FLAT FISH CAGES

The need to extend and diversiby the Norwegian aquaculture industry and a growing demand to store live seafood has led to the development of a flat-bottom net cage.

This technology has improved the first hand value of seafood and motivates a better utilisation of the coastal resources. It provides practical working conditions for the emergin sea-based halibut farming in Norway and is now being utilised abroad for species such as flounder and grouper.

An aluminium frame covered with a taut net supports the bottom of a traditional net. The bottom area is 180 m2 and the frame consists of 12 pipes connected with 12 bends. The depth of the bottom is modify pneumatically by inflating a central positioned cylinder. The bottom is kept horizontal at all times and elastic ropes eliminate the vertical movement.

RESULTS

About 14 tons (e.g. turbot, plaice or lemon sole) can be stored or raised in each cage. The rigid, but elastic construction enables the care takeers to inspect the fish utilizing waders. This cage is now in use in several areas:

• Receiving newly-caught wild cod, where a flat bottom is requiered for proper restoration and acclimatation prior to transfer to traditional net cages.

• Storage of wild caught species without a gas bladder e.g. plaice, lemon sole, halibut, wolfish and turbot.

• Rearing of halibut and spotted wolfish.

• Storage and feeding of sea crustacians (e.g. king crab).

• Storage and feeding of sea urchin.

• Intermediate storage of fish before slaughter.

CONCLUSION

This cage system, being operated by compressed air, eliminates most of the hard labour in today's sea based aquaculture.

The bottom ensures that inspection, grading and vaccination can be performed as if it were land based.