Fish
Wolf Eel
Anarrhichthys ocellatus · also called wolf eel
The wolf eel is a two-metre, grey, spotted fish with a face only another wolf eel could love — and, as it turns out, usually does, because wolf eels pair off young and keep the same partner and the same rocky den for years. It is not an eel at all, but a long-bodied member of the wolffish family, built to reverse into a crevice and crush sea urchins with its molars.
Overview
Wolf eels live throughout the North Pacific, from Japan and the Aleutians down to southern California, on rocky reefs from the shallows to about 225 m deep. They reach roughly 2.4 m and 18 kg, with a very long, flattened grey body dappled with dark, pale-ringed spots and tapering to a point.
Not an eel
The eel-like shape is misleading. The wolf eel belongs to the wolffish family, a group of stocky, shell-crushing northern fish, and is essentially a wolffish stretched long so it can live wedged in reef cracks with just its head protruding.
Jaws for shellfish
The mouth combines canine-like grabbing teeth at the front with broad molars in the jaws and throat. That equipment lets the wolf eel eat sea urchins, crabs, mussels, clams, and snails, crunching straight through their shells. The same bite can badly injure a hand.
A den, and a partner
Adults form long-term pairs, frequently bonding while young and staying together for years. A pair shares one den, and when the female lays her large egg mass — up to about 10,000 eggs — both parents coil around it, guarding and fanning it for three to four months until it hatches.
A changing face
Juveniles are slender, bright orange with purple spots, and drift in open water. As they mature they settle to the reef and turn grey, and older animals, especially males, develop a heavily wrinkled, jowly face. Where they are not fished, wolf eels often grow tame enough to take food from a diver’s hand.
Wolf Eel: common questions
Is the wolf eel really an eel?
No. True eels belong to the order Anguilliformes and share features such as a particular larval stage and the loss of certain fins. The wolf eel has none of that. It is a member of the wolffish family, a group of stout, big-headed, shell-crushing fish of cold northern seas, and it is essentially a wolffish that has evolved a much longer, thinner body. That shape lets it back into deep, narrow cracks in a rocky reef and lie there with only its head showing. The name is simply a description of a long fish with a fierce-looking, toothy, wolf-like head.
Is a wolf eel dangerous to humans?
Not aggressively so. Wolf eels are generally calm and, where they are not hunted, often curious and even friendly toward divers, to the point of accepting handouts. The real hazard is the bite. Their jaws are built to crush sea urchins and crab shells, and a wolf eel that is cornered, speared, or offered a hand it mistakes for food can inflict a serious crushing wound. Divers who interact with them are advised to keep fingers clear of the mouth. Unprovoked attacks on people are not a feature of the species.
Do wolf eels mate for life?
They form durable pair bonds that can last many years. A male and female often pair while still young, well before they are ready to breed, and then occupy a den together on the reef. When the female lays her eggs, up to around 10,000 of them in a large gelatinous mass, both parents curl their long bodies around the clutch inside the den. They take turns guarding it and fanning it with their fins to keep it oxygenated for the roughly three to four months until the eggs hatch, rarely leaving it unattended.
Why do old wolf eels look so wrinkled?
As a wolf eel ages, the skin and connective tissue around the head thicken and fold, and the jaw muscles enlarge from a lifetime of crushing hard shells. Older animals, and males in particular, end up with a broad, lumpy, deeply creased face that looks almost like loose folds of grey rubber. This is a normal part of maturing rather than a sign of disease or injury, and a heavily jowled head is generally a mark of an old, well-established individual holding a good den on the reef.