Field of the invention

The present invention relates to a fish farm installation and a method for feeding fish, wherein the fish farm installation comprises a net cage set up to be filled with water and farmed fish, and also a water feeder apparatus for supplying fish feed to the net cage.

Background of the invention

In the aquaculture industry today, the industry is experiencing an increased feed factor. This is despite the fact that the genetics and the salmon feed are claimed to be better than before and that the potential for a low feed factor ought to be present. There can be several factors causing the industry to struggle to realise this potential, but one of the reasons can be a lack of control over whether the fish eat all the feed that is allocated. Today, the feeding is usually done by spreading the feed on the surface of the net cage or in the body of the net cage, down to a depth of about 8 meters. To avoid feed waste, the salmon must then eat all the feed before it sinks out of the net bottom. Feed allocation is controlled and steered by humans, most often from a remote location, using various support systems, such as custom software and an underwater camera. The feed is usually transported out to the net cages from a feed barge through hoses that lie in the sea. The transport of the feed in the hoses is achieved through the use of compressed air or water flow.

Description of prior art

NO20181564 A1 describes a method and a device for mixing feed pellets and water. The device comprises an inlet chamber for feed, a mixing chamber having a water inlet set up downstream of the inlet chamber and an outlet set up downstream of the mixing chamber which can be connected to a main pipe for further transport. The water inlet is arranged to direct the water along an inner wall of the mixing chamber. The document states that intake of water in the feed pipe is in two water streams, as well as a gas inlet for pressurised gas to form a water flow out of the mixing chamber so that the feed and water mixture is transported out.

CN108308080 A describes a system for mixing water and feed before it is distributed to the fish farm net cages. The system includes a water inlet, a feed inlet, a mixing chamber, a pump and an outlet. Feed is mixed into the water stream in the mixing chamber and is pumped further to the fish farm net cage. The feed mixture is introduced into the net cage below the water surface and the feed floats upwards towards the water surface. Objects of the present invention

The invention relates to the feeding of fish in fish farm installations, where the fish feed is added to a stream of water in hoses which are led into a net cage. The fish feed can have positive buoyancy or, as a result of upward directed water flow, is influenced so that it flows slowly upwards instead of sinking. Excess feed will thus rise up to the upper water layer, where it can be collected using a skimmer before it is pumped back to a greater depth inside the net cage and fed out again. In this way, the fish feed could be recycled.

In a system with water as a propellant, the feeding hoses from the feeding barges and out to the net cage should preferably be free of air bubbles. This is because such bubbles can cause varying pressure conditions in the hose and cause the hose to move in the water. Both are unfortunate. The fish feed should therefore be added to the drift water without air being added. This is a challenge for all types of feed.

Conventional fish farm installations using air-based feeding systems have a high energy consumption, which results in higher operating costs. Large effects also lead to higher investment costs both for equipment and for the power systems on board the feeding rafts.

Air as a propellant also makes it practically impossible to supply the fish feed under water. This is due to the fact that the air systems must then be dimensioned with an extra delivery pressure corresponding to the water pressure where the hose ends up. In addition, air supplied with the fish feed will probably disturb the "food dish" for the fish and result in poorer uptake of the feed.

With air as the propellant, the transport speed must be high to prevent fish feed from remaining in the hose. The high speed causes mechanical wear on the fish feed, often referred to as crushing. The proportion of crushes can be significant and the feed dust that occurs is not eaten by the fish, which results in an increased feed factor.

The feeding system as proposed according to the invention solves the above- mentioned problems in that the fish feed is supplied to the drift water through a secondary water flow where all air is removed. This is achieved by establishing a whirlpool where the fish feed is added to the water. This whirlpool sucks down the fish feed at the same time as the water and in this way "pushes" away any air bubbles. The strength of the whirlpool depends on the suction geometry and the amount of water supplied. The strength of the whirlpool should be sufficiently strong to pull down the fish feed at the same time as it must not be too strong as it will cause air to be pulled down.

According to the invention, the use of gas/air as a propellant is avoided, only water is used. By switching from air to water as a propellant, energy consumption is considerably reduced. This is due to the fact that when using water, the transport speed can be reduced considerably. This reduces the loss from friction. In addition, water is incompressible and thus no energy will be stored in the pumped medium that is released/lost at the outlet when the gas expands after leaving the feeding hose.

