Every job has problems, large and small. Many of them can be solved quickly, whilst others require more staying power. Salmon farmers in the Norwegian fjords have a problem, which is only a few millimeters long, yet it certainly keeps them on their toes: the salmon louse.

The small parasite attaches itself to the skin of farmed salmon, where it causes lesions and, in the worst case, results in death. The farmers therefore place a protector alongside the salmon – the lumpfish, which eats the lice. To meet the demand for lumpfish, many salmon farmers breed them in special tanks made of Polystone® G. The tanks are manufactured by Plastsveis AS, a Norwegian company specializing in onshore fish farming. The lumpfish grow in the tanks until they are big enough for parasite patrol.

Trouble-Making Salmon Lice
The salmon are reared in floating net enclosures in the Norwegian fjords. This makes controlled farming possible in natural waters and offers an alternative to overfishing in seas around the world. At the same time, this kind of farming, which is also known as aquaculture, solves the problem of sufficient food for the world’s ever-increasing population.

A salmon will spend two to three years growing in the enclosures until it weighs four to five kilograms, the right size for consumption. Constantly causing trouble for salmon farmers is the salmon louse, which occurs naturally in Norwegian waters. Conditions in the net enclosures are conducive to lice infestations because the density of fish is higher than in natural surroundings. More and more farmers are turning to the lumpfish to protect the farmed salmon and keep them healthy despite the parasite. The small, shiny, greenish fish devours the lice on the salmon, thus providing a gentle and effective method of pest control.

Lower Costs, Healthier Fish
This parasite-eater, which belongs to the biological family Cyclopteridae, has many advantages for the farmers. The lumpfish reduces the use of conventional pesticides as well as the amount of sick salmon requiring medicines. This promotes the well-being of the creatures, supports their growth and reduces both health risks and environmental risks. It results in lower costs and healthier fish for the farmers.

It is no wonder that the demand for lumpfish in Norway has risen sharply in recent years. The salmon enclosures have a diameter of approximately 50 meters and are between 20 and 50 meters deep. A maximum of 200,000 salmon and lumpfish can swim together in each enclosure. This gives each creature plenty of space as the density of fish is strictly limited. Lumpfish account for between eight and ten percent of each enclosure. This means that approximately 40 million lumpfish are needed every year in Norway. This demand cannot be covered by natural fishing. Selective breeding is needed.

Fit for Parasite Duty
This is why many Norwegian salmon farmers rely on tanks made of Polystone® G from Röchling for breeding lumpfish. The lumpfish grow in the specially designed tanks in separate onshore breeding stations until they are fit for parasite duty in the fjord. The tanks are made by the Norwegian company Plastsveis AS. Polystone® G is very easy to process and weld, so it can be used to manufacture tanks to customer specifications. When making tanks specifically for fish farming, it is always essential to consider the characteristics of the respective inhabitants. For instance, the lumpfish likes to withdraw to the walls of the tank to rest. This is why they must always be really clean. Polystone® G is very easy to clean, so it facilitates lumpfish breeding. The durability of the material also plays an important role, as the planned service life of the tanks is several decades. Plastsveis AS can therefore use Polystone® G to manufacture individual and durable tanks specifically for breeding lumpfish.


Matthias Heidemann
Röchling Industrial
Area Sales Manager
Phone: +49 5934 701-448

Photos © Nordland Renesefisk AS, Röchling