Fish
Atlantic Wolffish
Anarhichas lupus · also called Atlantic wolffish, seawolf, devil fish, ocean catfish
The Atlantic wolffish has one of the most alarming faces in the North Atlantic — a heavy, blunt head, a permanent scowl, and a mouth bristling with fangs and paved with molars. It uses all of that hardware to eat sea urchins and clams, it lives in water cold enough to freeze an ordinary fish solid, and it is a surprisingly devoted father.
Overview
Atlantic wolffish live on both sides of the cold North Atlantic, on rocky and boulder-strewn bottoms from about 20 to 500 metres down. They are solitary and territorial, each fish occupying a crevice or den among the rocks and venturing out to feed. The body is long, tapering, and scaleless, more eel-like than the shape of a typical fish, and colour ranges from purplish-brown to slate-grey with darker bars.
A face built for shellfish
The wolffish’s teeth are a specialised crushing kit: strong canine fangs at the front for prying prey off rocks and gripping, then broad molars and bony plates across the palate and lower jaw for pulverising shells. The whole set is shed and regrown every year. The diet is almost entirely hard-shelled invertebrates — sea urchins, crabs, whelks, cockles, clams — crushed whole.
Antifreeze
In water that hovers near -1 °C for months, a normal fish’s blood would begin to freeze. The wolffish makes antifreeze proteins that latch onto forming ice crystals and stop them growing, keeping its body fluids liquid. The same class of proteins, from various cold-water fish, is now used to control ice texture in commercial ice cream.
A guarding father
Unusually for a northern fish, the wolffish practises parental care: the female lays a large ball of eggs on the seabed, and the male guards it for around four months until the young hatch as well-developed juveniles.
Why it matters
By eating large numbers of sea urchins and invasive green crabs, the wolffish helps keep kelp forests and shellfish beds intact. Where wolffish disappear, urchin populations can explode and graze kelp down to bare “urchin barrens.”
Status
The Atlantic wolffish is globally Least Concern but locally depleted, chiefly as trawl bycatch, compounded by slow growth, late maturity, den fidelity, and damage to its rocky habitat from bottom trawling. It is a US species of concern, and targeted fishing for it is prohibited in parts of its range.
Atlantic Wolffish: common questions
Is the Atlantic wolffish dangerous to people?
Not in the water. It is a solitary, sedentary fish that spends most of its time wedged in a rocky den, and it has no interest in humans. Its bite, however, is genuinely powerful — it is built to crack sea urchins and thick clam shells — so a hooked or netted wolffish handled carelessly on a boat can inflict a serious crushing bite, and fishers treat them with respect. Names like "seawolf" and "devil fish" come from the toothy face and that bite, not from any aggression toward swimmers.
Why does a fish need antifreeze?
The Atlantic wolffish lives in water that can sit at or just below 0°C for months. Seawater freezes at about -1.9°C, but fish blood is less salty and would normally freeze around -0.8°C, so in the coldest water ice crystals could start to form inside the fish and kill it. The wolffish produces special antifreeze (or "ice-structuring") proteins that bind to tiny ice crystals as they begin to form and stop them growing, effectively lowering the freezing point of its body fluids. Several other polar and subpolar fish have independently evolved similar proteins, which are now used commercially in ice cream and frozen foods to control ice texture.
What does the wolffish eat with all those teeth?
Almost entirely hard-shelled, slow-moving invertebrates. It uses the front fangs to grip and lever prey off rocks or out of the sediment, then moves it back to the broad molars and palate plates and crushes it, shell and all. Sea urchins are a favourite, along with green crabs, hermit crabs, whelks, cockles, and clams. Because it removes large numbers of sea urchins and invasive green crabs, the wolffish is considered important for the health of kelp forests and native shellfish beds.
Why has the Atlantic wolffish declined?
It is mainly caught as bycatch in trawls targeting other bottom fish, and because it grows slowly, matures late, lays a single clutch a year, and is strongly attached to specific rocky den sites, it recovers slowly and local populations are easily fished down. Bottom trawling also damages the rocky, structured habitat it depends on. It is not globally threatened, but numbers in the northwest Atlantic have dropped enough that it is a US "species of concern," and directed fishing for it is banned in some areas.