GB2550024A

GB2550024A - Arrangement for the treatment of aquaculture fish

Info

Publication number: GB2550024A
Application number: GB1703767.2A
Authority: GB
Inventors: Carlsen Helge
Original assignee: Senta Sea As
Current assignee: Senta Sea As
Priority date: 2016-03-09
Filing date: 2017-03-09
Publication date: 2017-11-08
Also published as: GB201703767D0; NO341934B1; NO20160406A1

Abstract

An arrangement for delousing of caged fish by cooling the processing water (salt or fresh) to below sea temperature in a closed system. The lice get a cold-water shock and let go. The arrangement comprises an inlet 1 for fish to be treated, a first water separator 3 which separates the water from the fish and which is arranged behind the inlet, a processing pipe 4 that the fish passes through, the processing pipe containing processing water for the treatment of the fish, a second water separator 5 arranged at the outlet of the processing pipe and which separates the processing water from the fish, an outlet 11 for treated fish arranged behind the second water separator, a refrigeration unit 9 for cooling the processing water from the second water separator, and a circulation pump 8 which pumps the processing water through the refrigeration unit back to the inlet of the processing pipe. The arrangement may further include first 6, 7 and second filters 13 for filtering the water that passes though the separators, and an oxygen supply unit 14. The processing pipe may be zigzag shaped.

Description

Field of the Invention

The present invention reiates to an arrangement and method for the removai of sea lice on fish in fish farms.

Background

The aquacuiture industry is an important primary industry that empioys many peopie and creates substantiai vaiue in terms of jobs regionaiiy and iocaiiy. This industry is, however, under attack by organisms such as sea iice (Lepeophtheirus saimonis), but aiso by other parasites such as gyro (Gyrodactyius saiaries) and diseases such as AGD. Sea iice are crustaceans that muitipiy on fish and live off mucosa and blood from fish. Sea lice inflict huge economic losses on the aquaculture each year, while at the same time, the lice inflict much pain and suffering on the fish. Sea lice infestation can be fatal to the fish if it is not deloused. Sea lice can attack a fish farm so powerfully that emergency slaughter is the only possible way of bringing the attack under control. Live sea lice can swim relatively quickly and can also jump from one fish to another so that it is absolutely necessary to combat lice effectively, but in a way that is gentle on the fish and the surroundings. A method used today for the treatment of fish for lice involves that the fish is introduced into an enclosed pool where chemicals that kill the lice are introduced. The pool may be formed by drawing a sheet outside a regular fish cage. Otherwise, fixed containers or well boats can be used. The weakness of such a method is that the treatment is a strain on the fish and the chemicals are afterwards pumped out into the nature and burden it. WO 2014/129908 discloses a method for treatment of fish for lice wherein the fish is introduced into a water bath with chemicals added. The chemicals in question are oxygen radicals such as hydrogen peroxide and ozone. At elevated temperatures said radicals will become too active and actually harm the fish. To prevent this, the treatment bath may be cooled.

However, there are treatment methods that avoid the use of chemicals. From Norwegian Patent No. 332298 there is known a method where the fish is treated with lukewarm water (30°C) for a short time period of about 30 sec. The hot water makes the lice release the fish quickly. The fish is led from one cage to another cage through a downwardly bent pipe, like a large water trap, containing heated water. This construction allows treatment of the fish in a continuous process while it is pumped between the cages. The heat treatment is, however, prone to damage the mucus/fat layer on the outside of the fish. Moreover, the treatment stresses the fish. Stress is adverse for farmed fish as it causes a higher mortality. Both the heat and the pumping itself causes stress in the fish.

Fish are also treated for lice by hosing. In this case, the fish is hosed down with strong water jets. The water jets are directed so that they flush against the direction of the scales of the fish. Again, the process stresses the fish.

Summary of the Invention

It is an object of the present invention to provide a method for the delousing offish that is gentler to the fish than known methods, is energy efficient and does not result in pollution of the surroundings.

This is achieved with an arrangement and a method as stated in the appended claims.

Detailed description

The invention will now be described in detail with reference to the accompanying drawing.

The figure is a schematic diagram showing a delousing arrangement according to the invention. The fish to be treated is located in a first cage B.

The invention is based on treating the fish with cooled water. The shock when the fish is introduced into the cooled water causes the lice to release the fish. To increase the effect, the water can additionally be fresh, and optionally a chemical may be added.

The facility includes a suction hose 1 which is connected to a pump 2 to retrieve fish-containing water from Cage B up to a first water separator 3. In the water separator 3, the water is strained off and brought through a return hose 12 to a lice filter 13 before it is led back to the sea. The salmon is brought from the first water separator 3 and into a processing pipe 4 that contains processing water, i.e. the liquid that the fish is to be treated with. The processing pipe is zigzag-shaped with an entry portion located at a first upper level, whereupon the pipe folds back upon itself and leads back at a lower level, whereupon it again turns and folds back at a bottom level. At the outlet of the processing pipe 4 there is a second water separator 5. Here, the processing water and fish are separated, and the fish is returned either to the cage B through return hose 11 or led to another cage C containing only deloused fish, in order to avoid reinfection.

