WO2014184766A1

WO2014184766A1 - Method and apparatus for removing parasites from fish

Info

Publication number: WO2014184766A1
Application number: PCT/IB2014/061463
Authority: WO
Inventors: Kristian Lillerud; Erling WAAGSBØ
Original assignee: Kristian Lillerud; Waagsbø Erling
Priority date: 2013-05-15
Filing date: 2014-05-15
Publication date: 2014-11-20
Also published as: NO20130687A1; NO340713B1

Abstract

A cleaning system for removing multicellular ectoparasites from fish is described, where a cleaning water flow is directed towards the surface of the fish. Gas bubbles are produced and distributed in the cleaning water flow so that a mixture is formed between the gas bubbles and at least some parts of the water in the cleaning water flow. The mixture is directed towards the surface of the fish and dislodges the multicellular ectoparasites from the surface of the fish on establishment of contact between the mixture and the multicellular ectoparasites located on the surface of the fish. Additionally, a use of a mixture that results when gas bubbles are produced and distributed in at least some parts of the water in a cleaning water flow, and to a method for removing multicellular ectoparasites from the surface of fish are also described.

Description

METHOD AND APPARATUS FOR REMOVING PARASITES FROM FISH

The present invention relates to a cleaning system and method for removing multicellular ectoparasites from the surface of fish. The invention also relates to the use of a mixture that results when gas bubbles are produced and distributed in at least some parts of the water in a cleaning water flow that is directed towards the surface of the fish for dislodging the multicellular ectoparasites therefrom. The multicellular ectoparasites referred to here relate to all types of parasites and creatures that attach themselves to the outside of fish, as, for example, lice (sea lice), parasites, leeches and insects.

Background

Damage caused by, for example, sea lice costs fish farmers huge sums of money each year. There are major challenges associated with the control of sea lice and other parasites on fish, and it has long been known to use different chemical agents to combat lice and parasites. The use of chemical agents, such as vaccination or feed additives, has a number of adverse side effects, and in the aquaculture industry there has been a need to provide alternative methods for combating sea lice and parasites. As an alternative to chemical agents, attempts have been made to use wrasse that feed on the parasites. This is actually a satisfactory solution for cleaning the individual fish, but cannot be implemented with satisfactory capacity on a large scale in a commercial farm. NO304171 describes a device for removing parasites without necessitating the use of chemicals. NO304171 shows a flushing apparatus for removing sea lice from the outside of fish. The fish are led by a water flow through a cleaning pipe. The cleaning pipe is provided with nozzles that are connected to a water pump for cleaning the outside of the fish by utilising the force of the water jet against the skin of the fish. The nozzles are directed towards the outside of the fish such that an effective yet gentle cleaning of the surface of the fish is achieved inasmuch as the force of the water jet against the fish's skin is greater than the force with which the sea lice grip onto the skin. The water jet thus provides a mechanical dislodging effect in that it is directed in towards the skin of the fish.

Furthermore, NO301440 describes a pump device of the ejector type that is suitable for transport of live fish. The pump device is arranged for transport of a main fluid by supplying a primary fluid through a circumferential nozzle arranged in an ejector area. The primary fluid may be either water or gas. During transport of live fish, the main fluid is water containing the fish, and the primary fluid is preferably water. The device according to NO301440 can further comprise a feed pipe for air or oxygen arranged ahead of and/or after the ejector area. The object is to be able to use the pump simultaneously to supply air/oxygen to the water to meet the fish's need for oxygen. According to the patent, the air will be supplied in an area where the fluid velocity of the main flow is low.

OBJECTS

The main object of the invention is to find an efficient, pollution-free and expedient method for removing the multicellular ectoparasites, with a further object of the invention being to increase the performance, capacity and usefulness of the equipment that is known to date, and render it useful on a large scale by increasing its efficiency and capacity.

According to the present invention, an apparatus is provided that provides an improved removal of the multicellular ectoparasites from the surface of fish. This is achieved by the invention as disclosed in the independent claims, embodiments of the invention being disclosed in the dependent claims.

According to the present invention, the cleaning effect is improved in that gas bubbles are produced in a cleaning water flow that is directed towards the surface of fish in order to remove the multicellular ectoparasites (external parasites). The production and distribution of gas bubbles in the cleaning water flow results in a mixture being obtained between the gas bubbles and at least some parts of the water in the cleaning water flow. This mixture is directed towards the surface of the fish and can be brought into the proximity of or in contact with the multicellular ectoparasites, i.e., the lice and any other parasites on the surface of the fish.