When using water as a propellant, it is not necessary to increase the pressure on the pumps when the fish feed is added down in the net cage as the density of the propellant is the same as the water in the net cage.

Lower speeds in a water supply system also reduce problems associated with crushing.

Most known water feeding systems are expensive and often complicated. The invention is very simple and will result in low investment and operating costs. Maintenance costs will also normally be lower and uptime higher for simple systems.

Accordingly, with the invention, several advantages can be obtained; less or no feed waste and thus a significantly better feed factor, there will be no discharge which opens up for the use of medicated feed. Because the feeding is better controlled, it should also be possible to achieve increased growth as it becomes easier to optimise the feeding. As mentioned, there is also significantly less energy required when using water in hoses.

Summary of the invention

The above object is achieved with a method for feeding farmed fish in a fish farm installation, the fish farm installation comprises a net cage filled with water and farmed fish, where the method is comprised of:

- feeding fish feed in a water feeder apparatus equipped with a feed pipe, - supply of a first low-pressure water flow in the feed pipe to form a whirlpool which draws in the fish feed and mixes the fish feed with water in the feed pipe, further comprising

- energizing the first low-pressure water stream to provide sufficient pressure for the first water stream including the fish feed to be fed into a second low-pressure water stream in the feed pipe which enters a feeding hose, in that

-the second water stream is being supplied downstream of the first water stream and having a higher flow volume than the first water stream, and intermediate supply of the first water stream and the second water stream being applied to a water pressure which gives a water pressure high enough to bring the first water flow and the fish feed into the second water stream and to be dragged into the feeding hose.

The feeding hose can extend into the net cage, as the fish feed is discharged into a lower area of the net cage and floats up through the water in the net cage.

The fish feed can be dry feed with positive buoyancy.

The fish feed that floats to the surface of the net cage can be sucked up and sent down into the net cage again.

Alternatively, the feeding hose can extend into the net cage, as the fish feed is discharged into the upper area of the net cage and sinks down through the water in the net cage.

Here, the fish feed can be ordinary sinker feed which is sucked up from a conical collector at the bottom of the net cage and which is added to the feed stream again.

The supply of energy can take place through the use of known pump technology such as lobe pumps, centrifugal pumps, screw pumps, ejector pumps or other pumps that are gentle on the feed. Alternatively, the energy supply can take place in that the whirlpool is located at a sufficient height for the necessary pressure to be achieved through the use of gravity (water density x g x h). This will also "ensure" sufficient pressure for the first water stream, including the dry feed, to be fed into the second low-pressure water stream in the feed pipe.

The above object is also achieved with a farming installation for farmed fish, in that the farming installation comprises a net cage set up to be filled with water and farmed fish, as well as a water feeder apparatus supplying fish feed to the net cage. The water feeder apparatus is set up for receiving fish feed and comprises a pump with a feed pipe which, when water is supplied, pulls the fish feed through a feeding hose. The feed pipe of the pump comprises a first water inlet located downstream of a feed hopper for the fish feed, where the first water inlet supplies a first low- pressure water stream forming a whirlpool in the feed pipe which pulls the fish feed down from the hopper and mixes the fish feed with water in the feed pipe. The pump feed pipe comprises a second water inlet located downstream of the first water inlet, where the second water inlet supplies a second low-pressure water stream which has a higher flow volume than the first water flow, and the pump feed pipe comprises a pressurizer, the pressurizer being adapted to apply a water pressure which is high enough to bring the first water stream and fish feed into the second water stream and to be dragged into the feeding hose.

The feeding hose can be connected to equipment for discharging the fish feed in a lower area of the net cage, whereby the fish feed floats up through the water in the net cage.

The feeding hose can alternatively be connected to equipment for discharging the fish feed in an upper area of the net cage, whereby the fish feed sinks through the water in the net cage.

The fish farm installation can further comprise a collector for collecting the fish feed at the surface of the net cage.

The pressurizer of the pump can be located between the first and the second water inlet.

The pressurizer can be a high-pressure water ejector, where the water ejector is connected to a third water inlet located downstream of the first water inlet.

The pressurizer can alternatively be a lobe pump or a centrifugal pump connected in the feed pipe.

