Cusk (Brosme brosme)

Cusk
(Brosme brosme)
Photo: NMFS Northeast Region

Did You Know?

· Cusk is the only fish in its genus Brosme.

Status
ESA Candidate Species - throughout its range
ESA Species of Concern - Atlantic-Gulf of Maine

Taxonomy
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Ophidiiformes
Family: Lotidae
Genus: Brosme
Species: brosme

Species Description
The cusk is a very unique species of fish and the only one in its taxonomic genus of Brosme. Cusk can be up to 3 feet (1 m) in length and weigh up to 20 pounds (9 kg). They are characterized by a single chin "barbel" and single dorsal fin. Their upper body ranges in color from a light grey with hints of brown to a dull reddish brown that transitions to a dirty white on the belly.

Cusk are relatively slow-growing and late-maturing. Fifty percent of fish mature at approximately 1.5 feet (.5 m) in length when they are about 5 to 6 years old. Females generally mature later than males. The maximum age of this species is believed to be greater than 14 years.

Cusk spawn in spring and early summer. Eggs initially rise to the surface where hatching and larval development take place. Juveniles move to the bottom at 2 inches (5 cm) in length and become sedentary and solitary.

The cusk diet consists primarily of various species of crustaceans, fishes, and echinoderms. Cusk are solitary or occur in small groups.

Habitat
The cusk is a deep water species found in rocky, hard bottom areas to a depth of 100 meters (328 ft) and water temperatures of 30 to 50°F (1-10°C). In the United States, cusk have been found to be distributed primarily in deeper waters in the central portion of the Gulf of Maine.

Distribution
Cusk occur in the Northwest Atlantic from New Jersey to the Strait of Belle Isle and on the Grand Banks of Newfoundland. They are found rarely at the southern tip of Greenland. In the Northeast Atlantic, they occur off Iceland, in the northern North Sea, and along the coast of Scandinavia to the Murmansk Coast and Spitzbergen, Norway.

Population Trends
A declining population trend has been evident since the late 1960s. All abundance indices remained at or close to record-low levels from 1985 through 2002. The NMFS Northeast Fisheries Science Center biomass index for cusk was near zero in 1998 and is the record low. In the early 1970s, individual fish weight averaged 7 lbs (3 kg) but declined by 50% to 1.5 kg (3 lbs) through the late 1990s. Landings and survey indices have dropped considerably from 1984 to 2004. The ratio of landings to biomass estimates has been increasing since 1986, which implies increased exploitation over time.

The catch per unit effort from 1970-2001, or just over 3 cusk generations, declined by about 90% while population estimates for cusk greater than 20 inches (0.5 m) in the same time frame demonstrated a 96% decline (Committee on the Status of Endangered Wildlife in Canada (COSEWIC) 2003). Furthermore, cusk are caught in an increasingly smaller area on the Scotian shelf each year (COSEWIC 2003).

Threats
Commercial fishing is the prime factor for the decline in cusk abundance. Fisheries use four principal gears to catch cusk:

line trawl
otter trawl
gill net
longline

Cusk are often taken as "bycatch" in longline fisheries directed at Atlantic halibut, cod, haddock and pollock. Cusk landings were relatively stable at 1,700 metric tons per year in the 1960s and early 1970s. Landings increased to about 2,360 metric tons in the late 1970s to mid-1980s, fluctuated in the late 1980s and early 1990s between 1,500 and 2,400 metric tons, and then declined to less than 500 metric tons in 1998. The 1998 U.S. landings were about 355 metric tons and accounted for 72% of the total harvest. Canadian landings in 1998 were 140 metric tons. Total U.S. landings in 2004 were down to about 79 metric tons. Mean length has declined from 2 feet (0.6 m) during 1964 to 1987 to about 19 inches (0.5m) during the period of 1988 to 1998, indicating excessive fishing. The slow growth and late maturation of this species increases the risk of over-exploitation.

Conservation Efforts
In the United States, the cusk fishery is not presently managed. Fishing was unrestricted in Canada until 1999 when limitations were established for landings in the Scotia-Fundy region. In 2004, NMFS made cusk a "species of concern". Species of concern status is meant to draw proactive attention and conservation action to a species from relevant state and federal managers and partners. A special funding opportunity is available to improve the status of species of concern. Species of concern status does not carry any procedural or substantive protections under the ESA.

Regulatory Overview
Due to concerns over the status of this species, NMFS initiated a status review of this species in March, 2007. This status review will be used to determine whether listing of cusk as a threatened or endangered species under the Endangered Species Act is warranted.

Key Documents
(All documents are in PDF format.)

Title	Federal Register	Date
Notice of Initiation of a Status Review under the Endangered Species Act (ESA)	72 FR 10710	03/09/2007
Species of Concern Fact Sheet: Detailed	n/a	05/11/2009
Fact Sheet Highlights	n/a	07/22/2009

More Information

NMFS Northeast Fisheries Science Center Status of Cusk Fishery Resources off the Northeastern U.S.