Cusk have a range and distribution similar to that of Atlantic cod. They are found in the northwest Atlantic Ocean from New Jersey to the Strait of Belle Isle in Canada, along the coast of Newfoundland, and occasionally off the southern tip of Greenland. In the northeast Atlantic Ocean, they are found along the coasts of Iceland, Scandinavia, and northern Ireland and England, including the northern North Sea. (Cohen, et al., 1990; Tyus, 2012; Wootton, 1990)
Cusk are benthic fish, inhabiting rough-bottom areas in the cooler waters of the North Atlantic. Cusk are most often located over rocky, mud, or gravel bottoms and can be found over seamounts and knolls; they are rarely ever found over flat, sandy bottoms. A deep-water fish, cusk seldomly occur in water more shallow than 20-30 meters and are most commonly found at depths of 150-450 meters in the northeast Atlantic and from 18-149 meters in the northwest Atlantic. They can be found in waters as deep as 1,000 meters and in water temperatures from 0-10°C. (Bailly, 2013; Cohen, et al., 1990; Luna and Capuli, 2012; Nelson, 1994)
Cusk are variable in color, with their primary dorsal coloration ranging from dark grey to a rusty or greenish brown, fading through the sides to a pale white or gray ventrally. Their vertical fins have dark margins edged in white. Adults are typically more dully-colored than juveniles, who may have six transverse yellow bands. Cusk have one long dorsal fin, one anal fin, short pectoral fins, and rounded caudal fins, as well as a chin barbel. They are easily distinguished from other members of the family Gadidae by their single dorsal fin and characteristically rounded caudal fin. Most cusk grow to be less than 100 cm in length (average 50-95 cm), with an average weight of 12 kg (maximum recorded weight 30 kg). There are no polymorphic forms or documented seasonal variations, and populations on both sides of the Atlantic are remarkably similar in size and weight, differing only slightly in color. (Cohen, et al., 1990; Luna and Capuli, 2012; Nelson, 1994; Shackell, et al., 2005)
Females release up to 2 million buoyant eggs at a time during spawning season. Eggs hatch into planktonic young, which remain in coastal, shallow-water environments until they grow to a length of about 5 centimeters, becoming benthic thereafter. These fish have a relatively slow growth rate, reaching 22 centimeters on average by age 6 and gaining about 10 centimeters per year thereafter. Sexual maturity is achieved at about 50 centimeters in length (8-10 years of age). (Cohen, et al., 1990; Shackell, et al., 2005; Tyus, 2012)
Little is known about cusk mating systems, but they are assumed to be similar to that of its relative, Atlantic cod (Gadus morhua). While Atlantic cod are generally more active than cusk, they do not have rigorous courtship behaviors. A male will court a female with fin displays and "grunting," after which the female will allow the male to invert himself beneath her, where fertilization of the egg clutch occurs. Cusk are solitary outside of breeding season and are assumed to be polygynous. Spawning occurs once a year between April and July and there are spawning grounds throughout this species' range, with some notable areas between Scotland and Iceland, along the edges of the Shetland and Faeroe Islands, in the northern North Sea, and in the Gulf of Maine. (Cohen, et al., 1990; Nelson, 1994; Tyus, 2012)
Cusk can live for up to 20 years in the wild. As benthic fish that use primitive gas bladders for buoyancy, removal to the surface, with its related rapid change in pressure, is often immediately fatal. Commercial fishing is generally considered to be the greatest limiting factor in cusk longevity, as they are often by-catch of Atlantic halibut, cod, pollock, and haddock. ("Cusk (Brosme brosme)", 2009; Cohen, et al., 1990; Matthews, 1927; Nelson, 1994)
Cusk are solitary bottom foragers and are sluggish, generally poor swimmers. Their activity levels are not regulated by diurnal patterns. They expend little or no energy in long distance travel, instead slowly covering expanses of territory and foraging as they pass through. They have no discernible social structure, and are social only during mating. (Bailly, 2013; Cohen, et al., 1990; Tyus, 2012; Wootton, 1990)