This then results in the gentle dislodging of the multicellular ectoparasites from the fish's skin. Tests have shown that a substantial improvement effect is obtained by adding gas bubbles to a cleaning water flow as will be exemplified further below. For a cleaning system to be useful in a fish farm, the cleaning system must have high capacity in terms of volume of fish treated per unit of time.

The invention can be used in vessels, tanks and pipes that are used to transport fish from one location to another, or together with other equipment where it is desirable to cleanse the surface of the fish of the multicellular ectoparasites.

The invention is particularly suitable for use together with a transport system that is employed to move fish from one location to another. An improved cleaning system to remove the multicellular ectoparasites from the surface of the fish will result in a qualitatively improved cleaning process and a quantity increase in the form of an increase in the amount of fish passed through the .transport system per unit of time compared with known equipment. Examination of the fish has revealed that with the cleaning system according to the invention, the sea lice are removed more effectively from the surface of the fish compared with known systems of a similar kind, which have an efficiency where approximately 60% of the sea lice are removed from the surface of the fish. The cleaning system according to the invention has been tried out through repeated testing, and it was demonstrated that the invention gives about 15% more delousing compared with known systems of a similar kind, without this appearing to affect the health of the fish.

It should be mentioned that the transport system could be used for transfer of fish between different locations such as a vessel on shore or on board a boat. The transport system can be designed such that fish can be moved between different levels.

According to the invention, a cleaning water flow in the form of a flushing jet is used that is directed against the surface of the fish, the flushing effect against the fish varying with the fish's radial distance to the nozzle and the angle of the flushing jet relative to the surface of the fish.

Tests have shown that the work process is made more efficient and is stabilised by the addition of gas in bubble form in that the gas bubbles are mixed with the water in the cleaning water flow with which the fish are flushed, and which, for that matter, may also be a part of the transport medium for the fish.

In tests it has been found that the presence of gas bubbles in the cleaning water that is directed towards the surface of the fish has a favourable effect in the removal of the multicellular ectoparasites that have a carapace. One of the reasons for this favourable effect may be that the admixture of gas bubbles in the cleaning water causes the pressure on the carapace of the multicellular ectoparasites to provide a suction cup effect of the carapace against surface of the fish. In particular with regard to the group of ectoparasitic crustaceans to which sea lice belong, this effect is easy to see. The pressure between the inside of the carapace and the surface of the fish corresponds to the water and pressure conditions when the fish are in a net. The fish, together with water, are pushed into the transport system because of the lower pressure that is there. When the pressure in the water surrounding the fish is reduced, a pressure difference is obtained between the ambient pressure and the pressure that is confined between the inside of the carapace and the skin of the fish. The difference in pressure gives a net force with direction which helps the sea lice to become dislodged from the surface of the fish.

This net force increases substantially when gas is added to the water. On the admixture of gas, for example, air or oxygen, to the water, the specific gravity of the mixture is reduced. The gas will acceleratingly expand as the mixture is lifted to a higher level. Gas that is dissolved in the water at atmospheric pressure will effervesce and require more space under the carapace when the surrounding pressure falls.

As experience with the addition of gas bubbles to the cleaning water is in an early stage, it is not possible at this time to conclude definitely that the pressure drop around the carapace causes the dislodging of the ectoparasites. It may be a possible explanation, but it does not have to be the only explanation. What is certain is that an improved effect is obtained in cleaning the surface of the fish when gas bubbles are added, for example, in the form of oxygen, to the cleaning water.

The cleaning system according to the invention comprises a cleaning water flow containing gas bubbles in a mixture with at least some parts of the water in the cleaning water flow. The cleaning water flow containing the mixture can be directed towards the surface of the fish through a cleaning device that is incorporated in a transport system for fish, in an ejector device incorporated in the fish transport system, or in another suitable way which allows the cleaning water flow to have an effective setting angle towards the surface of the fish.

In the case where the invention is incorporated in the transport system, a number of other functions are performed in addition. The transport system carries the fish in water together with fish feed and other substances necessary in connection with the farming of fish. The fish are weighed and counted at a suitable point in the transport system. The transport system has equipment for collecting the multicellular ectoparasites that are removed from the surface of the fish. In the transport system, the fish can be sorted according to size and this sorting can take place under water.

