxygen-starved waters, this is the only species that can stay there consistently. Climate change threatens to expand the ocean’s oxygen minimum zones. Learning which species can tolerate these hypoxic conditions helps us understand what biological communities may look like in the future.

Of all of our local Bathyraja, the fine-spined skate (Bathyraja microtrachys) favors the deepest depths. However, some of our observations in the outer Monterey Canyon may actually represent a previously unknown species. These skates had a unique coloration and a shorter tail, indicating that we may have encountered a species new to science.

Our research is filling in the gaps in scientists’ baseline knowledge of rarely-seen deep-sea skates. These data become especially important as climate change and overfishing continue to threaten biological communities. The more we learn about deep-sea sharks, skates, and rays, the better we can protect them and their habitats.