Method relating to pumping fish

Abstract

A method of reducing the amount of fish pumped by a fish pump, while maintaining a sufficient flow rate, such that the fish cannot swim back into the pump upstream, the method comprising the steps of: providing a device (100) for pumping fish, comprising: a main communication channel (120) through which water and fish are conveyed; a fish pump (110) comprising an inlet (110A) and an outlet (HOB), and arranged on the main communication channel (120) and configured to pump water and fish along the main communication channel (120); and an upstream bypass chamber (130) arranged on the main communication passage (120) upstream of the fish pump inlet (110A); wherein the upstream bypass chamber (130) is configured, in use, to mix a water flow into the main communication passage (120); providing fish and water to the main communication channel (120); operating the fish pump (110) to pump fish and water along the main communication channel (120); mixing the water flow into the main communication passage (120) at the upstream bypass chamber (130); this reduces the amount of pumped fish while maintaining a sufficient flow rate on the downstream side of the fish pump (110) so that the fish cannot swim upstream back to the fish pump outlet (HOB).

Description

Technical Field

[0001] The present invention relates to a method for pumping fish. More particularly, the present invention relates to a method for pumping anadromous fish. Background Art

[0002] In aquaculture, fish are often pumped to different locations for a variety of reasons. Fish may be pumped from one location to another to move the fish or to capture the fish when they are fully grown. In addition, fish may be pumped to a boat to delouse the fish and then pumped back into the water to continue growing. Fish are often pumped along with the water they live in, i.e., the pump moves a volume of water along with the fish.

[0003] During normal pumping of fish, the fish pump will run at its normal operating speed. This results in the water flow downstream of the pump being at the normal output flow rate.

[0004] If the operator or downstream process requires less or no pumping of fish for a period of time, the pump must switch to a slower operating speed or stop. This results in a slower than normal output flow rate for the water downstream.

[0005] If the fish being pumped are anadromous fish, i.e. they swim upstream, such as salmon, smelt and sturgeon, they may be able to swim faster than the slowed output flow rate and be able to swim back to the pump. This is highly undesirable as this may cause damage to the fish and / or the pump, especially when the pump speed is increased again.

[0006] Japanese Patent Document JPS6181321A discloses a solid material conveying device that is equipped with a rotary solid material conveying pump that pushes a liquid with an impeller and uses the liquid as a conveying medium to convey the solid material.

[0007] It is an object of the present invention to remedy or alleviate at least one of the disadvantages of the prior art, or at least to provide a useful alternative to the prior art.

[0008] This object is achieved by the features specified in the following description and the appended claims. Summary of the invention

[0009] According to a first aspect of the present invention, there is provided a method for reducing the amount of fish pumped by a fish pump while maintaining a sufficient flow rate so that the fish cannot swim upstream back to the pump, the method comprising the following steps: providing an apparatus for pumping fish, the apparatus comprising: a main communicating channel through which water and fish are conveyed; a fish pump comprising an inlet and an outlet, and the fish pump is arranged on the main communicating channel and configured to pump water and fish along the main communicating channel; and an upstream bypass chamber arranged on the main communicating channel upstream of the fish pump inlet; wherein the upstream bypass chamber is configured to mix a water flow into the main communicating channel in use, providing fish and water to the main communicating channel; operating the fish pump to pump the fish and water along the main communicating channel; characterized in that the water flow is mixed into the main communicating channel at the upstream bypass chamber; thereby reducing the amount of fish pumped, while maintaining a sufficient flow rate on the downstream side of the fish pump so that the fish cannot swim upstream back to the fish pump outlet.

[0010] The fish pump may be a vaneless centrifugal pump.

[0011] The upstream bypass chamber may include a central fluid communication passage having a diameter consistent with that of the main communication passage.

[0012] The central fluid communication channel may include a grille configured to define an outer boundary within the upstream bypass chamber to which fish can reach when passing through the upstream bypass chamber while allowing water to enter the central fluid communication channel through the grille.

[0013] The spacing of the grating may be suitably dimensioned such that fish pumped through the upstream bypass chamber in use cannot pass through the grating, and such that a sufficient volume of water can pass through the grating into the central fluid communication channel.

[0014] The upstream bypass chamber may include a conical diffuser configured to slow down the flow of water entering the main communication passage.

[0015] The upstream bypass chamber may include an expansion chamber configured to slow down the flow of water entering the main communication channel.

