Anarhichas lupus: A “cool” fish

Image of A. lupus taken by Fiona Crouch, used with permission.

Anarhichas lupus, Linnaeus, 1758

Anarhichas lupus, is also known as the striped (Dutil, Proulx, Chouinard, Borcard & Larocque, 2014), common (Hellberg, Bjerkas, Vagnes, & Noga, 2013) or Atlantic wolffish. It was first described by Linnaeus in his 1758 book Systema Naturae, as a northern marine fish with a blunt head and cone-shaped teeth (Linné, C. v., 1758).

Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Perciformes
Suborder: Zoarcoidei
Family: Anarhichadidae
Genus: Anarhichas
Species: lupus

(Helfman, Collette, Facey, & Bowen, 2009)


Anarhichas lupus resides in the north Pacific Ocean, and is especially prevalent in the northern Atlantic Ocean, near the east and west coasts of Iceland (Helfman & Collette, 2009).

A. lupus generally maintains a territory spanning less than 100 miles from its birth and spawning site (Pampoulie & Skirnisdóttir, 2012). They remain in the benthic zone and in cold water, though the depth at which they reside may change slightly depending on temperature (Dutil & Proulx, 2014).

See Map (Global Biodiversity Information Facility, 2015)


They remain in rocky areas with rough sediment in (Dutil & Proulx, 2014) these subarctic waters (Gaudreau, Le François, Ditlecadet, Tveiten, Blier, 2009) and rarely travel more than 100 miles from where they spawn. (Pampoulie, Skirnisdóttir, Daníelsdóttir & Gunnarsson, 2012).

A. lupus shelter underneath and within rocks, in rough sediment where they find protection from predators and maintain the ability to surprise prey. They generally thrive at a range of depths between five and more than 250 meters below sea level, at a slope range between 15 and 30 degrees. In addition, they avoid the quickly flowing water of channels, choosing to remain closer to the shoreline. They are found in deepwater shelf and sloped habitats (Dutil & Proulx, 2014), where they stay until mating occurs and colder temperatures are required for proper egg development (Fairchild & Tallack, 2015).


This fish is long with a dorsal fin that starts above the pectoral fins and stretches across almost ¾ of the fish. It has anterior, bilateral pectoral fins, an anal fin that runs along the posterior half of the fish, and a laterally compressed, convex caudal fin.

  • Mass: approximately 45 kg (Helfman & Collette, 2009)
  • Length: approximately 2.5 m (Helfman & Collette, 2009)

In captivity, the males and females of this species appear very similar, however, in nature, the males weigh more and are usually greater in length than females (Fairchild & Tallack, 2015). Though there is some indication that these traits can vary according to temperature and development parameters, Atlantic wolffish 20 cm and longer average between 72 and 78 vertebrae and between 71 and 77 dorsal fin rays (Templeman, 1984). 


Atlantic wolffish may grow more rapidly in warmer water, based on comparisons between the east and west sides of Iceland. However, no significant genetic differences have been found between the two groups of the same species (Pampoulie & Skirnisdóttir, 2012) and different growth and maturation studies suggest conflicting results, and do not always take other factors, such as nutrition, into account (Gunnarsson, Hjörleifsson, Thórarinsson & Marteinsdóttir, 2008).


These fish are considered adults once they are older than two-years (Hellberg & Bjerkas, 2013), and when they reach 40 to 47 cm in length, and are older than five years, they begin courtship and mating. In fact, the larger the animal, the more fertile it is (Fairchild & Tallack, 2015).Mating rituals between one male and one female begin almost half a year before copulation takes place and include movement toward shallow waters (Fairchild, Tallack, Elzey & Armstrong, 2015).

Mating rituals between one male and one female begin almost half a year before copulation takes place and include movement toward shallow waters (Fairchild, Tallack, Elzey & Armstrong, 2015). Anarhichas lupus may crossbreed withAnarhichas minor, with which it shares a habitat off the coast of Canada (Gaudreau & Le François, 2009)

Males access females for fertilization purposes through the genital pore, and consequently need to produce less sperm than species not held to the process of internal fertilization. Wolffish ejaculate contains a range of immature spermatids, as well as fully-developed spermatozoa, which gain motility in the seminal fluid. These sperm are most likely to find and fertilize an egg up to ten hours post ejaculation (Pavlov, Knudsen, Emel’yanova & Moksness, 1997).

Though low light levels in captivity had little to no effect on sperm production, it can hinder female maturation and sexual development. (Pavlov & Knudsen, 1997).