The equipment for discharging the fish feed into the net cage can be a perforated hose or ring, said hose or ring is connected to or forms part of the feeding hose. Furthermore, the collector can be connected to a collector pump set up to pump collected fish feed down into the net cage. Here, the collector pump can be connected to a second feeding hose that extends down into the net cage.

In summary, one embodiment of the invention is comprised of discharging fish feed from a feed silo, for example located on a raft or a water feeder apparatus located on a net cage and into a water feeding system using known technology such as a feed screw, belt drive or other technology. The fish feed is then released into a whirlpool where the fish feed is mixed with water so that a mixture consisting of fish feed and water is obtained. The mixture is pressurised by means of a pump which forces the mixture into a larger water flow which then transports the water and the fish feed out to the net cage, where it is then added up or down in the net cage. When the fish feed is released down into the net cage, the fish feed rises to the upper water masses where excess fish feed that has not been eaten by the fish is collected using a skimmer and then pumped down into the net cage to be fed out again. The same can be done for fish feed that is released in the upper part of the net cage. As part of the return of the fish feed, the amount of excess fish feed can be registered, and this registration can be used to optimise the feeding.

Description of figures

Preferred embodiments of the invention will be described in more detail below with reference to the accompanying figures, in which:

Figure 1 shows a principle diagram of an embodiment of a fish farm installation according to the invention, seen from the side.

Figure 2 shows a principle diagram of the fish farm installation shown in figure 1 , seen from above.

Figure 3 shows a first embodiment of a pump which is part of a fish farm installation according to the invention.

Figure 4 shows a second embodiment of a pump which is part of a fish farm installation according to the invention.

Description of preferred embodiments of the invention

The term "net cage" usually means an enclosure in the sea for storage, feeding and care of farmed fish, where the net cage consists of a net bag which is supported by a floating structure. However, the term "net cage" in connection with the present invention must be understood to cover open net cages, closed net cages, and vessels on land (land- based). With open net cages, the fish are separated from the external environment by the net, and the water flows freely through. In closed net cages, a watertight partition is used between the inner environment in the net cage and the water masses outside. Water is pumped in from outside, and feed waste and fish faeces can be collected. In land-based fish farming, the fish is produced in tanks on land, where the water is pumped in from outside.

As can be seen from figures 1 and 2, in one embodiment, the present invention comprises a fish farm installation 10 with a net cage 12 filled with fish 50 which are swimming in a body of water 14. Adjacent to the net cage 12 is a water feeder apparatus 16 which supplies a feeding hose 18 with fish feed which is discharged into the net cage 12. The fish feed can be discharged into the upper or lower part of the water mass of the net cage 12.

The fish feed 48, which can be dry feed with positive buoyancy, can thus be fed into the water feeder apparatus 16 which is equipped with a feed pipe 20, thereafter water can be supplied in the feed pipe 20 which pulls the fish feed 48 to and through the feeding hose 18 which extends into the net cage 12, whereupon the fish feed 48 is discharged into a lower area of the net cage 12 and caused to float up through the water in the net cage. Thereafter, fish feed 48 in a surface 22 of the net cage 12 can be collected. If the fish feed 48 is released into the upper part of the net cage 12, alternatively the fish feed can have a negative buoyancy and be collected in the lower part of the net cage. Here, the fish feed can be ordinary sinker feed which is sucked up from a conical collector at the bottom of the net cage and which is added to the feed stream again.

In the invention, the fish feed is added to a larger stream of water. This is done by an ejector or pump designed to handle water and fish feed in one. The feeding hose 18 is then led to the net cage 12 where it is discharged at the desired depth. In the case of discharges in the lower part of the net cage 12, this depth can, for example, be 20m. Alternatively, the fish feed 48 can be discharged into the upper part of the water mass in the net cage 12. The fish feed to be used can, in an example, be made so that it flows slowly upwards instead of sinking. Alternatively, the fish feed can be made to float utilising current adjustments. The fish will then be able to eat the fish feed while it is on its way up to the surface. If the fish feed is not eaten, it will remain on the surface 22 so that feed waste is avoided. Here, the fish feed can be caught by a circular current in the surface that throws the fish feed out to the sides. Alternatively, a skimmer can be used. The fish feed is then sucked up via a collector pump (not shown) and added to the bottom of the net cage again. The fish will then have the opportunity to eat the fish feed several times.

