NO341228B1 - System and method for grading fish - Google Patents

Description

System and method for grading fish

The present invention relates to a system for grading offish while moving the fish from one place to another, for instance while loading fish from a fish cage to a fishing carrier, or while loading the fish from a boat to a processing plant or the similar on shore. The system may be used in any other situations where living fish should be transported from one place to another, and where grading is desirable. The system comprises at least two fish tanks for receiving the fish after the grading, means for draining off seawater, a transportation pipe system for removing fish from the first place and transporting the fish to the said fish tanks.

Known solutions for transporting fish for instance from a fish cage, involve either pumping the fish on board using a hydraulic vane pump which is placed inside the fish cage, or pumping by using a vacuum pump to lift the fish sufficiently. According to a known system, fish and water are lifted high above the highest deck and the force of gravity leads the fish over draining grids for seawater, which is led overboard, and then to the fish tanks via ducts. The fish farming industry tries to avoid the use of vacuum pumps as a means to transport live fish, as it induces stress in the fish.

If the fish is graded by size during transportation, the graders may be included in the draining grids for seawater, and placed at atmospheric pressure. A pump is needed to lift the fish onto the grader, and then it is flushed to the different tanks, usually by means of gravity fall. During the transportation the fish is thus subjected to under pressure, atmospheric pressure and over pressure. This requires many pumps and causes stress to the fish. Further the transport is usually in batch, and not continuously. NO 314611 describes such a system.

Continuously closed systems for transporting fish from one place to another are known, for instance from WO 2008/156370 and NO 314481. These systems are however not able to grade the fish by the size at the same time as the water is drained off.

By a "closed system" it is herein meant that the system is closed from the surroundings, meaning that air, gas, water and other elements can not enter or exit the system uncontrolled. Such systems are well-known, and a person skilled in the art would know how to construct and control such a system.

Infestation with sea lice including Lepeophtheirus salmonis and Caligus elongatus is considered to be one of the most important disease problems in farming of salmonids, especially in Atlantic salmon and rainbow traut. In addition to the costs that are associated with treatment, lower classification ratings of slaughtered fish and reduced growth rate due to reduced feed intake contribute to the economic losses ca used by sea lice.

In order to reduce the problems related to sea lice, some farmers add deaner fish, wrasses, into the fish net, and the wrasse will eat the sea lice, and thus dean the farmed fish. Wrasses such as ballan wrasse, do normally not exceed 60 cm, and thus their size is considerable smaller than grown farmed fish. When a fish farm is emptied and the farmed fish is transported to a processing plant, the wrasses should be paid special attention as they should be kept alive and transported to another fish plant. The wrasses are different from the farmed fish, in that they will not survive in fresh water, and thus they must be kept in sea water.

The main object of the invention is to reduce the number of times farmed fish needs to be handled, in order to reduce stress and possible injury of the fish. Another object of the invention is to reduce the use of different pressure while handling the fish.

Another object of the invention is to separate deaner fish from the farmed fish in a gentle way, keeping both the deaner fish and the farmed fish healthy and alive.

The present invention relates to a system and a method for grading fish while the fish is transported from one place to another, in a closed system.

The above mentioned objects are reached with a system and a method as described in the independent claims. Further advantageous features and alternative embodiments are given in the corresponding dependent claims.

The invention relates to a system for grading fish while moving the fish from one place to another. The system comprises at least two fish tanks for receiving the fish, a pipe system transporting the fish, means for draining off water, and means for creating and maintaining reduced pressure in the system. The system comprises further a grader separating fish of different size, wherein the pipe system is transporting the fish from a pool offish and water onto the means for draining off water and further to the grader, and finally from the grader and into the fish tanks. The fish tanks, means for draining off water, grader and pipe system is connected to each other in such a way that a closed system is made.

By "reduced pressure" it is herein meant pressure lower than the pressure of the surroundings. If the system is placed at a pressure of 1 bar, than any pressure below 1 bar, such as 0,9 bar, is a reduced pressure.

The "pool offish and water" may be a seine, trawl, fish cage, tank or similar. The ocean may also be a "pool of fish and water".

By "pipe-system" it is herein meant a system of pipes, hoses, tubes, or the similar connected to and from the different parts of the system, and ensuring that the fish and water will be transported to the desired places. The pipe system may be a continuous pipe or several discontinuous pipes, as other parts of the system may be placed between the pipwa. The pipes being part of the pipe system are not necessarily identical, and each pipe may be stiff or foldable, and have a given length or be telescopic. Each pipe must however be suitable for the intended use, and withstand a flow of water and fish without getting broken or plugged. Further, as it is to be used in a system operating with reduced pressure, it must withstand reduced pressure in the range of 0,5 -0,7 bar. The reduced pressure of the system is preferably about 0,5 bar which corresponds to suction height of 5 meters water column.