In an embodiment, the transport system is arranged such that it has a siphon-like design, but according to this embodiment the transport system does not use gravity as a driving force as is the case in siphon systems. The transport system comprises, according to this embodiment, a number of pipes that are assembled so as to form a transport pipe with an inlet end and an outlet end, where the water flow carries the fish through a main duct formed in the transport pipe. The inlet end and the outlet end are in water with the surface at the same level, and the pressure conditions are thus identical at both ends of the pipe. There is therefore no force of pressure to push the gas or water through the transport pipe. Such a force of pressure can be provided using a pump. But as it is live fish that are to be transported through the transport pipe by the water flow, the driving force cannot be provided using an ordinary pump where moving parts advance the mass to be transported, because this may harm the fish. A possible way of achieving gentle handling of the fish to be transported whilst a necessary force of pressure is provided to move the water flow with the fish through the pipe arrangement is to use an ejector device that is connected to the pipe arrangement. The ejector device can be designed in different ways, but will in an embodiment comprise a pipe for carrying the fish in the water flow. In the ejector device there is arranged a nozzle construction that has a throughgoing main duct through which the water flow containing the fish is to be passed. The nozzle construction may be positioned inside the ejector device such that there is at least one ejector nozzle between the inlet end and the outlet end. This may be a continuous ejector nozzle that runs around the main duct and which may be annular, or may be provided in that a plurality of slot openings are arranged side by side. Alternatively, the ejector nozzle(s) can be formed in the nozzle construction itself and be positioned radially outside the main duct of the nozzle construction. The nozzle construction does not project from the wall of the ejector device and will thus not be an obstacle to the transport in the main duct. or have any harmful effect on the fish being transported. The nozzle construction will preferably be configured to match the circumference of the main duct through the ejector device. The ejector device is configured such that an injection water flow can be passed in through the ejector nozzle and into a main water flow that is passed through the main duct. A water pump for introduction of an injection water flow into the ejector device can be connected to a feed pipe that is configured in the ejector device. The injection water flow is delivered at a pressure through the ejector nozzle that is higher than atmospheric pressure and is focused towards the surface of the fish to remove the multicellular ectoparasites therefrom.

To transport the water and the fish and any other substance in the transport system, the ejector works in the following way:

The injection water is forced through the ejector nozzle and into the main flow that is transported through the main duct through the ejector device. When there is no water in the main duct and the injection flow is turned on, the injection from the ejector nozzle will have the appearance of a funnel or hollow cone in the main duct. And when the injection flow encounters the medium in the main duct, which at the start is air, later water, and which becomes the main flow, the injection flow works as a force, whose physical source consists of a hollow cone of accelerated water that carries with it and pushes the main flow at an angle towards the centre of the main duct where also the apex of the cone will essentially be located, and which, if other directions of force had not come into play, would have given the main water flow a conical shape. The water cone from the ejector nozzle has an internal funnel form. The external conical form or the internal funnel form is formed by water which flows at great speed from the ejector nozzle towards the centre of the main duct.

The conical funnel, consisting of accelerated water, has a pressure-increasing effect on its outside, whilst on the inside it has a pressure-reducing effect. This effect arises owing to friction between the accelerated liquid and the medium in which it moves. Before the start of the main transport, this medium is basically air. The water flow in the funnel form carries with it air particles that are moved to the outside of the conical form. This reduces the pressure on the inside of the funnel form and lowers the pressure throughout the part of the main duct which runs from and is on the same side of the ejector device as the mass that is to be moved. This means that the relative atmospheric pressure becomes greater than the pressure in the main duct, and the atmospheric pressure presses the water up through the main duct. The main duct will gradually be filled with water. And as the part of the transport pipe which comes after the ejector device is also filled with water, the weight of the vertical water column, from the outlet end to the highest point of the main duct, weakens the counterforce from the atmospheric pressure that the water flow from the ejector nozzle meets at the beginning. The counterforce is smallest when the main duct is filled with water on both sides of the ejector nozzle. The nozzle construction of the ejector device must be adapted to the fish size so that the fish can pass freely through the main duct of the nozzle construction. The fish are transported in the main duct and through the funnel/conical form that is formed when the injection water flow is forced through the ejector nozzle and into the main duct as described above. The velocity of the water in the funnel-shaped water jet is much greater than the speed of the water and fish that are to pass through it. A flushing effect is therefore obtained as the fish pass the ejector nozzle and the injection water flow functions as a cleaning water flow when it strikes the surface of the fish at high speed. The addition of gas bubbles to this injection water flow results in a mixture that has been found to have a favourable effect on the removal of the multicellular ectoparasites, such that they are more easily dislodged by the water flow from the ejector nozzle of the ejector device.

