NO20221106A1

NO20221106A1 - Arrangement and a method of removing parasites from farmed fish

Info

Publication number: NO20221106A1
Application number: NO20221106A
Authority: NO
Inventors: Edvard Bakke
Original assignee: Br Bakke As
Priority date: 2020-04-01
Filing date: 2020-12-22
Publication date: 2022-10-17
Also published as: WO2021201686A1

Description

ARRANGEMENT AND A METHOD OF REMOVING PARASITES FROM FARMED FISH

Technical Field

[0001 ] The present invention relates to an arrangement and a method of removing parasites from farmed fish. In particular it is directed to mechanical delousing of farmed fish, such as salmon.

Background Art

[0002] Parasites, and in particular salmon lice (Lepeophtheirus salmonis), have been a problem in fish farming for many years. The parasites usually do not kill the fish per se but weaken the fish and makes it susceptible to disease. Fish that have been greatly affected by lice will have an increased deadliness, and if it survives until slaughtered, the damage done by the lice will reduce the quality and value.

[0003] Great efforts have therefore been undertaken to reduce the problem. In the early days of fish farming chemical treatment was the prevailing treatment but found to be environmentally damaging, and in addition the lice showed resistance towards many chemicals. Consequently, many non-chemical methods have been developed, such as warm water treatment, freshwater treatment, ozone or hydrogen peroxide treatment, cleaner fish, laser, UV light, mechanical treatments, such as brushing and water spraying.

[0004] Some of the treatments have been found to work well in particular stages of the lice development, others have been found to easily damage the fish if not used correctly. Mechanical treatments, such as brushing and water spraying, may damage the fish severely if a too great force is used.

[0005] There exist several devices for water treatment, such as by spraying, of the fish, some are combinations of different methods, such as warm water or freshwater treatment in combination with spraying. Examples are shown in:

[0006] US 20180255749, which shows treatment facility, including a water spraying apparatus, through which the fish is fed. The spraying is combined with warm or cold water, pH raising or lowering or osmotic treatment. The fish is fed with its head first through the spraying device. The nozzles are arranged at outer ends of a plurality of arms that are brought into contact with the fish. The nozzles spray a water jet at an angle between 90° and substantially parallel with the surface of the fish in a rearward direction (from head to tail).

[0007] NO 342036, which describes a treatment facility where the fish first is subjected to a half minute bath in lukewarm water and then optionally flushed with water.

[0008] NO 332298, which describes a treatment facility where the fish is brought through a liquid bath formed by a U-shaped pipe. The bath can be lukewarm water.

[0009] WO 2015/143549, which describes a treatment facility in which the fish is sent down a long and winding slide where it is subjected to radial spraying and to warm water.

[0010] NO 344624, which shows a treatment device comprising a net with openings that the fish is forced through. As the fish swims through the openings it is sprayed with low pressure water. Lice is removed from the water by rising air bubbles and a skimmer.

[0011 ] NO 304171 , which shows a treatment apparatus in which fish is brought through a tube having spray nozzles. The nozzles are directed at an angle towards the oncoming fish to spray in a direction from head to tail.

[0012] NO 343268, which shows a treatment facility where fish is pumped through a channel and into a treatment chamber where the fish is flushed and treated with chemicals, warm water or laser. The flushing is done with low pressure jets.

[0013] EP3302047 describes a spraying device having a cylindrical filter member with holes. Spray nozzles are arranged at the inlet and/or outlet ends of the filter member. The spray nozzles are directed towards the middle of the filter member.

Summary of invention

[0014] The present invention has as a primary object to increase the efficiency of the delousing without damaging the fish. This is achieved by...

Brief description of drawings

[0015] The invention will now be described, referring to a preferred embodiment illustrated by the accompanying drawings, in which:

Figure 1 shows a part of a treatment facility for removing parasites from fish, Figure 2 shows a cross-section of a spraying device according to the invention,

Figure 3 shows a detail of the spraying device of figure 2,

Figure 3a shows a similar view as figure 3, but with the converging part added,

Figure 4 shows a nozzle arrangement according to the invention, and

Figure 5 illustrates schematically fish travelling through the spraying device of the invention.

Detailed description of the invention

[0016] Figure 1 illustrates a part of a treatment facility for removing parasites from fish. The facility has a strainer 1 , which is shaped as a substantially flat chute with openings to let water through. The fish is sliding down this strainer and water is separated from the fish. Downstream of the strainer 1 there is a bathtub 2 supplied with a treatment liquid, such as lukewarm water (typically 25-28°C). A paddle wheel 3 gently feeds the fish through the bath 2.

