Device for farming of marine organisms, particularly fish.
The invention relates to a device as stated in the introductory part of claim 1 for farming marine organisms, particularly fish.
Fish farming in traditional net cages has inherent disadvantages. Firstly, the fish farming has caused contamination in different ways, thereby raising environmental problems. Particularly, problems connected with fodder residues and escaped fish, e.g. salmon, have been considerable and increasing. Secondly the fish of the net cages have been subjected to harmful influences from the environment, e.g. algae and jellyfish or other harmful organisms.
Thus there has existed a long time need for fish farming plants which are closed or which have a controllable communication with the environment.
This has prompted land based plants, with controlled exchange of water from and to an ambient watercourse or seaway or with complete or substantially complete recirculation.
Until to now, land based plants have not been profitable when competing with floating net cages.
As early as 1973, it was proposed to provide a receptacle for floating on water, to reduce the costs for providing a site and a land system. From US patent specification 3,709,195 (Tabb 1973) it is known to arrange inflatable bags on water, and add fry and fodder and oxygen. Such a system has not proved suitable for large scale fish farming.
Further, it is known to use closed net cages for fish farming. This prevents the escape offish and simplifies the supply of oxygen by self controlled circulation of water. However, the problems of fodder residuals, harmful entry of organisms or substances from the water are not solved in this way.
From US patent specification 4,252,081 (Smith 1981) it is known to use net cylinders as fish farming cages. This has reduced the problem of removal of fouling, but not the problem of isolation relative to the environment, e.g. to prevent infection.
To provide similar reliability as land based plants, it has been proposes to provide a completely closed plant, e.g. in the form of tubes. In US patent specification 4,044,720 (Fast 1977) there is described fish farming plant with floating box shaped containers where water is taken from a certain depth. However, such open containers have not been suitable for commercial fish farming.
It is also known to use tubes arranged in the water as fish cage, e.g. from WO application 80/01129 (Muller Fuega 1980) and from "Laks i rør" in Norsk Aquakultur 3/88. Such tubes have not proved suitable and competitive interms of investment nor operation.
The main object of the invention is, based on the technology described WO 80/01129 (Mueller Fuega) to provide a device for rearing marine organisms, which can be used in large scale operation.
There is a need for a device, which can accommodate up to approximately 20.000 m3 of water and which allows access of staff and equipment for operating the plant.
It is particularly important to have a fish farming receptacle which can be easily cleaned and which has low maintenance requirements.
It is also desirable to provide a device allowing the control of light and/or temperature, to provide optimum growth conditions for the fish. Further it is desirable to distribute the intake of fodder so as to achieve uniform weight increase of the fish.
A particular object is to provide an internal power supply for operating light, fodder supply, etc.
Additionally there are the general requirements for weather resistance and economy.
The invention is defined in claim 1. Claims 2-9 states particular features. The invention is suitable for farming of most kinds of breeding fish, both fatty and white fish. Claim 10 describes a method for manufacturing a container for a device according to the invention. A particular advantage of the invention is reduced fodder consumption. This reduction can be considerable and provide cost-benefit even with the investments needed for the closed plant according to the invention.
A further advantage is reduced contamination. With the novel device, the recipient will not have any input of residues, as has been the case with open fish farming plants. The invention eliminates the risk of escape and ensures that no breeding fish will go astray.
Correspondingly, the invention will provide protection against external damaging influences, be it from the weather or from organisms in the sea.
Further the invention will provide the opportunity to control the breeding conditions (light and temperature), to continuously achieve optimum breeding conditions for the fish concerned.
The invention will also provide better working conditions for staff, both on daily operation and maintenance.
Compared to land based plants, the invention will provide reduced investments.
The invention will be described in more detail in connection with the following examples.
The invention is illustrated in the drawings, in which
Fig. 1 shows schematically a side view of an ambodiment of the invention,
Fig. 2 shows a transversal section of the embodiment in Fig. 1, Fig. 3 shows a sectioned perspective view of a part of the embodiment in Figs. 1 and 2,
Fig. 4 shows a perspective view of an alternative end embodiment, with several access doors, while
Fig. 5 shows the utilization of a boat as working platform for erecting a container as shown in Figs. 1 and 2.
