Lumpsucker

Fascinating facts about the Lumpsucker

• A female lumpfish can tip the scales at 5 kg (11 lb), while the biggest recorded individual weighed 9.6 kg (21 lb 3 oz) and measured 61 cm (24 in). Those dimensions dwarf the typical male, which usually tops out at 30–40 cm (12–16 in). Size differences show how females invest heavily in egg production, packing a third of their body weight into ovaries before spawning.
• When the breeding season arrives, males turn a vivid orange-red, a stark contrast to their usual camouflaged hues. The male guards a nest on a rocky outcrop in water less than 10 m (33 ft) deep, and his parental care includes fanning the eggs for a month, ensuring the next generation gets a safe start.
• Juvenile lumpfish glow green under blue light, re-emitting wavelengths that peak at 545 nm and 613 nm, especially along the tubercles on their backs. This biofluorescence is visible only when illuminated, and scientists still aren’t sure what purpose it serves.
• Lumpfish can zip between the surface and depths over 300 m (980 ft) in a single day, despite lacking a swim bladder. Tag data reveal they spend daylight near the seabed and drift into the upper 50–60 m (160–200 ft) at night, switching habitats as they migrate back to coastal spawning grounds. Their ability to move so rapidly challenges the old view of them as strictly bottom-dwelling fish.
• From 1977 to 2018, global lumpfish roe harvests ranged between 2,000 and 8,000 metric tons (2,200–8,800 short tons), fueling a caviar substitute industry. Iceland and Greenland now dominate the fishery, supplying over 95 % of the catch, while Norway and Canada have slipped back due to price drops and population drops. The shift shows how market demand and conservation status directly reshape a species’ commercial story.

At a glance

About the Lumpsucker

The lumpsucker, Cyclopterus lumpus, is a round-shaped fish cloaked in a thick, tubercular skin that gives it a knobbly, ridged back and three prominent bony tubercles on each flank. Females grow to about 50 cm and 5 kg, while males stay smaller at 30–40 cm, though the largest recorded individual reached 61 cm and 9.6 kg. Its pelvic fins have evolved into a powerful suction disc, allowing the fish to cling to rocks, boulders or even the hull of a boat. Colouration varies from bluish to brownish, with mature males flashing an orange-red hue during the breeding season. In the brackish Baltic Sea they rarely exceed 20 cm, but in the cold North Atlantic they roam waters as chilly as –1 °C, favouring temperatures between 4 °C and 12 °C. Juveniles linger in tidal pools and seaweed mats before adopting a pelagic lifestyle in the upper 50–60 m of the water column, feeding on gelatinous zooplankton, fish eggs and tiny crustaceans. As they mature they migrate to coastal shallows (<10 m) to spawn, where males guard the eggs in rocky nests while fanning them for a month. A striking, little-known trait of the species is its bio-fluorescence: when illuminated, juvenile lumpsuckers re-emit absorbed light as a green glow, peaking at 545 and 613 nm, especially along their tubercles and longitudinal ridges. The function of this glow remains a mystery, and it is unclear whether adults retain the ability. Despite lacking a swim bladder, the fish can dart rapidly through the water column, traversing depths of over 300 m in a single day and shifting between pelagic and benthic zones with the approach of the breeding migration. Their nocturnal habit of spending more time in the water column, contrasted with daytime seabed association, adds another layer to their enigmatic behaviour.

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