The female passes all of the eggs, which measure between 4 and 7 mm, at one time (Gunnarsson & Hjörleifsson, 2008) with thick, viscous fluid into the water between 10 and 27 hours after fertilization. The accompanying fluid mitigates a decrease in yolk mass and prevents the eggs from absorbing excess water. This happens because the fluid’s osmolarity matches that of the internal egg – approximately 350-400 mOsm (Pavlov & Moksness, 1996).

The eggs adhere to one another as their shells harden, mitosis begins, and the embryos begin to develop. As this happens, the egg grouping also experiences a decrease in fluid from the female’s ovary, which accompanies osmolarity changes in the egg itself (Pavlov & Moksness, 1996).

Any attempt to remove a deceased embryo’s egg from the group can kill live, developing fish in the egg ball, yet its decay can also cause serious problems – leading to disease throughout the clutch. This issue complicates efforts to rear these fish for aquaculture (Pavlov & Moksness, 1996).

The main spawning season runs from September through April (Pampoulie & Skirnisdóttir, 2012). Increases in sperm production occur August through January, with a peak in December. This correlates with sperm production heights in captive fish, though breeding can potentially occur any time throughout the year (Pavlov & Knudsen, 1997). Researchers have observed breeding pairs as close as 5 meters to shore and noted that eggs maintained at temperatures less than 12 degrees C produced healthier offspring (Lamarre, François, Falk-Petersen & Blier, 2004).

The male guards the egg collection, or nest for almost a year, until the fry hatch and become self-sufficient (Pavlov & Knudsen, 1997).

Development within the egg takes up to 10 months (Fairchild & Tallack, 2015). This species measures approximately 20 mm when it hatches (Pampoulie & Skirnisdóttir, 2012). At that time, it has a complete digestive system and is functionally prepared to consume food (Lamarre & François, 2004).

The young of this species rarely leave the nesting area until they grow much larger (Pampoulie & Skirnisdóttir, 2012).


These sedentary predators hide in and around rocks, lunging out to attack and eat other fish, sea scallops, shrimp, crabs, mollusks, snails, slugs and echinoderms (Fairchild & Tallack, 2015) (Helfman & Collette, 2009).

Feeding behaviors change during the breeding season, at which time the animal slows or stops eating, while its body replaces the teeth necessary for collection and consumption of A. lupus’s hard-shelled prey (Fairchild & Tallack, 2015).


Other fish eat A. lupus, especially prior to their growth and maturation. This is evident from stomach content assessments of Gadus spp. (Gunnarsson & Hjörleifsson, 2008).


Captive cultivation of this species can be compromised by viral and bacterial infections, such as Aeromonas salmonicida, bacteria that causes visible dermal sores and loss of appetite. These types of infections can cause mortality and reduce yield (Hellberg, Moksness & Hoeie, 1996). In addition, this species is susceptible to infection by the protozoa Trichodina, which can cause issues in breeding facilities (Hellberg & Bjerkas, 2013).

This species produces antifreeze proteins to survive the cold temperatures of its habitat and allow for growth and reproduction in these conditions. The proteins are concentrated in the blood’s plasma, where they reduce its freezing point, keeping the fish alive in circumstances that would kill many other animals. (Desjardins, Le Francois, Fletcher & Blier, 2007). Fish-produced antifreeze proteins are valuable for human medication and have the potential for additional uses. It is best to obtain them during winter, when production of the protein is at its height in the animal.


This species can live more than three decades in the wild, (Fairchild & Tallack, 2015) but does not often get the opportunity to do so. As of May 2015, the Committee on the Status of Endangered Wildlife in Canada (COSEWIC), which meets yearly to assess the status of different species, lists Anarhichas lupus as one of 52 fish in the special concern category (COSEWIC, 2015). This process supports the Canadian Species at Risk Act (SARA) in identification and protection of endangered species’ habitats (Dutil & Proulx, 2014). In addition, the United States of America’s Endangered Species Act also shows this animal as a species of concern, and the country has not allowed fishing for this species since 2010 (Fairchild & Tallack, 2015).

Broodstock for research has been reared in Norway at the Institute of Marine Research, Flodevigen Marine Research Station. These fish are descendants of eggs harvested from the ocean between 1986 and 1988 (Pavlov & Knudsen, 1997).