As shown in figure 1 , the equipment 26 for discharging the fish feed 48 into the net cage 12 can be a perforated hose or ring. The hose or ring can be connected to or form part of the feeding hose 18. Furthermore, a collector 40 as described above can be connected to the collector pump which pumps collected fish feed 48 which flows on the surface 22 down into the net cage 12 again, where the collector pump is connected to a second hose 42 extending into the net cage 12. The lower portion of the second hose 42 can similarly be formed as a perforated hose or ring.

A pellet sensor can be connected to the water feeder apparatus so that sensors can tell whether to increase or decrease feeding. Feeding can then be automated without the need for human monitoring. Furthermore, the amount of collected fish feed can be registered.

Fish feed with positive buoyancy and the method for allocating this will also be very relevant to use in land-based fish farm installations where organic pollution can be a major problem, especially for RAS facilities.

The water feeder apparatus 16 comprises a pump 30 which uses water as a propellant to retrieve fish feed 48 from the water feeder apparatus 16 and transport the fish feed 48 through the feeding hose 18 to the net cage 12. Figures 3 and 4 show a first and a second embodiment of such a pump 30, respectively

Figure 3 shows a feed hopper 52 in the water feeder apparatus 16 which is filled with fish feed 48. Downstream of the feed hopper 52 is a first water inlet 32 which, when water is supplied, draws the fish feed 48 down into an upper part of a feed pipe 20. The first water inlet 32 contributes to the formation of a whirlpool 38 by adding a first, relatively small low-pressure water stream to the side of the feed pipe 20, where the water supply can, for example, have an inlet angle of 30 degrees. The whirlpool stream ensures that the fish feed 48 is sucked down from the feed hopper 52 and that the water in this way "pushes" away air bubbles which can possibly be an obstacle during further transport. The feed pipe 20 is further comprised of a second water inlet 34 which supplies a second low-pressure water stream downstream of the supply of the first water stream through the first water inlet 32. The second water stream has a large water flow, in the sense that the water stream has a larger flow volume than the first water stream. A pump can be used for energy setting and which pressurises the first water flow. Alternatively, static height can be used to pressurise the first water flow. This helps the fish feed 48 to be pushed into the feeding hose 18 and sent on to the net cage 12.

To counteract the back pressure which is created in the feeding hose 18, a pressurizer 24 can be used. As shown in figure 3, the pressurizer can be a small ejector. In this case, the supply pipe 20 of the pump comprises a third water inlet 36 located downstream of the first water inlet 32 and which is connected to the ejector. The ejector will also help to prevent backflow of the fish feed 48 towards the first water inlet 32. The third water inlet 36 and the ejector are located between the first and the second water inlet 32,34. The water inlets 32,34,36 are connected to respective pumps 32a, 34a, 36a for water supply.

Figure 4 correspondingly shows a feed hopper 52 in the water feeder apparatus 16 which is filled with fish feed 48. Downstream of the feed hopper 52 is a first water inlet 32 which, when water is supplied, draws the fish feed 48 down into an upper part of the feed pipe 20. The first water inlet 32 forms a main stream 38 by adding a small low-pressure water stream to the side of the feed pipe 20, where the water supply can have an inlet angle of 30 degrees. The whirlpool stream ensures that the fish feed 48 is sucked down from the feed hopper 52 and that the water in this way "pushes" away air bubbles which can possibly be an obstacle during further transport.

The feed pipe 20 correspondingly comprises a second water inlet 34 which supplies a second low-pressure water stream downstream of the supply for the first water stream. The second water flow has a large water flow, in the sense that the water flow has a larger flow volume than the first water flow. This then contributes to the fish feed 48 being dragged into the feeding hose 18 and sent on to the net cage 12.

To counteract back pressure created in the feeding hose 18, a pressurizer 24 can be used. As shown in figure 4, the pressurizer 24 can be a lobe pump or a centrifugal pump. The pressurizer 24 will form a third water flow, here shown as 36. The pressurizer 24 will naturally also help to prevent backflow of the fish feed 48 towards the first water inlet 32. The pressurizer is located between the first and the second water inlets 32,34. The water inlets 32,34 are connected to respective pumps 32a, 34a for supplying water