Creature Feature: The Spotted Ratfish | NEC - Northcoast Environmental Center

Liam Gwynn, EcoNews Intern

In the dark void of the ocean's depths, an ancient relative of the shark prowls the murky water in search of bottom-dwellers to feed on. Its skin is pale, almost translucent, and it hunts its prey by utilizing two of its most valuable tools: firstly, its ability to follow other species' electrical stimuli, and secondly, its incredible sense of smell. These ghostly apparitions are known as the Spotted Ratfish (Hydrolagus colliei).

The Spotted Ratfish has several unique characteristics that make it one of the more bizarre and interesting species found off the Humboldt coast. Their pectoral fins are longer than most fish and shark species. This allows them to swim mostly with their pectoral fins instead of their dorsal fins like other species, giving them a graceful flying appearance. They are completely scaleless, unlike most sharks, and their skin is smooth and often multicolored. They have a long poisonous barb on their dorsal fin that gives them protection from larger predators. This barb isn't lethal to humans but it is known among fishermen to have an excruciatingly painful sting. The poisonous barb is even more effective as a defense mechanism against larger marine predators. Between 2006 and 2011, seven harbor seals were killed off the coast of Washington after misguided attempts to snack on Spotted Ratfish that swam closer to shore than they typically swim. The spine is thick and sharp enough to cut through the seal blubber and into their vital organs.

The Spotted Ratfish is a member of the Chimaera genus. Less known than their shark cousins, Chimaera shared common ancestors with sharks around 400 million years ago. What differentiates them from their better-known cousins are their longer pectoral fins, unique teeth, and their upper jaws which are fused to their skulls. They can be found from Alaska to Baja California but are most commonly found between Northern California and British Columbia and have been recorded in Humboldt Bay and the surrounding coastal depths. The Spotted Ratfish are small in size with males growing up to around 24 inches and females growing to around 38 inches. They are almost entirely found on the ocean floor which has made studying them more complicated and is one of the reasons they are so rarely discussed.

One of the strangest aspects of the Spotted Ratfish is how their teeth differ from almost any other species. While sharks have long rows of constantly replaced teeth, Spotted Ratfish have three permanent plate-like teeth that let them grind and break apart the shells of their prey. These plated teeth are highly effective and allow them to feed on a variety of species including clams, crabs, starfish, sea urchins, and worms among other bottom-dwelling species. Ratfish are opportunistic feeders so they will eat just about anything they can get through their jaws.

Despite their poisonous barb and swift swimming capability, Spotted Ratfish have several predators to watch out for. Medium and large sharks will occasionally feed on Ratfish; however, their main competitor and predator is the Pacific Halibut. Given that both species are bottom feeders, the Spotted Ratfish and the Pacific Halibut are in direct competition. With halibut growing up to nine feet long, the Spotted Ratfish make easy prey for the massive fish.

One predator the Ratfish rarely has to worry about is us. Today, Spotted Ratfish are almost never intentionally fished. While edible, their meat reportedly tastes bland and rubbery and since they generally swim at depths ranging from 600  to 3000 feet, they are hardly ever caught by sports fishermen. The greatest threat they face from humans is being caught accidentally in fisheries, longlines, or otter trawls. Despite the occasional bycatch, aversion to the meat of Spotted Ratfish has allowed their populations to stay strong while many of their cousins teeter on the verge of extinction. The Spotted Ratfish remains a prime example of the incredible and sometimes surreal biodiversity that can be found around Humboldt Bay and yet another reason why it is so important to protect these habitats at all costs.