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EP-4740731-A2 - FISH FARM WITH WORKING PLATFORM

EP4740731A2EP 4740731 A2EP4740731 A2EP 4740731A2EP-4740731-A2

Abstract

The present invention relates to a modular offshore fish farm comprising one or more closed net cages and a service unit, each closed net cage being supported by a buoyant body which is configured for floating in a body of water, wherein each closed net cage is configured for moving vertically in a body of water relative to the buoyant body, each buoyant body comprising a number of buoyant elements, where each buoyant body comprises connecting means for connecting to an adjacent buoyant body, the buoyant bodies providing a working platform between the closed net cages, where each closed net cage comprises a suppressing device.

Inventors

  • MATRE, Arne

Assignees

  • Westcon Yards As

Dates

Publication Date
20260513
Application Date
20221123

Claims (15)

  1. A net cage (2) for a modular offshore fish farm (1), - wherein the net cage (2) is supported by a buoyant body (3) which is configured for floating in a body of water (W), - the net cage (2) is a closed net cage, - wherein the closed net cage (2) is configured for moving vertically in a body of water (W) relative to the buoyant body (3) by changing the buoyancy of the closed net cage (2) by changing the amount of water being inside the closed net cage (2), characterized in that - each closed net cage (2) comprises a suppressing device (10) for suppressing fish inside the net cage (2).
  2. The closed net cage (2) for a modular offshore fish farm (1) according to claim 1, wherein the closed net cage (2) comprises a center column arranged vertically within the closed net cage (2), wherein the suppressing device (10) is arranged moveably along the vertically arranged center column.
  3. The closed net cage (2) for a modular offshore fish farm (1) according to claims 1 or 2, wherein the suppressing device (10) is moved from the lowermost position near the bottom of closed net cage (2) to its uppermost position, where a transfer of fish from the closed net cage (2) to a vessel (V), or to another closed net cage (2) is carried out.
  4. The closed net cage (2) for a modular offshore fish farm (1) according to anyone of the previous claims, wherein the buoyant body (3) comprises a ballasting and deballasting system in order to be able to position the buoyant body (3) and/or the closed net cage (2) correctly in a body of water.
  5. The closed net cage (2) for a modular offshore fish farm (1) according to anyone of the previous claims, wherein the closed net cage (2) comprises a pumping and cleaning system connected to a pipe (16) for supplying fresh water and a pipe (17) for drainage of sea water from the closed net cage (2), wherein the pumping and cleaning system is arranged in the buoyant body (3), wherein the pipe (16) is connected to one or more pumps (22) and one or more filters (23), wherein the pipe (17) is connected to at least one pump (24) and at least one filter (25, 26).
  6. The closed net cage (2) for a modular offshore fish farm (1) according to anyone of the previous claims, wherein the suppressing device (10) comprises - a number of ribs (11) extending between an inner center ring (12) and an outer ring (13), - a net (14) extending between two adjacent ribs (11), wherein the net (14) is configured to fish passing through a plurality of meshes of the net (14), wherein the net (14) is configured to be moveable radially inwards to provide an opening (O), wherein the inner center ring (12) is configured to move along the vertically arranged center column.
  7. The closed net cage (2) for a modular offshore fish farm (1) according to claim 6, wherein each of the ribs (11) is provided with at least one rope or wire, where two adjacent ribs (11) forms an adjustment system for the net (14), to move the net (14) between the inner center ring (12) and the outer ring (13).
  8. The closed net cage (2) for a modular offshore fish farm (1) according to claim 6 or 7, wherein a winch system is connected to each of the inner center ring (12) and the outer center ring (13).
  9. The closed net cage (2) for a modular offshore fish farm (1) according to anyone of claims 6 to 8, wherein the net (14) is water and air impermeable over at least a part of its longitudinal length.
  10. The closed net cage (2) for a modular offshore fish farm (1) according to anyone of claims 2 to 9, wherein the suppressing device (10) is arranged to be rotated about the center column provided in the closed net cage (2), through a rotating system.
  11. The closed net cage (2) for a modular offshore fish farm (1) according to anyone of claims 2 to 10, wherein the center column is provided with a plurality of adjustable openings and/or air nozzles provided along a longitudinal length of the center column, the plurality of adjustable openings and/or air nozzles being connected to an oxygenation system through one or more pipes or hoses.
  12. The closed net cage (2) for a modular offshore fish farm (1) according to any one of the previous claims, wherein the closed net cage (2) comprises at least one chute (7), duct or channel for transporting fish, wherein the closed net cage (2) is arranged with a closeable opening adapted, when the closeable opening is in the opened position, to guide fish from the closed net cage (2) via the chute (7) to a vessel (V) or another closed net cage (2).
  13. The closed net cage (2) for a modular offshore fish farm (1) according to anyone of the previous claims, wherein the closed net cage (2) and buoyant body (3) comprises a guiding and locking system, wherein the guiding and locking system allows the closed net cage (2) to be moved relative the buoyant body (3) and thereafter to be locked in the desired position.
  14. A modular offshore fish farm (1), wherein the modular offshore fish farm (1) comprises: - two or more closed net cages (2) according to anyone of claims 1 to 13; wherein each buoyant body (3) comprises connecting means for connecting to an adjacent buoyant body (3).
  15. The modular offshore fish farm (1) according to claim 14, wherein the modular offshore fish farm comprises a service unit (S).

