Cyclopterus is a genus of marine ray-finned fish belonging to the family Cyclopteridae, the lumpsuckers or lumpfish. Its only species is Cyclopterus lumpus, the lumpsucker or lumpfish. It is found in the North Atlantic and adjacent parts of the Arctic Ocean, ranging as far south as Chesapeake Bay (rare south of New Jersey) on the North American coast and Spain (rare south of the English Channel) on the European coast. The species has been reported twice in the Mediterranean Sea, off Croatia in 2004 and Cyprus in 2017.
Cyclopterus is a compound of cyclos, meaning 'ring', with pteros, which means 'fin'. This is a reference to the pelvic fins being modified into a suction disc. The specific name lumpus is derived from the Anglo-Saxon lump and the fish was callued Lumpus anglorum by Gessner in 1558. This seems to refer to the dorsal fin being embedded in the thick and tubercular skin on the back, creating the impression of a hump.
Cyclopterus is sexually dimorphic with females reaching larger sizes than the males. Males typically reach 30–40 cm (12–16 in) in length while females can typically grow up to 50 cm (20 in) in length and 5 kg (11 lb 0 oz) in weight. The largest specimen recorded measured 61 cm (24 in) in length, and 9.6 kg (21 lb 3 oz) in weight. In the brackish water of the Baltic Sea, it usually does not surpass 20 cm (8 in). The body is ball-like. It has a knobbly, ridged back and three large bony tubercles on each flank. Its pelvic fins form suction discs which it uses to attach strongly to rocks or other surfaces. The head and the pectoral fins of males are larger than those of females. It has a jelly-like layer of fat under the skin. Its colour is highly variable; bluish, greyish, olive, yellowish or brownish. Mature males turn orange-reddish during the breeding season.
Cyclopterus spend the first few months following hatching in tidal pools, or in association with floating seaweed clumps. As they grow they migrate out into open water far from land where they live in the pelagic zone feeding upon gelatinous zooplankton, fish eggs and small crustaceans. When they reach maturity they will migrate to coastal areas in spring to breed. During the breeding season, males change colour, taking on a reddish/orange colouration. The population spawns over many months with spawning fish being caught in Iceland from March until August. Females which have spawned during the previous year tend to return to the same area when spawning again. They will also return at a similar time of year i.e. individuals which spawned early and late in the season will return to spawn early and late in the season the following year. A single female will lay 50,000–220,000 eggs which are laid in two batches of roughly equal size 1–2 weeks apart. The eggs are between.mw-parser-output.frac{white-space:nowrap}.mw-parser-output.frac.num,.mw-parser-output.frac.den{font-size:80%;line-height:0;vertical-align:super}.mw-parser-output.frac.den{vertical-align:sub}.mw-parser-output.sr-only{border:0;clip:rect(0,0,0,0);clip-path:polygon(0px 0px,0px 0px,0px 0px);height:1px;margin:-1px;overflow:hidden;padding:0;position:absolute;width:1px}2.2 and 2.5 millimetres (11⁄128 and 13⁄128 in) in diameter and the ovary can account for up to one third of the weight of the female fish before spawning.
The female will lay the eggs in a nest area pre-selected by the male, which will usually consist of a rocky outcrop or boulders on the seabed. The nest is in relatively shallow water (<10 metres (33 ft)) and may even be in the intertidal zone. The male also guards and cares for the eggs by fanning them with his fins during the month-long incubation period.
Several aspects of their biology (i.e. lack of a swimbladder, its pelvic suction disc) led some to believe that they were a bottom dwelling species. Lumpfish are frequently caught in pelagic fishing nets, however, capture in bottom trawls is also common. An investigation using electronic data-storage tags attached to the fish have confirmed that, at least during its breeding migration, this fish will spend time associated with the sea bed, and also some time in the pelagic zone. As the fish came close to breeding, they began to spend a greater amount of time in the pelagic zone. With the lack of a swim bladder, the fish were able to make rapid movements through the water column, moving between surface waters and depths of over 300 m (980 ft) within one day. Data from research surveys and data-storage tags show that adult lumpfish alter their behaviour between night and day with the fish spending more time in the pelagic zone at night and found associated with the seabed during the day, the reasons for this are unclear. The current understanding is that after the juveniles leave coastal areas, they adopt a pelgic lifestyle, inhabiting the upper 50-60 m of the water column. It is only when they begin their return migration to the coastal areas for spawning that they begin to spend time close to the seafloor.
Juvenile lumpfish exhibit biofluorescence, that is, when they are illuminated, light absorbed by the organism is remitted in lower energy wavelengths. The light reemitted by lumpfish appears green to the human observer and peaks at 545 and 613 nm. The greatest intensity is along the tubercles of the high crest and the three longitudinal ridges. The purpose of this biofluorescence remains unclear and it is also not known if this is also exhibited by adult lumpfish.
Cyclopterus populations in both Iceland and Norway, the population is monitored using data from scientific surveys and is currently above the long term average and considered to be healthy. In Greenland, no survey data is available and data on fishing effort and landings are monitored. The time series is short for this population however appears to be stable. The population in Canada appears to be depleted and the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) has classified this as threatened. There is a lack of data to reliably assess the abundance of lumpfish in the North Sea or Baltic Sea thus the population status of this area is unknown. The fishery in Greenland and Norway was certified by the Marine Stewardship Council in 2015 and 2017 respectively with these certifications being valid for 5 years. The fishery in Iceland was certified in 2014 but this was suspended in 2018 due to issues surrounding bycatch but regained certification in 2020.
