From a second aspect, the invention relates to a method for culturing fish wherein the fishes are cultured in a basin having a number of sections where adjacent sections are delimited from other by means of partition walls, and seal- able openings are arranged in the partition walls so that adjacent sections are connectable with each other, fishes of different age groups being present in differ- ent sections and fishes of one age group being transferred from a section to an adjacent section by setting the interjacent opening in open position.

Background of the Invention Since long it is known to culture fish in ponds, basins, aquariums and the like. Although this in general results in a more economic production of fish for food than catching wild fish, plants for fish culturing may in many cases become costly and expensive to operate. One way of attaining an efficient culturing is to culture the fishes in a number of different basins or sections in such a plant, where in each section fishes of one and the same age group are cultured. These are then transferred from one section to another as they grow larger and demand more space, the size of the sections then being increased.

At such plants having a number of culturing sections it may be of great significance for attaining an economically efficient operation how the same sec- tions are arranged in relation to each other and how the fishes are transferred from one section to another.

Examples of attempts at achieving fish culturing plants with the objective of attaining an efficient design in this regard are described in US 3 773 014, US 4 003 337 and US 5 038 715.

Thus, 3 773 014 describes a plant where a number of sections are posi- tioned above each other in a basin tower, where the youngest fishes are cultured

in the uppermost section and fishes of increasing age are cultured in the subjacent sections.

US 4 003 337 describes a plant having concentrically arranged annular sections parted by ring-shaped walls, with a shutter in each partition wall for transferring fishes from one section to another. The sections have a radially out- wards increasing volume for culturing fishes of increasing age.

US 5 038 715 describes a plant having a large number of sections arranged in an intricate network.

Said previously known plants may from certain aspects enable an efficient culturing of fish. However, none of these plants are designed in a way being opti- mal from all aspects especially in respect of the interrelation of the sections and in regard of the communication between these for the transfer of fishes. Furthermore, the known plants do not permit ecological culturing of fish. Thus, there is a need of further enhancements.

Description of the Invention The object of the present invention is to accomplish a solution which meets this need of enhancements and that thus even further endeavour to opti- mise the design of the fish culturing plant by way of an efficient arranging of the sections in relation to each other and an efficient system for the transfer of fishes from one section to another, and to accomplish ecological culturing of fish.

This object has from a first aspect of the invention been attained by a fish culturing plant of the kind specified in the preamble of claim 1 comprising the spe- cial features that the sections are arranged consecutively in a helix-like pattern in a number of turns, that the partition walls comprise a helix-like running wall as well as a number of transverse walls, each transverse wall running between two adja- cent turns of the helix-like running wall that the openings are arranged in the transverse walls that the plant is provided with a foddering appliance comprising a number of foddering positions where at least some of the dispensing spots are arranged so that dispensing of fodder is effected in the vicinity of each transverse wall, that the plant comprises a housing encompassing the basin so that it is secluded from the air and water of the surroundings and that the plant comprises a service tunnel running under the basin in which a pumping station is arranged for the pumping of water in and out of each section individually, the inlet and outlet of

a section being situated at each end of the section, maintenance devices for the adjustment of quality and temperature of the water in each section individually and filtration and purification devices.

Here, helix-like is not to be understood merely as a circular helix, but also a helix which may assume, for instance, an oval, square, rectangular or another polygonal character.

By virtue of the helical shape of the plant with sectioning in the helical direction of consecutive sections, an efficient utilization at a low cost is obtained.

Furthermore, by disposing the openings for transfer of fish from one section to another in the transverse walls, well defined transfer points are obtained posi- tioned in such a way that inlet opening and outlet opening in a section will be at each end of the section, which facilitates keeping each group of fishes apart from those situated nearest. The well-defined sites of the transfer points furthermore facilitate to, by different means, make sure that you simply and safely can transfer a group of fishes from one section to the next. By having the dispensing spots positioned as mentioned the fishes may by means of dispensing from the same be enticed to swim over to the adjacent section. Thereby, a simple and reliable opportunity to transfer a group of fishes from one section to the subsequent is pre- sented. Furthermore, such a transfer is very kind to the fishes.

By virtue of the basin being contained in housing which secludes it from surrounding air and water, it is attained that the fishes will neither be exposed to external biological influence or external polluants nor that the fish culturing plant will contaminate the surroundings. By arranging a service tunnel situated under the basin, the different sections may in a simple way be reached within the system secluded from the surroundings. Furthermore, by the fact that the equipment for the operation of the plant is arranged in said tunnel, a saving of space is attained.