Description

TECHNICAL FIELD The present invention relates generally to an offshore fish farm, and more particularly to a modular offshore fish farm comprising a number of closed net cages and corresponding buoyant bodies. BACKGROUND Aquaculture is a fast-growing global industry. The conventional fisheries are declining dramatically and the seafood needed in the future will, to a greater extent, have to be produced by aquaculture. However, in recent years, more challenges have arisen for this industry to be faced with. For the farming of salmonoids, this relates to, among other things, the treatment of fish infected with crustaceous parasites like salmon louse, the escape of fish from floating farming cages, diseases due to viruses, bacteria and parasites, so-called "genetic contamination" of wild populations of salmonoids, and emissions of waste products from the cages into recipients. These challenges especially relate to the farming of fish in conventional floating cages allowing flow-through of water. Such open cages are constituted by a net which forms a closed enclosure for fish in particular, and which is kept afloat by means of a surrounding buoyancy system. Closed farming cages are known within the art. These are formed of a tight cloth material which forms a closed enclosure for aquatic organisms such as fish. To ensure that the water exchange rate is sufficient for maintaining a minimum oxygen level in the water within the cage, it is common to pump in so much water that the water surface inside the cage is higher than the water surface outside the cage. Thereby the pressure within the cage is larger than the ambient pressure and water will flow out of the cage through formed openings. This will subject the buoyancy system of a closed cage to larger forces than the buoyancy system of an open cage of the same size. In addition to keeping the actual cloth or net of the cage afloat, the buoyancy of the buoyancy system must be dimensioned for holding the amount of water within the cage that is above the water surface of the surrounding water. This water constitutes a considerable mass. In addition, this water has a moment of inertia which causes the wave influence on the buoyancy system to be greater than in an open cage where the wave motion passes substantially unobstructedly through the buoyancy system and into the cage. Other have proposed another rigid semisubmersible fish farm for unshielded sea areas, which contains two buoys that are connected by vertical and diagonal brackets. Cages of the fish farm are fully submerged in the sea to avoid large wave loads near the water surface, and an underwater air bag is designed to provide air. It should be noted that this concept uses the conventional gravity cage, which relies on bottom ballasts to maintain the volume. Such cages encounter bigger deformation in the high-speed water flow in an unshielded area than in a shielded area. This could threaten the health of fish. In addition, there are also challenges with the use of the underwater air bag. A boat-like fish farm has also been proposed, where the boat-like fish farm has a single point mooring system working as a weather vane. The fish farm may rotate around a head structure in various environmental directions. Such a system can increase the spread of waste of fish resources and reduce the likelihood of infection. However, the proposed concept faces the following challenges. As the weather vane system allows the system to orient toward water flow and wave directions in most environmental conditions, in this boat-like fish farm downstream cages are subjected to less water exchange than upstream cages for the reason that multiple cages are arranged in a row adjacent to each other, i.e. at small distances in boat-like fish farms. Therefore, levels of dissolved oxygen of the downstream cages will be lower, than in upstream cages, and the amount of waste increases, which may seriously affect the health of fish. In order to improve water exchange, dynamic positioning systems have been proposed to orient the fishery at an angle in relation to water flows, but this significantly increases energy consumption as well as operational and maintenance costs. Thus, new configurations of marine fish farms, especially of fish farms in deep seas and high seas, are constantly emerging at present. However, each new fish farm system typically comes with its own problems and/or challenges, such as low sea use, high construction and maintenance costs, and being unfriendly to the environment, to mention a few. NO 338238 B1 relates to a buoyancy element for constructing a modular buoyancy system for a circularly shaped net cage, the buoyancy element including a cage side, an opposite straight long side, coupling sides between the cage side and the straight long side, and the cage side being curved, following the periphery of the net cage. WO 97/38573 A1 relates to an aquaculture system for growing aquatic animals such as fish and cr