The present invention relates to fish rearing units, particulary a device according to the introductory part of patent.
Rearing fish in rearing units located in the ocean can be subject to undesirable changes in the environment, such as the flourishing of algae or jellyfish, and oil spillage. These occurances have shown to be an expensive problem for the rearing trade. So far fish farmers have in such cases had two options for preserving the value of the fish in the rearing plant:
1) slaughtering of the fish stock,
2) relocating the plant in a different area.
Both theses methods have been unsatisfactory for the fish farmer due to the large economic losses incurred. On the market today, there are closed PVC-rearing units where the water is pumped up from deeper layers. These units utilize the principle of transporting clean water up to the fish, and keep it separated from the environment, using a unit with a closed PVC-cloth.
There are also other known solutions where the rearing unit is lowered, with the floating ring/cage using air-filled, closed rooms in the floating ring. This is stated in NO patent publication 150,741, GB patent publication 2,008,912, DE patent publication 2.713.268, SE patent publication 458,088. Common to all these publications are the feature that both the rearing unit and floating ring should be lowered. The fish farmers thus cannot use existing investments in traditional rearing plants.
In order to hinder the spread of oil spillage, there exist oil bilges which suck up the oil, however, this is too expensive to have on each plant. The oil bilge does not suck up all surface oil. There will thus always be a thin film left on the sea surface, and this film is pollutive for fish Dumping at the surface. Furthermore, the effect of the oil bilge will be less if there are waves higher than 2-3 m.