  • COSEWIC. 2015. Canadian Wildlife Species at Risk. Committee on the Status of Endangered Wildlife in Canada. Website: [accessed 24 October 2015]
  • Desjardins, M., Le Francois, N., Fletcher, G., & Blier, P. (2007). High antifreeze protein levels in wolffish (Anarhichas lupus) make them an ideal candidate for culture in cold, potentially ice laden waters. Aquaculture.
  • Dutil, J.; Proulx, S.; Chouinard, P.; Borcard, D.; & Larocque, R. (2014).Distribution and environmental relationships of three species of wolffish (Anarhichas spp.) in the Gulf of St. Lawrence. Aquatic Conservation: Marine And Freshwater Ecosystems, (3).
  • Fairchild, E. A., Tallack, S., Elzey, S. P., & Armstrong, M. P. (2015).Spring feeding of Atlantic wolffish (Anarhichas lupus) on Stellwagen Bank, Massachusetts. Fishery Bulletin (Seattle), 113(2), 191-201.
  • Gaudreau, C. M.; Le François, N. R.; Ditlecadet, D.; Tveiten, H.; Blier, P. U. (2009). Characterization of the early-stages of the wolffish hybrid Anarhichas minor x Anarhichas lupus: conservation and aquaculture applications. Aquatic Living Resources, 22(3), 371-377. doi:10.1051/alr/2009030
  • Global Biodiversity Information Facility (2015) Data: Species Distribution by State. Online:
  • Gunnarsson, Á.; Hjörleifsson, E.; Thórarinsson, K.; & Marteinsdóttir, G. (2008). Growth, maturity and fecundity of female spotted wolffish Anarhichas minor in Icelandic waters. Journal Of Fish Biology, 73(6), 1393-1406. doi:10.1111/j.1095-8649.2008.02017.x
  • Hellberg, H.; Bjerkas, I.; Vagnes, O. B.; & Noga, E. J. (2013). Mast cells in common wolffish Anarhichas lupus L.: Ontogeny, distribution and association with lymphatic vessels. Fish & Shellfish Immunology, 351769-1778. doi:10.1016/j.fsi.2013.08.031.
  • Hellberg H.; Moksness E.; Hoeie S. (1996) Infection with atypical Aeromonas salmonicida in farmed common wolffish, Anarhichas lupus L.Journal Of Fish Diseases (United Kingdom) [serial online]. 1996;(4):329. Available from: AGRIS, Ipswich, MA. Accessed November 1, 2015.
  •  Helfman, G.; Collette, B.; Facey, D.; Bowen, B. (2009). The Diversity of Fishes: Biology, Evolution & Ecology, 2nd ed. John Wiley & Sons, Ltd. Pgs.
  • IBSS (2015). Catalog of Fishes. Institute for Biodiversity Science and Sustainability, California Academy of Sciences.
  • Lamarre, S. G.; François, N. L.; Falk-Petersen, I.; and Blier, P. U. (2004).SHORT COMMUNICATION Can digestive and metabolic enzyme activity levels predict growth rate and survival of newly hatched Atlantic wolffish ( Anarhichas lupus Olafsen)? Aquaculture Research, 35(6), 608-613. doi:10.1111/j.1365-2109.2004.01061.
  • Linné, C. v. (1758). Caroli Linnaei…systema naturae per regna tria naturae, secundum classes, ordines, genera, species, cum charateribus, differentiis, synonymis, locis.. Holmiae, impensis L. Salvii, 1758-59.
  • Pampoulie, C.; Skirnisdóttir, S.; Daníelsdóttir, A. K.; Gunnarsson, Á. (2012). Genetic structure of the Atlantic wolffish (Anarhichas lupus L.) at Icelandic fishing grounds: another evidence of panmixia in Iceland?ICES Journal Of Marine Science, (4).
  • Pavlov, D.; Moksness, E. (1996). Swelling of wolffish, Anarhichas lupus L., eggs and prevention of their adhesiveness. Aquaculture Research (United Kingdom), (6), 421.
  • Pavlov, D.; Knudsen, P.; Emel’yanova, N.; & Moksness, E. (1997).Spermatozoon ultrastructure and sperm production in wolffish (Anarhichas lupus), a species with internal fertilization sperm morphology. Aquatic Living Resources (France), ( 3), 187.
  • Templeman, W. (1984). Vertebral and Dorsal Fin-Ray Numbers in Atlantic Wolffish Anarhichas-Lupus of the Northwest Atlantic. Journal Of Northwest Atlantic Fishery Science, 5(2), 207-212.

A variation of this post has been submitted for publication to Animal Diversity Web.

Author: tatumlyles

Tatum Lyles Flick is a public relations practitioner, news and science writer, photographer, graphic designer and website designer with experience in industry, the news media, and academia.

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