The pipe system may further comprise a pipe that runs down into the pool offish and water, and when the system is running and there is a reduced pressure inside the system, suction will arise in the pipe, and water and fish will start to flow into the pipe. This will continue as long as there is reduced pressure inside the system, and therefore a system according to the present invention will give a continuous flow of fish and water, in different from known batch systems.

The grader may have two parts, where the first part is draining off water and the second part is grading fish of different size. The water being separated from the fish in the first part, will be collected in a water tank and pumped out of the system.

The means for creating and maintaining reduced pressure in the system may comprise a valve connected to a pump for removing air in order to maintain the reduced pressure of the system. The valve may be placed by the grader, preferably at an upper part of the grader, such as at the upper part of a wall, or the ceiling.

The total volume offish and water transported into the system should correspond to the volume of water removed from the water tank, and the volume offish transported to the fish tanks. In this way the reduced pressure will be constant and stress induced to the fish will be reduced to a minimum.

The grader comprises at least one sorting grid, wherein the small fish falls through the grid, and the larger fish does not. A first fish tank is connected to the lower part of the grader and receives the smaller fish, and a second tank is connected to the upper part of the grader, and receives the larger fish. As the water will be drained off in the first part of the grid, the fish will be led into the fish tank with a minimum of water.

The sorting grid may be rows of rolls, wherein each roll are longitudinal and running in the transportation direction of the system. The rolls may be rotating, and thus assist the transport of the fish. The opening between two adjacent rolls will define the size of the fish that may pass through the sorting grid. The opening between two adjacent rolls may increase towards the outlet of the sorting grid, either by the design of each roll, or by the design of grader as such. This will assist in the transport of the fish as well as the grading.

The grader may comprise two or more sorting grids, and preferably the grids are arranged vertically above each other. The opening of each grid is smaller than the opening in a grid upstream. This means that the largest fish will not fall through any grid, and that the smallest fish will fall through all grids. If each grid is a row of rolls, an upper grid will have a larger opening between two adjacent rolls, than a lower grid, and thus the smallest fish will be collected at the lower part of the grader and the larger fish will be collected at the upper part.

The invention also relates to a method for grading fish while moving the fish from one place to another. The method comprises steps for collecting the fish to be graded in a pool offish and water, and placing a pipe system of a grading system into the pool. Then reduced pressure should be established in the pipe system, and water and fish will be sucked into the pipe system. The pipe system leads the fish and water to a means for draining off water, the water will be led to a water tank and the fish will be led onto a grader. The grader contains at least one sorting grid, and the fish will be sorted by size and led through the pipe system to different fish tanks. A valve for removing air is connected to a pump and arranged to create and maintain reduced pressure in the system. In order to maintain the reduced pressure, the volume of water removed from the water tank and the volume of air removed through the valve should equal the volume offish and water removed from the pool.

Detailed Description of the Embodiment shown in the Figure

The invention will now be described with the help of the enclosed figure, showing a principle diagram of a system according to the present invention. The different parts of the figure are not necessarily in scale to each other, as the figure is merely for illustrating the invention.

The following description of an exemplary embodiment refers to the drawing, and the following detailed description is not meant or intended to limit the invention. Instead, the scope of the invention is defined by the appended claims.

Reference throughout the specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of the subject matter disclosed. Thus, the appearance of the phrases "in one embodiment" or "in an embodiment" in various places throughout the specification is not necessarily referring to the same embodiment. Further, the particular features, structures or characteristics may be combined in any suitable manner in one or more embodiments.

The system shown in Figure 1 comprises at least two fish tanks 1, 2, a grader 3 and a pipe system including a pipe 4 running into a pool 5 offish and water. The pipe system, grader and fish tanks are connected to each other and constitute a closed system. The grader comprises a first part 3A where water is removed from the fish, and a second part 3B comprising a sorting grid 6 wherein the fish is graded by size. The sorting grid 6 has openings which allow small fish to pass, but not larger fish. The smaller fish is thus led into a fish tank 1, while the larger fish is led into another fish tank 2. Water which is separated from the fish is led to a water tank 7, and pumped out of the system by a pump (not shown). The water tank is also a part of the closed system.