Anecdotal evidence from fishing communities suggests that cusk do not have large home ranges. If cusk are found on new fishing grounds, they can be fished out of existence in that locality in a short period of time, with no replenishment. It is assumed that they migrate only in terms of depth, not range. (Cohen, et al., 1990; Matthews, 1927)
Cusk rarely communicate with each other, and when they do it is most likely in order to locate a mate. Little is known of how this communication occurs, but it likely involves chemical signaling by females. Cusk live in deep water with little to no ambient light; their eyes are large and upturned for predator and prey detection. They have a sensory barbel on their chins that can detect vibrations, guide them over terrain, and may serve in a chemosensory capacity. They have moderately well-developed hearing and pressure sensitivity (through the lateral line system), and hunt primarily by sight, smell, or barbel detection. (Tyus, 2012; Wootton, 1990)
Cusks are carnivorous foragers of small fishes, crabs and other crustaceans, mollusks, starfishes, and other small, soft-bodied, benthic invertebrates. Some examples of prey items include gurnard (Family Triglidae), pea crabs (Pinnotheres pisum), caridean shrimp (Crangon crangon), and margarita snails (Margarites pupillus). They are likely opportunistic scavengers as well, scavenging freshly dead organisms, if found. (Bailly, 2013; Cohen, et al., 1990; Matthews, 1927; Shackell, et al., 2005; Tyus, 2012)
The primary predators of adult cusk are humans; these fish share nearly identical habitats with Atlantic cod, a staple of the world's fishing industry. In 1987, an estimated 46,254 metric tons of cusk were caught as accidental bycatch and subsequently consumed; landings, as well as size of fish caught, have steadily decreased over the years (about 74 metric tons in U.S. waters in 2004), likely a sign of overall population decreases. Besides humans, cusk are preyed upon by sand sharks, dogfish, thorny skates, harbor seals, tuna, and porpoises. They rely on their slow movement and cryptic coloration to avoid detection by the roving predators they encounter. Additionally, the rocky substrate they inhabit allows them to seek cover in inaccessible crags if they feel threatened. ("Cusk (Brosme brosme)", 2009; Bailly, 2013; Cohen, et al., 1990; Matthews, 1927; Nelson, 1994)
Cusk are predators, consuming creatures that are either omnivores, detriovores, herbivores, filter feeders, or other small opportunistic carnivores. While they are not the preferred prey for any particular species, they are nonetheless occasional prey for many benthic predators and pelagic diving predators. They may be hosts to a variety of parasites, including roundworms, flatworms, and copepods. ("A biological survey of the waters of Woods Hole and vicinity: Part II, Section IV: A catalogue of the marine flora", 1911; Gibson, 1996; Luna and Capuli, 2012; McDonald and Margolis, 1995; Nelson, 1994; Tyus, 2012; Wootton, 1990)
Cusk are a food item for humans. Because cusk and Atlantic cod are so similar in taste and appearance, they are often handled the same once caught and have the same pound for pound selling weight. This makes cusk both a valuable economic resource for fisheries and an important source of food for many individuals. (Cohen, et al., 1990; Matthews, 1927; Nelson, 1994)
Cusk are considered to be a threatened species by the Committee on the Status of Endangered Wildlife Species in Canada and a species of concern by the U.S. National Marine Fisheries service. Cusk have not yet been assessed by the IUCN. It is not considered a threatened species by CITES. Due to its decreasing population and usefulness as a food source it is garnering additional attention. ("Brosme Brosme", 2012; "Cusk (Brosme brosme)", 2009; "Recovery potential assessment for Cusk (Brosme brosme)", 2008; Tyus, 2012; Wootton, 1990)
Eric Dultz (author), The College of New Jersey, Matthew Wund (editor), The College of New Jersey, Jeremy Wright (editor), University of Michigan-Ann Arbor.
the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.
uses sound to communicate
Referring to an animal that lives on or near the bottom of a body of water. Also an aquatic biome consisting of the ocean bottom below the pelagic and coastal zones. Bottom habitats in the very deepest oceans (below 9000 m) are sometimes referred to as the abyssal zone. see also oceanic vent.
