PROJECT RESEARCHES WELFARE OF CLEANER FISH

Project researches welfare of cleaner fish. Lumpfish are cleaner fish used to fight salmon lice. The Norwegian Rensvel project conducted by Nofima aims to find ways of gauging cleaner fish’s welfare and what it needs to thrive and stay healthy.

Companies that produce lumpfish must therefore know what the fish need to thrive, grow and stay healthy – basically: the right feed, enough space, good water quality and minimum stress.

Access to food is important. Lumpfish are not strong swimmers and need to rest. They do this by attaching themselves to the tank wall using a ventral suction plate. In other words, good feed and the right environment are key for lumpfish to “thrive” at work.

“Because lumpfish like to sit on the tank wall and are not fast swimmers, feed needs to fall down near the tank walls. Most commercial farms use dispensers located in the centre of large tanks, which may be too far away for young lumpfish,” says senior scientist Ingrid Lein.

It has been claimed that lumpfish that grow rapidly become aggressive and “bully” smaller fish. Lumpfish are therefore usually graded by size many times before being transferred to pens in the sea. The Rensvel project has shown that ungraded lumpfish can live close to their neighbours without any bullying.

“To avoid bigger fish bullying the smaller ones, there must be enough feed for everyone. In addition, the feed pellets must be large enough for the largest lumpfish and small enough for the smallest,” explains Lein.

Lumpfish like clean, well-oxygenated, fast-moving water. Because they need to rest every now and again, it is important to provide enough space in the tank for all the fish to be able to find a place to rest.

Crowding is not a problem in itself, as long as the fish get enough of the right food, can find a place to rest and have good water quality.

“Lumpfish are social, thrive in groups, and are not plagued by disease,” says Ingrid Lein.