Living up to its name, the lumpfish (Cyclopterus lumpus) has scaleless skin with a bumpy ridge down its back (which is actually a modification of the first dorsal fin) and rows of knobby protuberances, called tubercles, down each side. On the underside of its body its ventral fins have been changed into a round sucker disc. The lumpfish is a bottom dwelling creature, preferring rocky areas where it can attach itself by this sucker. It also will sometimes attach itself to floating masses of seaweed. The sucker disc is an important adaptation for, while it is capable of short bursts of speed by using its tail, this ungainly fish is a very weak swimmer. By attaching itself to something with the disc it avoids being carried off by currents.
Coloration in lumpfish varies widely. Young individuals usually match their surroundings in color and are green or yellowish. Adults may be mottled blue, olive, brown, or gray, with the males more vividly colored than the females. Also, the males turn red during breeding season.
Adult lumpfish are usually 14 to 16 inches long and weigh 3 to 6 pounds, with the females generally larger than the males. Females have been known to get up to 24 inches long and weigh up to 20 pounds. They prefer shallow coastal waters of the North Atlantic and range from the Gulf of St. Lawrence to New Jersey in the west and from northern Norway to Portugal in the east Atlantic.
Starting in February and continuing until mid-June the lumpfish come into the shore waters to spawn. The female will lay from 80,000 to over 100,000 eggs in a spongy mass which sinks and adheres to rocks. Once her eggs are laid the female moves out into deeper water leaving their care and protection to the male. The male lumpfish will stand guard over the eggs until they hatch, protecting them from predators, even those larger than himself, fanning them with his fins to aerate them and prevent silt build-up. He will not eat during this time, nor will he leave the nest except to scare off an intruder.
When the larvae hatch they will be about 1/4 inch long and resemble tiny tadpoles. They are soon able to attach themselves to seaweed. By the end of its first year it will be one to two inches and will reach maturity in about its third year.
Lumpfish eat worms, small crustaceans and fish, and jellyfish. They are not considered edible, but in some areas their eggs are harvested, dyed (perhaps to resemble sturgeon roe), and sold as caviar.