Since the pressure falls with increasing height in the main duct, because the vertical water column becomes shorter, the gas bubbles in the water column expand. The pressure in the gas bubbles is determined by the pressure from the vertical water column between the top point of the main duct and the vertical level at which the gas bubbles are located. The gas bubbles will grow as the pressure in the liquid drops. The specific gravity of the water/gas mixture in the main duct becomes smaller as it goes up to the top point of the transport pipe, such that the velocity of the water flow increases if the energy input from the ejector device is constant. Where the gas is supplied to the ejector device, and the ejector device is located at the highest point of the transport pipe, the specific gravity/pressure ratio as described above will be reversed. The specific gravity and the pressure of the water/gas mixture will increase in the direction of the outlet of the main duct. The fish that enter into the transport pipe are passed by the main water flow

(backwards if it is a salmon) and further into the transport pipe and through the ejector device's funnel-formed or conical injection water flow at a water velocity which at the outset is much greater than the water velocity in the main water flow that carries the fish up to and into the ejector device. The fish are flushed by the cleaning water flow/injection water flow that is directed towards the fish in the main water flow in the main duct. When the cleaning water flow has gas bubbles added, the flushing is found to be more effective for removing the multicellular ectoparasites from the skin of the fish.

The measurement reports from recent tests show that the cleaning effect here is almost 100% removal of the ectoparasites. It should be pointed out here that the known equipment has a delousing effect of 60%. Previously known equipment in which a cleaning water flow is used that is directed towards the surface of the fish for removal of the multicellular ectoparasites has the drawback that it has an uneven and unsatisfactory cleaning effect. The uneven cleaning effect is due to the fact that the diameter of the main duct does not always optimally match the fish size, and thus the distance between the ejector nozzle and the flushing object is too great and therefore the cleaning water flow has

insufficient velocity to flush away the parasites. The water velocity in the cleaning water flow/injection flow is estimated to decrease in inverse potential proportion to the distance from the ejector nozzle, because water from the main flow is mixed into the cleaning water flow. This water is accelerated at the expense of the velocity of the cleaning water flow. When the ejector device is configured with a nozzle construction as described above, the water jet will look like the wall of a funnel. The wall of this "funnel" will be thinnest, have highest velocity and be most effective closest to the ejector nozzle. As the cleaning water flow is focused out in the main duct, and water from the main flow in the transport duct is mixed into the cleaning water flow and accelerated at the expense of the velocity of the cleaning water flow, the effect of the cleaning water flow on the fish will drop sharply. This means that the cleaning effect will vary in relation to the main duct diameter and thus also the diameter of the nozzle construction. These factors must therefore be adapted to the size of the fish in order to obtain a result that is sufficiently good to be used in parasite removal in the fish farming industry.

When gas bubbles are mixed into the cleaning water that is directed towards the surface of the fish, this results in a pressure drop around the multicellular ectoparasites on the surface of the fish so that they dislodge more easily than if only a cleaning water jet had been used without added gas bubbles. By utilising this effect, the cleaning effect will be less sensitive to the distance and angular setting of the ejector nozzle, and the radial distance between the ejector nozzle and the fish will have less impact on the cleaning effect.

Gases that were dissolved in the liquid when it was in the net will be able to be released when the pressure becomes lower.

