Spotted Ratfish   Hydrolagus colliei

Ratfish (also called chimaeras) are a cartilaginous fish that have an odd, rabbit-like mouth filled with grinding teeth (hence their name). Ratfish are an ancient species that are closely related to sharks.   They evolved during the Devonian period (about 340 million years ago), and really haven’t changed since that time. 

Female ratfish grow to about 3’, with the males being significantly smaller.  Males are easy to identify by the claspers located behind the pelvic fin and the doorknocker-like cephalic tentaculum on its forehead (a clasping organ used to grasp the female during mating). 

Ratfish feed by crushing shrimp, clams, worms, sea stars and fish with their incisors.  They are found primarily on sand or muddy bottoms from SE Alaska to Baja California at depths from 0 to 3000’.  They actually prefer deeper water, and the greatest concentrations can be found from 600’ to 1500’ of depth off our coast. 

 Divers frequently encounter ratfish in shallow water during late spring as they head to the shallows to mate.  During a recent dive we observed 4 ratfish that were circling individual shallow depressions in the sand, looking for a mate.  Each boldly swam right up to our lights and hovered inches away before returning to their little patch of ground. Once they complete their courtship rituals, the female will lay a spoon shaped egg capsule. The extrusion process can last up to 30 hours after which the capsule is towed along behind the female for about five days until it is planted in the sand. 

Ratfish look somewhat odd as they swim because they flap their large, wing-like pectoral fins for locomotion rather than using their tail.  The spine of the ratfish is venomous, but only dangerous if you’re dumb enough to actually grab the fish.  The spine is only used defensively, and the species is very mild mannered and approachable by divers.  It’s easy to tell when you are beginning to frighten the fish, as it will briefly raise it’s spine in a defensive pose (i.e. it’s time to give the fish a little more space). 

Ratfish are one of my favorite fish species.  They are so ugly they are cute, and I can’t help but thinking that someone made a mistake when they were putting the fish together some 340 million years ago.

 Additional  Spotted Ratfish photos can be found in the Ratfish Photo Galleries.