[0017] So far, the treatment facility is known per se.

[0018] Downstream of the bathtub 2 a spraying device 4 according to the invention is arranged. This will be further explained below. Further downstream, the fish is let onto a washing table 5 where water containing lice that have been flushed off the fish and the fish are separated. The fish is then returned to the pen.

[0019] Figure 2 shows the spraying device 4 in cross-section from the side. The device has an inlet 6 for water to be used for spraying and an outlet 7 for spent water. The fish is let through a channel 8 formed by an upstream converging part 8a and a downstream uniform cross section part 8b. Both parts are formed by ribs 11 (see figure 3 and 3a), such as a plurality of round bars, that are arranged with a lateral distance therebetween. The space outside of the channel is connected to the outlet 7 via a drain 9, so that spent spray water can be collected and conducted to a filter to filter out lice therefrom.

[0020] The channel 8 has a ridge 10 (see figure 3), which is formed by arranging some of the ribs 11 , of both the converging part 8a and the uniform cross section part 8b, inwards relative to the remaining ribs. In the converging part 8a, the ribs 11 of the ridge are at the same level as the neighbouring ribs close to the opening and extend upwards to meet the ribs of the uniform cross-section part 8b. Consequently, they form a ramp.

[0021 ] Figure 3a shows the same view as figure 3, but in figure 3a the converging part is also included.

[0022] The ridge 10 divides the channel 8 into two parts. The fish will be directed into the right or left part of the channel by the ridge 10.

[0023] At the uniform cross-section part 8b a plurality of jet nozzles 12 are arranged. The nozzles 12 are set at spaced apart locations and are directed at an angle downstream of the flow of fish.

[0024] Figure 4 shows an assembly comprising two nozzles 12, which are angles slightly towards one another to create an overlapping spray pattern. The nozzles are so-called flat jet nozzles, i.e. the spray 12a created is fan shaped. Thereby each nozzle can cover a large proportion of the circumference of the channel.

[0025] Figure 5 shows a schematic cross-section of the channel 8. This may be the right or the left part of the channel 8. Due to the ridge 10, the fish will be turned with its head downstream. Tests have shown that around 70-80% of the fish will enter the channel 8 with its head first.

[0026] The downstream direction of the nozzles 12, together with the orientation of the fish with its head first ensures not only that the water spray from the nozzles hits the parasites, such as fish lice, from the rear of the parasite, but also that the spray is in the same direction as the intended transport direction of the fish. This ensures both that the lice is lifted off the fish from the and is more easily removed, since the lice is adapted to withstand a current from the front but not from the rear.

[0027] The fish will also be pushed through the channel by the spray and there is substantially less chances for the fish to swim against the stream.

Claims

1. A treatment arrangement for removing parasites, such as fish lice, from farmed fish, said arrangement comprising a spraying device having a channel therethrough;, said channel forming a feeding path for said fish, said channel comprising openings for separating water and parasites from the fish; and a plurality of spray nozzles directing a spray of water into said channel, characterised in that the channel has a ridge extending along said channel, dividing the channel into a right and a left part, causing the fish to be fed through the channel with its head first, and that said plurality of nozzles are directed at an angle in the downstream direction of the feeding direction of the fish.

2. The treatment arrangement of claim 2, characterised in that the channel is set at a 30-degree angle downwards in the feeing direction of the fish.

3. The treatment facility of claim 1 or claim 2, characterised in that the nozzles are arranged at a 130-degree angle relative to the feeding direction of the fish.

4. The treatment arrangement of any of the preceding claims, characterised in that the channel is formed by a plurality of parallel ribs arranged with a mutual distance.

5. The treatment arrangement of any of the preceding claims, characterised in that the spray from the nozzles has a pressure of 3-5 bar.

6. The treatment arrangement of any of the preceding claims, characterised in that the spray has a spread angle of 20-30 degrees.

7. The treatment arrangement of any of the preceding claims, characterised in that the spray nozzles covers 300 degrees of the circumference of the chamber.

8. The treatment arrangement of any of the preceding claims, characterised in that a warm water bath is arranged upstream of the spraying device, for treatment of the fish with water having a temperature of 25-28 °C.

9. The treatment arrangement of claim 8, characterised in that the warm water bath comprises a drum with paddles to carry the fish into and out of the bath.

10. A method of removing parasites from, such as fish lice, from farmed fish, comprising spraying said fish with water, characterised in that said fish is turned with its head forward in the direction of movement and spraying said fish at an angle in the downstream direction of movement of the fish.