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
an animal that mainly eats meat
flesh of dead animals.
uses smells or other chemicals to communicate
active at dawn and dusk
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
fertilization takes place outside the female's body
union of egg and spermatozoan
A substance that provides both nutrients and energy to a living thing.
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
eats mollusks, members of Phylum Mollusca
having the capacity to move from one place to another.
specialized for swimming
the area in which the animal is naturally found, the region in which it is endemic.
active during the night
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
chemicals released into air or water that are detected by and responded to by other animals of the same species
an animal that mainly eats fish
having more than one female as a mate at one time
mainly lives in oceans, seas, or other bodies of salt water.
an animal that mainly eats dead animals
breeding is confined to a particular season
remains in the same area
reproduction that includes combining the genetic contribution of two individuals, a male and a female
uses touch to communicate
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
movements of a hard surface that are produced by animals as signals to others
uses sight to communicate
Department of Commerce and Labor. A biological survey of the waters of Woods Hole and vicinity: Part II, Section IV: A catalogue of the marine flora. 31/2. Washington, D.C.: Government Printing Office. 1911. Accessed February 20, 2013 at http://books.google.com/books?id=M6BUAAAAYAAJ&pg=PA771&lpg=PA771&dq=parasite+brosme+brosme&source=bl&ots=WCcX5B-U8A&sig=hTDd_KcyaT7AI8SEcPp7r7cpwjs&hl=en&sa=X&ei=zPskUcLpO4Xy0gGq9ICoCQ&ved=0CCkQ6AEwBQ#v=onepage&q&f=false.
2012. "Brosme Brosme" (On-line). The IUCN Red List of Threatened Species. Accessed February 20, 2013 at http://www.iucnredlist.org/search.
2009. "Cusk (Brosme brosme)" (On-line). NOAA Fisheries: Office of Protected Resources. Accessed February 20, 2013 at http://www.nmfs.noaa.gov/pr/species/fish/cusk.htm.
Canadian Science Advisory Secretariat. Recovery potential assessment for Cusk (Brosme brosme). 2008/024. Ottawa, CA: Fisheries and Oceans Canada. 2008. Accessed February 20, 2013 at http://www.dfo-mpo.gc.ca/csas/Csas/Publications/SAR-AS/2008/SAR-AS2008_024_E.pdf.
Bailly, N. 2013. "Brosme brosme (Ascanius, 1772)" (On-line). World Register of Marine Species. Accessed February 20, 2013 at http://www.marinespecies.org/aphia.php?p=taxdetails&id=126447.
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Gibson, D. 1996. Trematoda. Pp. 373 pp. in L Margolis, Z Kabata, eds. Guide to the parasites of fishes of Canada: Part IV, Vol. 124. Ontario, CA: NRC Monograph Publishing Program. Accessed February 20, 2013 at http://books.google.com/books?id=lt0n1ga8sr0C&pg=PA46&lpg=PA46&dq=parasite+brosme+brosme&source=bl&ots=FNttWMXF03&sig=5CFBb8xt4ymNBuvTiv3xBTJijAs&hl=en&sa=X&ei=7_kkUdvpEIjn0gHu5IG4Dg&ved=0CCYQ6AEwBA#v=onepage&q&f=false.
Luna, S., E. Capuli. 2012. "Brosme brosme (Ascanius, 1772): Tusk" (On-line). Fishbase. Accessed February 20, 2013 at http://www.fishbase.org/summary/Brosme-brosme.html.
Matthews, J. 1927. Fisheries of the North Atlantic. Economic Geography, 3/1: 1-22.
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Nelson, J. 1994. Fishes of the World. Toronto: John Wiley and Sons.
Shackell, N., K. Frank, D. Brickman. 2005. Range Contraction May Not Always Predict Core Areas: An Example from Marine Fish. Ecological Applications, 15/4: 1440-1449.
Tyus, H. 2012. Ecology and Conservation of Fishes. Boca Raton, FL: CRC press.
Wootton, R. 1990. Ecology of Teleost Fishes. 29 W. 35th street, New York NY: Chapman and Hall.