As a result of the conical/funnel form being formed inside the ejector device as described above, this form carries with it gas or water particles from the medium surrounding it. The particles are given a direction towards the apex of the conical form. The water flow from ejector nozzle that surrounds the base circle of the cone thus is, at the outset, on course for the apex of the cone. But as the conical water flow also carries with it particles that are on the outside of the conical form, a local negative pressure arises from the top of the cone and down towards the ejector nozzle at the base circle of the cone. The estimated pressure fall will initiate a particle flow that goes in the opposite direction to the particle flow that is held in motion at the outer surface of the conical form. This causes a so-called

eddy/whirlpool between the cone and the wall of the main duct where first the air particles, and later the water particles, will rotate with, transverse to and with the main flow in the radial plane between the "cone" and the wall of the main duct, such that the rotational flow follows the outer surface of the conical form towards the centre of the main duct and moves towards the wall of the main duct and back towards the ejector nozzle. This has, depending on the size of the fish, an adverse effect on the fish, which if no preventive steps are taken, can be drawn along by the turbulence and trapped because of the negative pressure between the conical form and the wall of the main duct. The fish might also end up lying sideways in this space.

In addition to the fish being cleaned by the injection flow when the fish are passed through the ejector device, the transport pipe may also be provided with a cleaning device. The cleaning device may be provided with at least one nozzle and a throughgoing main duct that carries the main water flow with the fish through the cleaning device. The cleaning water flow is passed through the nozzle and into the main water flow, the gas bubbles being produced and distributed in the cleaning water flow, and the mixture that is produced between the gas bubbles and at least some parts of the water in the cleaning water flow being focused towards the surface of the fish in the main water flow for dislodging the multicellular ectoparasites from the surface of the fish.

As mentioned above, one or more pumps can drive the cleaning water flow in the cleaning device and the cleaning water flow/injection water flow in the ejector device. In an embodiment, cavitation in the pump can be used to produce and distribute gas bubbles in the cleaning water flow. The gas bubbles can be produced and distributed in the cleaning water flow in the pump, on the discharge side or on the suction side of the pump. The gas bubbles can also be produced and distributed in the cleaning water flow by gas being passed through a separate ejector.

Alternatively, the gas bubbles can be produced and distributed in the cleaning water flow in that dissolved gases or gases are released when the pressure in the cleaning water flow decreases. The gas bubbles can also be produced and distributed in the cleaning water flow as substances that are added

to the cleaning water flow in solid form, such as powder, or in liquid form, and which are dissolved such that gases are released which form bubbles. Medicaments can be added to the cleaning water flow as gas bubbles.

It is further an object of the invention to provide a solution to prevent the fish from being oriented crosswise as outlined above. The problem is solved by inserting a screen in the main duct. The screen, which may be tubular, has little impact on the water flow, but catches the fish that exit the top of the conical form. The tubular screen guides the fish past the eddy in order to prevent them from being caught up in the eddy and getting stuck there.

It is further also a problem when using the invention that the water velocity necessary to carry the fish with the water flow into the transport pipe can be so high that a satisfactory cleaning effect is not obtained as the fish pass through the cleaning device. To solve this problem, it is proposed that slotted gratings be placed in the periphery of the transport pipe just before the nozzle in the cleaning device to reduce the water velocity before water and fish are passed into the area where the water cleaning flow is focused towards the surface of the fish. The slotted gratings can be configured with openings that are connected to a pipe, which in turn may be connected to a water intake pipe, for example, connected to the pressure pump that supplies the ejector device with water. The amount of water that is taken out through the slotted gratings is regulated by valves, thereby controlling both the cleaning effect in that the velocity through the cleaning flow is adjustable in relation to the effect of the removal of the multicellular ectoparasites, and that the volume of fish that is moved through the transport pipe can also be regulated.

The multicellular ectoparasites that are flushed off the fish must be collected otherwise they will attach themselves to other fish. After the multicellular ectoparasites have been dislodged from the fish, they are carried onwards in the water flow through the transport pipe together with the fish. At the outlet end of the transport pipe there is formed an outlet chamber which has a larger cross-section than the transport pipe itself. The water flow containing the fish reaches the outlet chamber and the fish are guided out through a side opening, whilst the multicellular ectoparasites accompanying the water flow are collected in a collecting bag that is arranged around the opening at the end of the outlet chamber in the direction of the water flow. The collecting bag can be made of a filter material and can be removed and cleaned.

