Aquatraz semi closed fish cage
| no escape | reduced mortality | doubled # fish | few lice | good HSE | improved fish health | improved bottom line |
Over the course of three years, Aquatraz, the semi closed fish cage, has been developed from concept to commercial product. Four fish cages from three development generations have thus far been launched. They have accumulated three years of operation and produced 5,000 tonnes of salmon. Further results from operation of the Aquatraz G3 over the summer 2020 will be incorporated in the final design phase for the fourth and last generation Aquatraz. Already in the summer 2020 Aquatraz G4 will be available for fish farmers that have not been part of the development project, to declare their interest and join the final phase of delivery of G4 cages in the autumn of 2021.
The raiseable steel structure with wide walkways and handrails provides great working conditions without heavy lifting. Aquatraz has a design life of 20 years with low operating and maintenance costs.
The lifting system and the extraction of fish in the lower part of the fish cage make delivery of salmon safer and faster, while safeguarding the welfare of both man and fish. When the fish cage is lifted, the volume within the cage is reduced and the salmon instinctively searches for deeper water. As it reaches the bottom of the net it is pumped into a well boat.
The lifting system provides easy access to the inside and outside of the fish cage, which facilitates washing, disinfection and maintenance of the cage on site. As a result of the lifting system, the cage can also be raised and towed to a new location without opening the frame mooring.
The water replacement system and the deep lice skirts provide a positive aquatic environment in the cage. Oxygen-rich water is pulled in from lice and algae-free water depths and circulated in the cage at a replacement rate of about 3600 m3/min. The complete volume is replaced every 20. minutes. As in closed fish tanks, the salmon in Aquatraz opt to stay in the induced stream and the training intensity can be optimized by adjusting the circulation speed according to current, temperature and fish size. This is believed to improve fish health, increase growth rate, lower feed factor, improve colour and produce firmer fish fillets.
In Aquatraz G1 and G2, there was few lice compared to conventional net pens, despite the fact that the net pens were fitted with lice skirts and a Midt-Norsk ring. For Aquatraz G3, further reduction in lice is expected as a result of the lice skirt being increased from 8 to 18 meters deep.
Safeguarding against escape and secured supply of large quantities of water ensured that the first three cages have received dispensation for the maximum number of fish to be increased from 200,000 to 400,000 salmon per cage. Furthermore, an exemption has been granted to increase the density from 25 kg/m3 to 45 kg/m3
The latest Aquatraz, launched in May 2020, have implemented a total of 18 meter of lice skirt. The top 8 meter in steel and the additional 10 meter in tarpaulin. This is done in preparation for the fourth and final generation Aquatraz, which will have an even longer and rigid lice skirt.
The second generation Aquatraz – G2, has a new electric lifting system that allows lifting and lowering without relying on energy supply from a boat. It has wider walkways with space for storage containers and several other improvements that is still part of the fish cage in newer generations
|Key figures||Aquatraz G3||Aquatraz G4|
|Circumference||160 m||160 m|
|Height||23,6 m||> 25 m|
|Volume||50.500 m³||60.000 m³|
|Lice skirt depth||18 m||≥ 22,5 m|
|Delivery system with telescopic pipes||Yes||Yes|
|Water circulators||4 pc||≥ 4 pc|
|Energy consumption circulators||25 kW||≥ 25 kW|
|Exchange rate water||3600 m³/min||≥ 3600 m³/min|
|Replacement of water volume||every 20. minutes||every 20. minutes|
|Storage containers||4 pc a 10 fot||4 pc a 10 fot|
|Emergency generator with automatic start||Yes||Yes|
|Maximum individuals (disp)||400.000||TBA|
|Maximum fish (disp)||45 kg/m³||TBA|