In a preferred embodiment, the shown system is arranged on a fish carrier ship, and the pool 5 offish and water is a fish cage. The smaller fish to be sorted out are wrasses, and the larger fish is farmed salmon or trout and should be tåken to the shore for slaughtering and processing. The fish tank 2 for the larger fish is the hold of the fish carrier ship, and the fish tank 1 for the smaller fish is holding the wrasses. The fish tank 2 contains fresh water, possibly connected to a RSW system, and the fish tank 1 contains sea water to keep the wrasses healthy and well. In the shown embodiment there is a valve 8 arranged at the bottom offish tank 1, arranged to remove wrasses from the system and deliver them to another fish cage.

One end of the pipe 4, which is running into the pool 5 offish and water, is placed in the pool in such a way that water and fish may be sucked into the pipe. The other end of the pipe is connected to the grader 3, håving a first part 3A separating water and fish, and a second part comprising at least one sorting grid 6 which grades the fish by size. The first part of the grader is connected to the water tank 7, and the second part is connected to the fish tanks 1,2. All connections are tight in such a way that the system comprising the different parts, is closed.

In order to create and maintain a reduced pressure in the system, a valve 9 connected to a pump, is arranged in the grader or somewhere in the pipe system. As the system is closed, and all connections are tight, the valve may be placed at several places, but in order to avoid removal of water, it is preferred to arrange the valve at the grader, and more preferred to arrange it at the upper part of the grader.

When the system should be used, air is removed through the valve 9 until sufficiently reduced pressure is achieved, and water and fish will start to flow into the pipe and onto the grader. Once the system is running, the pumps removing air through the valve, and water from the water tank, are adjusted according to the volume of water and fish flowing into the system from the pool, in order to maintain the reduced pressure. These measurements and adjustments may be performed by well known methods which will be obvious to a person skilled of the art. The system is running continuously, and a constant flow of water and fish will enter the system. When the desired amount offish and water is transported from the pool 5 and the system should be closed down, the pump removing air is shut down, and the reduced pressure will gradually be reduced until it equals the pressure of the surroundings. All pumps and valves in connection with the system for loading and unloading are preferably controlled automatically, and may be controlled remotely, for instance by means of a computer.

The present system can also comprise or be connected to control and monitoring systems, and during loading, a catch measuring device may state the amount which comes on board and is guided to the desired tank.

Further, the temperature and amount offish in each tank can be logged and printed out, and also transferred via satellite to a buyer or an office onshore. Each fish tank logs its own history. This can also be complemented with information about position of the vessel, lifting height from the sea and on board during loading, seawater temperature, and also any relevant data which the fish buyer might wish.

Claims (8)

1. System for grading fish while moving the fish from a pool (5) of fish and water to at least two fish tanks (1, 2), wherein a pipe system runs from the pool (5) to means (3A) for draining off seawater, further to a grader (3) and from the grader to the respective fish tanks (1, 2) and in that the system is operated with reduced pressure, wherein the reduced pressure is achieved by a pump connected to a valve (9) arranged in the pipe system.

2. System according to claim 1,characterized in thatthe means for draining off seawater (3A) is a first part of the grader (3), and that a second part (3B) of the grader (3) comprises at least one sorting grid (6) grading fish of different size.

3. System according to claim 2,characterized in thatthe water being separated from the fish will be collected in a water tank (7), and pumped out of the system.

4. System according to any of the preceding claims,characterizedthe valve (9) is placed by the grader (3).

5. System according to claim 4,characterized in thatthe pumps for removing water from the water tank (7) and air through the valve (9) are adjusted according to the total volume offish and water flowing through the pipe system (4), in such a way that the reduced pressure is maintained.

6. System according to any one of claims 2 - 5,characterized in thatthe sorting grid (6) of the grader (3) comprises at least one row of rolls, wherein each roll is longitudinal and running in the transportation direction of the system.

7. System according to claim 7,characterized in thatthe opening between two adjacent rolls of the same grid is increasing towards the outlet of the grader.

8. Method for grading fish while moving the fish from one place to another with a system according to any one of the claims 1-7,characterized bycomprising the following steps: - arranging one part of the pipe system (4) into a pool (5) offish and water, containing the fish to be graded, - creating reduced pressure in the system by removing air through valve (9), until water and fish is flowing from the pool into the pipe system (4), and - controlling the pumps for removing air through valve (9) and water from the water tank (7) in order to maintain the negative pressure.