Lumpfish fry hatch from a lump of eggs defended by the males for two months. They grow up in kelp forests and tend to hide on seaweed leaves where they hold on fast using a suction disc. Once they are sexually mature (after one to two years and weighing 120-200 grams), they swim out into open seas. They eat plankton for a period of two to four years in open waters, before swimming back to the coast to spawn. The male finds a suitable area in shallow waters for the lumpfish to spawn (up to one seventh of their body weight). The fertilised eggs are sticky and form a lump of eggs that attach to rock or stones on the seabed. The male defends the lump of eggs constantly, without eating or moving much until the larvae hatch. There is little knowledge of the lives of lumpfish once they are pelagic. Most probably, they live in deep waters (50-150 metres) and eat crustaceans and jellyfish.
Using lumpfish as cleaner fish in cages allows for a reduction in mechanical and medicinal delousing for salmon. Use of lumpfish is a gentle method of delousing salmon, eliminating environmental problems involved in the use of medicinal delousing agents. Controlling salmon lice by using cleaner fish is a goal for many companies in the industry, and the production of lumpfish and ballan wrasse is a growing industry. It is most common to add lumpfish to the cages at a ratio of 3 to 10 percent of the number of salmon. The farther north, the fewer cleaner fish are necessary, as salmon lice do not reproduce as easily in colder waters.
Photos by Finn Refsnes.