The fact that the pumping station and other managing devices serve each section individually, permits that conditions can be created in each section that are adapted to the age group of fishes that is therein. The filtration and purification devices further contribute to a high hygienic level of the plant. The stated posi- tioning of inlet and outlet for the individual sections ensures a controlled flowing- through of the water, so that a flow formation is formed which emulates natural conditions and which gives an improved mixing of oxygen. Together, these factors

enable an ecological culturing of the fishes on a large scale without influence from the surroundings.

According to a preferred embodiment of the invented plant, the sections have different volume with increasing volume from within and outward, seen in the helical direction.

Thereby, the helical shape is utilized in order to achieve the increasing volume of the section, which fishes of increasing age demand.

According to yet a preferred embodiment, each salable opening is arranged in the lower half of the transverse wall and may be closed by means of a vertically moving shutter.

By arranging the opening in the lower part of the wall, an efficient way to transfer the fishes even at different levels of the liquid surface is enabled. This may be especially advantageous in those cases liquid is pumped out or into some section in connection with the transfer. Furthermore, a vertically moving shutter enables a simple operation at opening and closing of the opening and minimizes the risk of damage to the fishes in connection with the manoeuvring.

The above-mentioned advantageous embodiments of the invented fish culturing plant are defined in the claims depending on claim 1.

The set up object has, from the second aspect of the invention, been attained by a method of the kind defined in the preamble of claim 4 comprising the special measures to arrange the sections consecutively in a helix-like pattern in a number of turns, that the fishes are transferred from one section to an adjacent section by opening an opening in a transverse wall interconnecting two adjacent turns of the helical walls of the sections, the fishes being induced to pass the respective opening by supplying fodder in the vicinity of the opening, that the basin is contained in a housing so that it is secluded from surrounding air and water so that water is pumped out and in individually in each section with a pumping station arranged in a service tunnel situated under the basin, the water being pumped in at one end of a section and out from the other end of the section, that the quality and the temperature of the water is adjusted in each section individually by means of maintenance devices situated in the service tunnel and that the water is filtered and purified.

By this method, advantages are attained of a kind similar to those attained with the invented plant and that have been accounted for above.

Preferred embodiments of the invented method are stated in the claims depending on claim 4. Advantages of a kind are gained with these embodiments that correspond to what is gained with the preferred embodiments of the invented fish culturing plant and that have been accounted for above.

The invention is closer described by the following detailed description of an advantageous embodiment example of the invented fish culturing plant, refer- ence being made to the appended drawing figures.

Brief Description of the Drawings Fig 1 is a view from above of a fish culturing plant according to the invention.

Figs 2-8 are each a longitudinal section through a part of two adjacent sections of a basin of fig 1 and illustrating different steps in the transfer of fishes from one section to an adjacent.

Figs 9-15 are each a view from above of two adjacent sections of a basin of fig 1 and illustrate different steps in the transfer of fishes from one section to an adja- cent.

Fig 16 illustrates partly in perspective view and partly in section a fish culturing plant according to fig 1.

Description of Advantageous Embodiment Example A fish culturing plant according to the invention is illustrated in a view from above in fig 1. The basin of the plant is in the example shown of a substantially square shape with a side of approx. 100 m. A helix-like running wall 9 forms a helix-like running canal in the plant. By a number of transverse walls 11-17 which connect two adjacent turns of the helix-like running wall 9 with each other, the canal is divided into a number of sections 1-8. The distance between two adjacent turns of the helix-like running wall 9 is substantially constant, approx. 5-7,5 m.

Thereby, the different sections will be of an increasing volume, from within and outward. The helix-like running wall 9 has on the upper side thereof a width which is sufficient to form a footway. The depth of the basin is approx. 3 m.

In each transverse wall 11-17, a shutter is arranged which might uncover an opening in order to establish communication between adjacent sections. The openings provided with shutters and the function thereof is described in more detail further down.

Under the basin, a service tunnel 18 extends in which devices requisite for the maintenance of the plant are constructed. These devices comprise, among other things, a pumping station by means of which water may be pumped into and out of each section individually. Furthermore, there are filtration and purification devices. With the arrows A, it is illustrated how clean water is pumped in and with the arrows B it is illustrated how unclean is pumped out. All refuse is filtered and is taken care of so that the surroundings are protected from pollutants. Maintenance devices also comprise devices for adjustment of the quality and the temperature of the water so that it may be adapted individually for each section of the respective age group.

In each section, there is a foddering shutter 19 for feeding of the fishes that are cultured in the plant. This is described in more detail further down.

In the basin, fishes are cultured divided into different age groups. In the innermost section 1, fertilized roe or fry are put out. In the next section 2, fishes of a somewhat older age group are cultured and in yet the next section 3, fishes of a yet older age group are cultured etc. The eldest age group is thus cultured in the outermost section 8, from where the fishes are taken out as edible fish when ready-grown. When fishes have been cultured a certain time in a section and grown so that they are mature to be transferred to the one being situated closest outside, the shutter between these two sections is opened so that transfer may take place.

