Cusk (fish)

Species of fish

The cusk or tusk (Brosme brosme) is a North Atlantic cod like fish in the ling family Lotidae. It is the only species in the genus Brosme. Its other common names include European cusk, and brosmius.

It is easily distinguished at a glance from other cod like fish, as it has only one dorsal fin. Also characteristic of the fish is the nature of its dorsal, caudal, and anal fins; they are continuous at the base, but separated by very deep notches so that they are obviously distinct. Moreover, the caudal fin is evenly rounded. It is variable in color, from slate to reddish brown above, and paling to gray on the lower sides and underneath. Older fish are usually plain colored, while the young often have transverse yellow bands on their sides. Their maximum length is about 4 ft (120 cm) and top weight is about 45 lb (20 kg). The IGFA world record stands at 37 lb 14 oz (17,20 kg), caught by Anders Jonasson outside Sørøya in northern Norway.

It is distributed on both sides of the North Atlantic, mostly in moderately deep water. On the North American coast, it is regularly found southward to Cape Cod and occasionally off New Jersey. Its maximum range covers most of the North Atlantic, including the waters around Iceland and the Norwegian coast. Cusk show little genetic differentiation over large distances, except where populations are surrounded by deep water areas, namely on the Mid Atlantic Ridge and the Rockall Bank. This suggests deep water areas are barriers for adult movements, and though they have pelagic eggs and larvae, dispersal during early life stages is not effective over long distances. Cusk are a food source for many other organisms, so the toxins they accumulate over time directly affect any other organism that consumes them, including humans. Studies conducted in Western Norway, Central Europe, and the Mediterranean have shown that mercury concentrations within fish are highest in wild marine fish, which sometimes exceed food safety guidelines of 500 μg/kg, whereas wild freshwater and farmed fish have less mercury within their system. The status report identified that catches of cusk in the DFO summer bottom trawl survey had declined by roughly 90% from 1970 to the late 1990s. A landings limit of 1000 mt was put in place in 1999 in the 4X North American Fisheries Organization area and was further restricted to 750 t and expanded to include the 4VWX5Z NAFO areas in 2003. Cusk are still commonly caught as bycatch in the longline and lobster fisheries and can be found in supermarkets in Atlantic Canada despite its threatened status. A study that was conducted in the Gulf of Maine region showed that the conservation status of cusk was partly dependent on future greenhouse gas emissions. Higher emissions showed greater habitat reduction, as much as 80% by the end of the century. Cusk is a US National Marine Fisheries Service species of concern, which are those species about which the National Oceanic and Atmospheric Administration, National Marine Fisheries Service, has some concerns regarding its conservation status and current threats, but for which insufficient information is available to indicate a need to list the species under the Endangered Species Act. On March 9, 2007, the National Marine Fisheries Service announced the initiation of a status review to determine whether the species warrants listing under the act.