The northern wolffish, or rock turbot, is a large marine fish of the family Anarhichadidae, native to the North Atlantic Ocean and Arctic Ocean. Other common names include the bull-headed catfish, blue catfish, broad-headed catfish, jelly wolffish, and the Arctic wolffish. Inuit in the Western Arctic do not distinguish between the northern wolffish and the Bering wolffish, calling both by the name akoak or akoaksaluk. This fish, sometimes considered "charmingly ugly", is found across the North Atlantic Ocean from north of Russia to the Scotian Shelf, off Nova Scotia. Its western Atlantic population declined dramatically during the 1980s, in part because it is often caught by fishers seeking other catch. The population was observed to decline by more than 90% from the late 1970s through the early 1990s. This species has been identified as Threatened by the Committee on the Status of Endangered Wildlife in Canada. It is listed under the federal Species at Risk Act and was afforded protection under the SARA as of June 2004. Under the SARA, a recovery strategy must be developed for this species. Additional protection is afforded through the federal Fisheries Act.
Characteristics
Northern wolffish are demersal fish. In summer, mature females lay up to 30,000 extremely large eggs in a nest on the sea floor. Adults are observed to make limited movements and are not migratory. The northern wolffish favours open continental-shelf water that is cold, usually between, and mainly at depths between. The fish is thought to prefer a rocky or muddy sea floor, but is found over all types of ocean bottoms. Sharp teeth and powerful jaws allow the northern wolffish to capture moving fish, starfish, sea urchins, and crabs. They also include some bottom-dwelling organisms in their diets. Their fearsome teeth, however, ensure they have few natural predators. They are not retained by fishermen for food because of their watery and jelly-like flesh. In the Canadian Arctic, northern wolffish occur primarily in Davis Strait, with their northernmost limit in Baffin Bay. A few records report them in the western Arctic, including as far west as Prince Patrick Island, NWT. In the North Atlantic, they are found on both sides of the ocean, from southern Newfoundland to the Barents Sea. In Canada, they occur primarily off the northeast Newfoundland/Labrador Shelf and the outer Grand Banks.
Identification
The northern wolffish is thick and heavyset, with a large head and teeth at the front of the jaw that are smaller and sharper than the other two wolffish species found in Atlantic Canada. The shape and size of its mouth and teeth allow it to capture moving prey. It can grow to in length and almost in weight. The northern wolffish has a more uniform body colour than the other wolffish species, ranging from grey to dark chocolate, sometimes with a light violet sheen.
Habitat and life history
Northern wolffish are found offshore in cold water, at depths ranging between the surface and, but most often below. These fish inhabit a wide range of bottom types, including silt, rocks, coarse sand, and shell hash. They use large rocks for shelter and nest building. Late in the year, females lay about 46,500 large eggs which sink to the sea floor, where they are guarded in nests by the males until they hatch. Growth rates are slow, and they mature at five years or older. Their lifespans are at least 12 years. Unlike other wolffishes, northerns have been found off the bottom during both the juvenile and adult stages. The species does not form large schools or undertake long migrations. This fish feeds in open water on comb jellies and jellyfish, and on bottom-living crustaceans and invertebrates, such as crabs, sea urchins, brittle stars, and starfish.
Threats
No direct studies of factors responsible for the observed declines in abundance have been conducted, but overfishing and habitat alteration are believed to have played a role. This species is not targeted by the fishing industry, but bycatch mortality by offshore trawlers and long-liners is considered a threat. In addition, activities that disturb the ocean bottom, such as trawling, may damage spawning habitat.
Similar species
The northern wolffish can be distinguished from the spotted wolffish and the Atlantic wolffish by its more uniform body colour and its soft, jelly-like musculature. Its head is also proportionally larger to its body and its upper lip is thick and covered with papillae.
Conservation status
The northern wolffish is protected under the Canadian federal Species at Risk Act. A recovery team for the northern and spotted wolffish has almost completed a recovery strategy and plan for both species. The strategy provides a framework for improving the status of wolffish through an enhanced understanding of their life history, potential sources of harm, and implementing management measures such as live release of captured wolffish. The plan also includes habitat stewardship and educational activities designed to involve stakeholders and inform the public.