The total the length of the canal is approx. 1600 m, but thanks to the heli- cal shape thereof, the plant become very compact and may even be located in densely populated areas. The compact design makes it fairly easy to embody the plant in a housing so that it become secluded from the air and water of the sur- roundings. Thereby, the fish is protected from natural and unnatural catastrophes such as diseases, toxins and sabotage.

In fig 2, two adjacent sections, e. g. the sections 3 and 4, are shown in a longitudinal section through the canal. The sections 3,4 are separated by the transverse wall 13, which at the bottom has an opening 23. The opening 23 is in the position shown in fig 2 closed by a shutter 33. The shutter 33 may be dis- placed upwards in the transverse wall 13 so that the opening 23 is uncovered. In the innermost 3 of the two sections, there are fishes of an age group that is mature

to be transferred to the section 4 being situated outside. Conveniently, some time has elapsed since the fishes were last fed so that they will be fairly hungry.

When this is to take place, you first assure yourself that section 4 is evacuated of fishes by the fishes that previously occupied it having been trans- ferred to section 5. Thereupon, water is pumped away from section 4 so that it becomes emptied, whereupon it is conveniently cleaned. By means of cleaning between each batch of fish cultured in a section, the risk of diseases is diminished.

The next step is to pump water from section 3 to section 4 so that the water levels are equalized, which is illustrated in fig 3.

Then the shutter 33 is pushed up in the transverse wall 13 so that the opening 23 is uncovered, which is shown in fig 4. The fishes then are enabled to swim into section 4. In order to entice them to do so, feeding is effected in the proximity of the transverse wall 13 of section 4. This is effected through the mouth 21 of a feeder pipe 20 that is movable, extending from the foddering shutter 19, see fig 1.

Therefore, the hungry fishes swim into section 4, which is illustrated in figs 5 and 6. In order to entice the fishes to swim far into section 4, the mouth of the feeder pipe 20 is moved farther on into section 4.

In fig 7 is illustrated how all fishes have swum into section 4 and the feed- ing is effected in the farthest end of the same. Now the transfer is completed and the shutter 33 is displaced downwards in order to once again shut the opening 23, which is illustrated in fig 8.

Now section 3 may be drained of water and cleaned. Then, section 3 is ready to receive fishes from section 2.

The course described in connection with figs 2-8 is also illustrated in views from above in figs 9-15.

Figs 9 and 10 illustrate the sections 3 and 4 in the position shown in figs 2 and 3, i. e. when all fish is still left in section 3.

In fig 11, the shutter has been drawn up and the fishes are fed through the mouth 21 of the feeder pipe 20 positioned up against the transverse wall 13. In fig 12, some of the fishes have swum into section 4. The mouth 21 of the feeder pipe is moved farther into the section in order to entice the fishes farther into the sec- tion and enable oncoming fishes to enter.

In figs 13 and 14, all fishes have swum into the section 4 and the mouth of the feeder pipe is continuously moved towards the farthest end of the section.

In fig 15, the opening between the sections 3 and 4 has been closed and the position corresponding to the one in fig 8 has been reached.

Fig 16 illustrates some details of the plant. The foddering shutter 19 through which the feeder pipe may be led is hermetical. A ladder 22 is provided in order to enable climbing down in the respective section. The service tunnel 18 is provided with a treatment unit 23 in each section. The treatment unit 23 com- prises, among other things, water filter, oxygen feeder, water cooler and water pump. An impermeable shutter 24 enables the opportunity of via a ladder 25 climbing down from the basin to the service tunnel 18.

In the figure is furthermore illustrated how water being dirty and deficient in oxygen as is shown with arrow B is sucked out from the end of a section, in this case section 7 in order to undergo a treatment comprising, among other things, fil- tration, cooling, oxygenating, sampling etc. Thereupon, the treated water as is shown with arrow A may be pumped into section 8 or back to section 7.

The service tunnel 18 is situated under the basin and secluded therefrom so that machinery, electric installation, telecommunication equipment are pro- tected and so that staff members may stay in the tunnel. The transverse walls with the shutters are all situated directly above the tunnel, which in a simple way enables the manoeuvring of the shutters by means of the machinery or manually.

The helix-like running wall 9 may be a double-wall with a space between the wall layer of approx. 0,5 m, whereby service personnel may move around therein. A number of basins may be constructed on top of each other.

In the present application, the invention is described related to fish. How- ever, in the present application, it will be appreciated that fish includes all types of aquatic animals that may be used as food for people and animals, e. g. shrimps and other shellfish.