In Figs. 1 and 2 a system for breeding fish is shown with a receptacle 11 which is arranged to float partly submersed in the water in a suitable location, e.g. in a fiord or a bay at the coast. Such a receptacle can be used everywhere where there is sufficient sea depth, in lakes, river mouths, harbours and artificially sheltered parts of an ocean. The receptacle 11 of the embodiment is cylindrical with a horizontal axis 12, with a main part 13 formed by an assemblage of annular parts 14. Each annular part 14 can be assembled from 4-8 arched elements 15 with edge flanges 16 being joined to adjoining elements circumferentially and axially.
Each end of the receptacle 11 is closed by a conical end piece 17, 18. Such an end piece 17, 18 can be assembled from several sub pieces connected with bolts. In this way the receptacle 11 can be manufactured on an industrial base of smaller parts being transportable to the site of assembly, and also disassembled for moving and reassembly.
The end pieces 17, 18 each have an opening 19 at the end for the flow of water. In its most simple form, the receptacle 11 can be anchored so as to be subject to natural sea current. It can be anchored at one end so that it can sway.
The access of water can be controlled for different purposes. An important consideration is to avoid attack from contamination, algaes and other damaging organisms. This can be achieved by taking water from a substantial depth, eg. 100 meter.
The receptacle 11 can be operated in different ways: as stationary plant, with a fixed entrance 20 at one end wall, or as a rotating plant, with continuous or stepwise rotation. At stationary plants, the top of the receptacle can be provided with solar cell panels to supply electrical power for operating fodder distributing equipment and monitoring and communication equipment. In this case, it will also be convenient to control the light to affect the breeding conditions.
Rotating the receptacle can solve the problem of fouling. Thus the receptacle can be rotated around its axis at certain intervals, eg. 60°. The external side will then be easily accessible for flushing or scraping off fouling. The inner side of the receptacle 11 can be prepared for the current use, depending on the breeding fish and the operation. In Fig. 2 there is shown a floating platform 35 which can be used as a platform for staff, any power generator, light equipment and equipment for withdrawal of fish.
The receptacle 11 may have a diameter of 25 meters and the length of the main part can be 40 meters. The arched elements 15 may be manufactured of fibre reinforced plastic, which may have an integrated foam to provide buoyancy. To provide sufficient strength for plants intended for severe weather conditions, bracing rings may be incorporated between the rings 14.
Fig. 3 shows a bracing ring 21 with a trussed structure of an upper boom 22 and a lower boom 23 with T-profile, and intermediate diagonal members 24 all being assembled together by welding or other suitable means. The bracing ring 21 is arranged between rings assembled of arched elements 15, this structure being bolted along circumferential and axial joints.
Fig. 4 shows an alternative end wall 25 particularly intended for rotation of the receptacle 11. To provide access to the receptacle 11, four doors 26-29 are distributed around the circumference based on a 90° rotation between each operating position. Centrally on each end wall there is provided a supporting conical wall 30 with an end opening 31.
Fig. 5 illustates the assembling of a receptacle 11 at sea, using a assisting vessel 32. The vessel has a deck 33 extending bck from a forward pilot house, with a cargo hold 34 under the deck 33, for accommodating building elements, mainly arched elements 15. The arched elements 15 are arranged over the deck of the assisting vessel and are moved into the water after being joined. After placing the first ring 14 around the stern of the asssisting vessel, arched element 15 after arched element is added along the circumference and lengthwise, until a complete receptacle 11 is assembled.
The invention may also be prepared with a receptacle 11 which is open in one end. The requirement is the supply of sufficient water in the closed end to provide a flow of water through the receptacle and out of the open end, to prevent intake of undesirable water and organisms. Such a receptacle should have screens to keep the fish inside and respectively separated into groups of different size.
To reduce costs further, the invention can be realized in the form of an open tube with screens at the ends. Arranged with the axis in the natural flow of water and possibly with a flow provider, such a tube may provide a suitable environment for breeding fish. With a through flow of water, the fish will line up in the flow with a higher density than in a closed tank, wherein the fish will move in circles.