The fish needs high water temperatures during hatching. As it grows, it needs cooler water and access to concealment. Keeping the necessary cover clean in a breeding tank is important and can be resource-demanding.

Another problem is the risk of infection in the hatching phase: Under natural conditions, the wrasse builds small nests for its eggs on the seabed. In the laboratory, mats of artificial weed are used, in which the eggs thrive, but so do bacteria.

"When the eggs have hatched, bacteria growth must be kept under control. We still don't know the best way to do this without damaging the eggs and fry," says Gunvor ie.

At the same time, tiny crustaceans are being studied as potential "baby food". The researchers hope that if the initial feeding is optimal, the fish will grow more rapidly in their first year of life. Their diet consists of tiny zooplankton called rotifers. Because several types of rotifers (commonly known as wheel animals) exist, a laborious, systematic hunt is in progress for the best alternative. Researcher Gunvor ien is convinced that the young wrasse will survive if she can find rotifers of the right quality.

If she is right and the studies are successful, the biological cure for salmon lice will be welcomed by the aquaculture industry, the authorities and the environmentalists - not to mention the salmon themselves.

sintef