The transport pipe and the outlet chamber are tilted with the collecting bag and side opening submerged in water. A pressure drop occurs in the water flow containing the fish and the multicellular ectoparasites, when the water flow is passed over into the outlet chamber, the reason for this being that the outlet chamber has a cross- section that is larger than the cross-section of the transport pipe. The water flow containing the multicellular ectoparasites and the fish meet the water that fills the side opening. Because the water flow has a certain velocity, and a pressure drop occurs in the water flow when it reaches the outlet chamber with the enlarged cross- section, the water in the side opening is accelerated in the same direction as the direction of travel of the main flow and water flows in through this side opening. In the outlet chamber, a screen is secured oriented at an angle across the direction of travel of the main water flow, so that the elements that are too large to pass through the screen are led out in counterflow through the side opening. The water flow containing the multicellular ectoparasites continues through the screen and the multicellular ectoparasites will be collected inside the collecting filter, whilst the water flow continues straight through the collecting filter.

It is also possible to install screens in the outlet chamber in order to sort the fish according to size.

An example of an embodiment of the invention will now be described below with reference to the figures, wherein:

Figure 1 shows an example of an assembly of the cleaning system components; Figure 2 shows an intake part of the cleaning system as shown in Figure 1.

Figure 3 shows a cleaning device that is included in the cleaning system shown in Figure 1.

Figure 4 shows an ejector device as included in the cleaning system shown in Figure 1.

Figure 5 shows a discharge section of the cleaning system as shown in Figure 1. Figure 1 shows an example of an embodiment of the cleaning system according to the invention where a transport pipe 20 is used to transport fish from one location to another. The transport pipe has an inlet end that is configured as two suction funnels 15, see Figure 1 and Figure 2. These suction funnels 15 are connected to suction hoses 2, for example, rubber hoses that carry the fish to a distribution gate 16 before the two suction hoses are brought together in a single tubular duct 21. The fish are shown transported tail first in the direction of flow because the fish shown illustrated here are salmon. Salmon swim against the current in a flow of water, or, put in another way, the salmon turn tail first in the direction of the current.

The fish are then passed to a cleaning device 1 that is configured with a main duct 23 for transport of the fish in a main water flow A through the cleaning device 1. See Figs. 1 and 3. A cleaning water flow in which gas bubbles are produced and distributed in the cleaning water flow B in a mixture between the gas bubbles and the water is passed through at least one nozzle 22 and focused towards the surface of the fish for dislodging the multicellular ectoparasites from the surface of the fish. Because it is desirable to transport a large amount of fish through the transport pipe, it is a goal to have as high a velocity as possible for the main water flow A.

However, it is necessary that the fish should have lower velocity through the main duct 23 in the cleaning device 1 , to allow the cleaning water flow to have time to dislodge the multicellular ectoparasites from the surface of the fish. To ensure sufficiently low velocity through the cleaning device 1, slots 24 are formed in an embodiment of the invention to lead a part of the main water flow A out of the main duct 23. The portion of the water that is drawn out through the slots 24 is passed to a pump (not shown) through an outflow pipe 25. A valve device 30 is used to regulate the discharge through the outflow pipe 25. This can be the same pump that is also used to supply the ejector device with water, or it can be an additional pump that draws the water out before the cleaning process as described above. This is merely an example of how the speed through the cleaning device 1 can be reduced, and other ways of accomplishing this are conceivable, the main point being to obtain high speed up to the cleaning device and a reduced speed through the cleaning zone of the cleaning device.

The fish are transported from the cleaning device 1 onwards through the transport pipe to a counting box 5 that counts the fish and weighs them. From there the fish are transported to an ejector device 6. The ejector device 6 provides a driving force to carry the main water flow through the transport pipe, but also has in addition a cleaning function for fish that are transported in the main flow. Figure 4 shows the ejector device 6 in more detail. A nozzle construction 25 is placed inside the ejector device 61. In the area between the nozzle construction 25 and the ejector device 6 there is at least one ejector nozzle 28. The main flow containing fish is transported through a main duct 27 in the nozzle construction. The ejector device is configured with a feed pipe 29 where an injection water flow is supplied from a pump that may well be the same pump that is connected to the cleaning device 1. The injector water flow is passed into the main water flow through the ejector nozzle 28 and is directed towards the surface of the fish. The injector water flow then functions in this connection as a cleaning water flow against the surface of the fish, the gas bubbles being produced and distributed in the cleaning water flow and the mixture that is produced between the gas bubbles and at least some parts of the water in the cleaning water flow being focused towards the surface of the fish in the main water flow for dislodging the multicellular ectoparasites from the surface of the fish.

As mentioned above, one or more pumps can drive the cleaning water flow in the cleaning device 1 and the injection water flow in the ejector device 6.

