Northern wolffish

Northern wolffish
Conservation status
Threatened in Canada
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
Order:	Perciformes
Family:	Anarhichadidae
Genus:	Anarhichas
Species:	Anarhichas denticulatus

The northern wolffish (Anarhichas denticulatus), or rock turbot, is a large marine fish of the Anarhichadidae family. Other common names include the Bull-headed Catfish, Blue Catfish, Broad-headed Catfish, Jelly Wolffish, and the Arctic Wolffish. Inuit in the Western Arctic (Bathurst Inlet) do not distinguish between the Northern Wolffish and the Bering Wolffish (A. orientalis), calling both by the name akoak or akoaksaluk ("old woman fish").

This fish, sometimes considered "charmingly ugly"¹ 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 the northern wolffish, while not sought after itself, is often caught by fishers seeking other catch. The population was observed to decline by more than 90 percent 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 (COSEWIC). It is listed under the federal Species at Risk Act (SARA) and was afforded protection under the SARA as of June 2004. Additional protection is afforded through the federal Fisheries Act. Under the SARA, a recovery strategy must be developed for this species.²

About the northern wolffish

Northern wolffish are pelagic fish—spending a great deal of its time swimming and feeding on moving creatures in open waters. In summer, mature females lay up to 30,000 extremely large eggs in a nest on the sea floor. Adult northern wolffish are observed to make limited movements and are non-migratory. The northern wolffish favours open continental-shelf water that is cold—usually between 2°C to 5°C—and mainly at depths between 400 and 1000 metres. The fish is thought to prefer a rocky or muddy sea floor but is found over all types of ocean bottoms.

Razor-sharp teeth and powerful jaws allow the northern wolffish to capture moving (pelagic) fish, starfish, sea urchins, and crabs. They also include some bottom-dwelling (benthic) organisms in their diet. Its fearsome teeth, however, ensure that it has few natural predators. It is not retained by fishers for food because of its watery and jelly-like flesh.

Distribution: In the Arctic, Northern Wolffish occur primarily in Davis Strait with their northernmost limit in Baffin Bay. There are a few records in the western Arctic including as far west as Prince Patrick Island, NWT. In the North Atlantic, Northern Wolffish are found on both sides of the ocean, from southern Newfoundland to the Barents Sea. In Canada, it occurs primarily off northeast Newfoundland/Labrador Shelf and the outer Grand Banks.

How to recognize the northern wolffish

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 (pelagic) prey. It can grow to 145 centimetres in length and almost 20 kilograms 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 (below 5°C) at depths ranging between the surface and 1200 m, but most often below 150 m. This fish inhabits a wide range of bottom types including silt, rocky, coarse sand, and shell hash. They use large rocks for shelter and nest building. Late in the year, females lay approximately 46,500 large eggs (up to 8 mm in diameter) which sink to the sea floor where they are guarded in nests by the males until they hatch. Growth rates are slow and fish become mature at five years or older. Its lifespan is at least 12 years. Unlike other Wolffishes, the Northern has been found off the bottom during both the juvenile and adult stages. The species does not form large schools or undertake long migrations. Diet: 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

There are no direct studies of factors responsible for the observed declines in abundance but it is believed that overfishing and habitat alteration have played a role. This fish species is not targeted by the fishing industry, however, by-catch 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 (A. minor) and the Atlantic wolffish (A. lupus) 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.

What’s being done

The northern wolffish is protected under the Canadian federal Species at Risk Act (SARA). A recovery team for the northern and spotted wolffish has almost completed a recovery strategy and plan for both species.¹ 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.

References

1. Department of Fisheries and Oceans Canada, [1] 2. Species at Risk Act Public Registry, Environment Canada, Accessed at: [2] 3. Ibid.

Northern Wolffish, Aquatic Species at Risk, Department of Fisheries and Oceans, Canada. [3] The Northern Wolffish…a Species at Risk in the North, Department of Fisheries and Oceans, Canada, 2005 Other Text Sources: Scott and Scott 1988; Quinn 2002 (COSEWIC Status Report); Stock Status Report 2004/031 2003. For more information, visit the SARA Registry Website at [www.SARAregistry.gc.ca] and the Fisheries and Oceans Canada (DFO) Website.

External links