The processing water is led from the second water separator 5 down to lice filters 6 and 7. Behind the lice filter or filters 6, 7, there is arranged a circulation pump 8 which pumps the processing water in a substantially closed circuit around the processing pipe 4. In the closed circuit there is a water tank 9 with an installed refrigeration unit (not shown). The cooling system is arranged to maintain the temperature of the processing water lower than in Cage B, so that the fish experiences a cold shock when it enters the processing pipe. Salmon and trout, for instance, are initially cold-water fish and handle the temperature decrease with ease. Sea lice will not cope with temperature shock easily, and will let go of the fish. They will follow the water flow onward and be captured by the filters 6, 7. The heat from the refrigeration unit could be used for heating elsewhere in the fish farm.

Since the processing of the fish takes place in a virtually closed circuit, the water must be supplied with oxygen from oxygen source 14. The oxygen source is in this case arranged behind the water tank 9, but the order of the filters, circulation pump, water tank/cooler and oxygen supply can be varied as convenient.

The invention can also be practiced in an alternative embodiment, where cold water is supplied from an external source, for example by pumping it up from greater depths in an inlet or by supplying water from a watercourse. The latter means that the water will be fresh, which can have further advantages. The facility will then also function at outbreaks of AGD. The water in the tank 9 should then be fresh in addition to being cooled, so that the effect of the process may be doubled. In such an arrangement, the processing water is discharged to the surrounding sea behind filters 6, 7. Also, it will then generally be unnecessary to supply oxygen.

The water in the processing pipe 4 should be substantially lower than the body temperature of the fish. The temperature difference may be in the range from 5 to 20°C and preferably in the range of 5-10°C and most preferably within 5-7°C. This temperature range is also dependent on the ambient temperature, i.e. the temperature in the cage. For example, at a water temperature of 12°C, it may be appropriate to use a temperature of 5-6°C in the processing pipe 4. At a substantially lower temperature in the cage it may be difficult to carry out delousing. A possible alternative in such a case could be to use two processing plants, where the fish is first treated with slightly heated water where the temperature is raised by a few degrees, before the fish is then treated with cooled water. By using moderately heated water, damage to the fish can be avoided. The two processing plants can be connected in such a way that the heat from the refrigeration unit in the last processing plant is used to heat the water in the first processing plant.

In a simplified arrangement, the delousing treatment involves simply pumping the fish from the cage into a closed compartment containing cold water, such as a tank or a well boat. In particular, well boats have adequate cooling machinery that are able to keep its water tanks at a proper temperature. However, in such a simplified setup, lice may be pumped back into the cage with the fish after treatment, where it may revive and reinfect the fish. For this reason, the fish should be conducted through a water separator when they are removed from the tank.

Claims

Claims

1. An arrangement for the treatment of farmed fish, comprising: an inlet (1) for fish to be treated, a first water separator (3) which separates the water from the fish and which is arranged behind the inlet (1), a processing pipe (4) that the fish passes through, the processing pipe containing processing water for the treatment of the fish, a second water separator (5) arranged at the outlet of the processing pipe (4) and which separates the processing water from the fish, an outlet (11) for treated fish arranged behind the second water separator (5), characterized in a refrigeration unit (9) for cooling the processing water from the second water separator (5), and a circulation pump (8) which pumps the processing water through the refrigeration unit (9) back to the inlet of the processing pipe (4).
2. The arrangement of claim 1, wherein there is provided a first filter (6, 7) for filtering the processing water from the second water separator (5).
3. The arrangement of claim 1 or claim 2, wherein separated water from the first water separator (3) is led to the surrounding sea through a second filter (13).
4. The arrangement of any one of claims 1 to 3, wherein the processing pipe (4) is zigzag-shaped with an initial portion, an intermediate portion folded back below the initial part and an outlet part which is folded back below the intermediate section.
5. The arrangement of any preceding claim, further comprising an oxygen supply unit (14) arranged to supply oxygen to the processing water.

5. An arrangement for the treatment of farmed fish, comprising: an inlet (1) for fish to be treated, a first water separator (3) which separates the water from the fish and which is behind the inlet (1), a processing pipe (4) that the fish is passed through, the processing pipe containing processing water for the treatment of the fish, a second water separator (5) arranged at the outlet of the processing pipe (4) and which separates the processing water from the fish an outlet (11) for treated fish arranged behind the second water separator (5), characterized in a first filter (6, 7) arranged for the filtering of processing water from the second water separator (5), the used processing water being fed to the ambient sea, means for supplying fresh processing water to the inlet of the processing pipe (4), the processing water being cooler than the water at the inlet (1) for the fish.
7. The arrangement of claim 6, wherein the means for supplying fresh processing water comprises a pump that draws water from a greater depth in the surrounding sea.
8. The arrangement according to claim 6 or claim 7, wherein the means for supplying fresh processing water is arranged to retrieve cold fresh water from a watercourse.
9. A method for the treatment of farmed fish against parasites and diseases, wherein the fish is led from water having a first temperature to water having a second, lower temperature.