From the injector, the fish are passed onwards in the main water flow in the transport pipe and through the discharge pipe 9 and into the outlet chamber 10 where the fish are passed out through a side opening 30, whilst the multicellular ectoparasites that follow the water flow are collected in a collecting bag 31 that is arranged at an end outlet 32 in the direction of flow of the water flow. The collecting bag 31 can be made of a filter material and can be removed and cleaned.

Claims

PATENT CLAIMS

1. A cleaning system for removing multicellular ectoparasites, from fish, where a cleaning water flow is directed towards the surface of the fish, characterised in that gas bubbles are produced and distributed in the cleaning water flow so that a mixture is formed between the gas bubbles and at least some parts of the water in the cleaning water flow, the mixture being directed towards the surface of the fish, and that the mixture dislodges the multicellular ectoparasites from the fish surface on establishment of contact between the mixture and the multicellular ectoparasites located on the surface of the fish.

2. The cleaning system according to claim 1,

characterised in that the cleaning system further comprises a transport pipe in which the fish are transported in a main water flow.

3. The cleaning system according to claim 2,

characterised in that the cleaning system further comprises -a cleaning device connected to the transport pipe, the cleaning device being provided with at least one nozzle and a throughgoing main duct that passes the main water flow containing the fish through the cleaning device, where the cleaning water flow is passed through the nozzle and into the main water flow, the gas bubbles being produced and distributed in the cleaning water flow and the mixture produced between the gas bubbles and at least some parts of the water in the cleaning water flow being focused on the surface of the fish in the main water flow for dislodging the multicellular ectoparasites from the surface of the fish.

4. The cleaning system according to claim 3,

characterised in that the main duct in the cleaning device is configured with slots, water being led away from the main water flow through the slots in order thereby to lower the velocity of the water through the cleaning device.

5. The cleaning system according to one of the preceding claims,

characterised in that the cleaning system further comprises

-an ejector device connected to the transport pipe, the ejector device being configured with a nozzle construction having a throughgoing main duct that passes the main water flow containing the fish through the nozzle construction, the nozzle construction being arranged such that at least one nozzle is provided and where the cleaning water flow in the form of an injection water flow is passed through the nozzle and into the main water flow, the gas bubbles being produced and distributed in the cleaning water flow and the mixture produced between the gas bubbles and at least some parts of the water in the cleaning water flow being focused towards the surface of the fish in the main water flow for dislodging the multicellular ectoparasites from the surface of the fish.

The cleaning system according to one of the preceding claims, characterised in thata pump drives the cleaning water flow.

The cleaning system according to claim 6,

characterised in that production and distribution of gas bubbles in the cleaning water flow is caused by cavitation in the pump.

The cleaning system according to claim 6,

characterised in that the gas bubbles are produced and distributed in the cleaning water flow in the pump, on the discharge side or the suction side of the pump.

The cleaning system according to one of the preceding claims, characterised in that gas bubbles are produced and distributed in the cleaning water flow in that gas is passed through an ejector.

10. The cleaning system according to one of the preceding claims,

characterised in that the gas bubbles are produced in the cleaning water flow in that dissolved gases or gases are released when the pressure in the cleaning water flow decreases.

11. The cleaning system according to one of the preceding claims,

characterised in that the gas bubbles are produced in the cleaning water flow in that substances that are added to the cleaning water flow in solid form, as a powder, or in liquid form are dissolved and gases are released which form bubbles.

12 The cleaning system according to one of the preceding claims,

characterised in that medicaments are added to the cleaning water flow as gas bubbles.

13 The cleaning system according to one of the preceding claims,

characterised in that the cleaning system comprises a collecting unit for collecting the multicellular ectoparasites.

14. Use of a mixture that is formed in that gas bubbles are produced and distributed in at least some parts of the water in a cleaning water flow that is directed towards the surface of the fish for dislodging the multicellular ectoparasites from the surface of the fish.

15. A method for removing multicellular ectoparasites, from the surface of fish,

-producing and distributing gas bubbles in at least some parts of a cleaning water flow, so that a mixture is formed between the gas bubbles and at least some parts of the water in the cleaning water flow;

-directing the cleaning water flow containing the gas bubbles towards the surface of the fish, so that the mixture is brought into contact with the multicellular ectoparasites and dislodges the multicellular ectoparasites from the surface of the fish.