Local Streams

Ratfish: The most abundant resident fish in Puget Sound

The waters of the Pacific Northwest are home to a tremendous number of fascinating fish…one of the most unusual looking, but common, deeper water fishes is the spotted ratfish. It is estimated that there are 200 million ratfish in Puget Sound, which makes up approximately 70% of Puget Sound's fish mass!

Fun Creature Fact:
Ratfish make up 70% of Puget Sound's total fish mass!

Spotted ratfish, Hydrolagus colliei, are cartilaginous fish (meaning their skeletons are composed of cartilage, like sharks) and are related to sharks, rays and skates. They can be found from south Alaska to Baja California. They are primarily brown in color, with hues of gold, blue and green and covered in small white dots that act as camouflage.

The ratfish body is long, up to 38 inches, tapering to a long tail that makes up almost half its body length and does not have scales. The fins of a ratfish are triangular in shape and the dorsal fin (on top of the body) has a sharp venomous spine. Like most deep sea fishes, ratfish cannot regulate the amount of light coming into their eyes, so they have a special adaptation called "tapetum lucidum" that reflects light back to the retina, causing it to glow bright green, similar to cat's eyes.

Ratfish are a deep, cold water dwelling fish that have been found in depths ranging from 40-3,000 feet! They prefer mud and rocky bottom habitats, and, as their distribution range moves more southward they move into deeper water with water temperatures of 45-48 °F (7-9 °C).

Ratfish are poor swimmers and slowly swim along the saltwater floor tracking their prey. They locate prey primarily though electroreception (the ability to detect electrical currents from muscle movements) and smell. Ratfish have a plate of tiny specialized teeth designed to cut through the hard shells of shellfish and crustaceans. They eat clams, crabs, shrimps, polychaete worms and small benthic fishes, including other ratfish.

Like sharks, ratfish produce only two eggs during spawning and spawn in the spring and fall. The female ratfish releases egg cases and each egg case attaches to the seabed or sediments where it takes approximately one year to incubate, leaving them vulnerable to predation. Hatchlings are smaller (5.5 inches) versions of the adult and are selfsufficient upon hatching.

Currently, there are no conservation measures taken for spotted ratfish as they are so abundant. However, with the restrictions on trawling gear to avoid fish bycatch (incidental, non-targeted catch), ratfish also benefit as less are caught incidentally.

Where can you see ratfish? Visit the Seattle Aquarium or the Oregon Coast Aquarium in Newport, Oregon.