[0016] The bypass chamber may include a fine mesh configured to reduce a velocity of water flowing into the bypass chamber to be mixed into the main communication channel.

[0017] The main communication channel may include a first stop valve and a second stop valve configured to control the flow of water and fish in the main communication channel.

[0018] The apparatus may further include a make-up pump configured to pump water to the upstream bypass chamber.

[0019] The apparatus may further comprise a downstream bypass chamber arranged on the main communication channel downstream of the fish pump outlet; wherein the downstream bypass chamber is configured to remove water from the main communication channel during use so that the removed water can be recirculated to the upstream bypass chamber.

[0020] The apparatus may further include a make-up pump configured to pump water from the downstream bypass chamber to the upstream bypass chamber.

[0021] According to a second aspect of the present invention, there is provided a method for reducing the amount of fish pumped by a fish pump while maintaining a sufficient flow rate so that the fish cannot swim upstream back into the pump, the method comprising the following steps: providing an apparatus for pumping fish, the apparatus comprising: a main communicating channel through which water and fish are conveyed; a fish pump comprising an inlet and an outlet, and the fish pump is arranged on the main communicating channel and configured to pump water and fish along the main communicating channel; and an upstream bypass chamber arranged on the main communicating channel upstream of the fish pump inlet; wherein the upstream bypass chamber is configured to mix the water flow in use, and a downstream bypass chamber is arranged on the main communicating channel downstream of the fish pump outlet. ; wherein the downstream bypass chamber is configured to remove water from the main connecting channel during use so that the removed water can be recirculated to the upstream bypass chamber into the main connecting channel; provide fish and water to the main connecting channel; operate the fish pump to pump the fish and water along the main connecting channel; characterized in that water is removed from the main connecting channel at the downstream bypass chamber; the removed water is connected from the downstream bypass chamber to the upstream bypass chamber; and the removed water is mixed back into the main connecting channel at the upstream bypass chamber; thereby reducing the amount of fish pumped while maintaining a sufficient flow rate on the downstream side of the fish pump so that the fish cannot swim upstream back to the fish pump outlet.

[0022] The fish pump may be a vaneless centrifugal pump.

[0023] The upstream bypass chamber may include a central fluid communication passage having a diameter consistent with that of the main communication passage.

[0024] The central fluid communication channel may include a grille configured to define an outer boundary within the upstream bypass chamber to which fish may reach as they pass through the upstream bypass chamber while allowing water to enter the central fluid communication channel through the grille.

[0025] The spacing of the grating may be suitably dimensioned such that fish pumped through the upstream bypass chamber in use cannot pass through the grating, and such that a sufficient volume of water can pass through the grating into the central fluid communication channel.

[0026] The upstream bypass chamber may include a conical diffuser configured to slow down the flow of water entering the main communication passage.

[0027] The upstream bypass chamber may include an expansion chamber configured to slow down the flow of water entering the main communication channel.

[0028] The bypass chamber may include a fine mesh configured to reduce a velocity of water flowing into the bypass chamber to be mixed into the main communication channel.

[0029] The main communication channel may include a first stop valve and a second stop valve configured to control the flow of water and fish in the main communication channel.

[0030] The apparatus may further include a make-up pump configured to pump water to the upstream bypass chamber.

[0031] The apparatus may further include a make-up pump configured to pump water from the downstream bypass chamber to the upstream bypass chamber. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Embodiments of the present invention will now be described with reference to the following drawings, in which:

[0033] Figure 1 A hydraulic diagram of a device for pumping fish is shown;

[0034] Figure 2 Shown in Figure 1 Bypass valves used in equipment; and

[0035] Figure 3 A hydraulic diagram showing an alternative example of an apparatus for pumping fish.

[0036] For the sake of clarity, some elements may not have reference numerals in some drawings. Those skilled in the art will appreciate that the drawings are only primary drawings. The relative proportions of the various elements may also be distorted.

[0037] Detailed description with attached drawings

[0038] In the following description, for the sake of brevity, all fluid communication connections are not described in detail. It is assumed that those skilled in the art can understand the fluid connections from the accompanying drawings without further explanation.

[0039] Figure 1 An example apparatus 100 for pumping upstream migratory fish is shown. The apparatus 100 includes a fish pump 110, which includes an inlet 110A and an outlet 110B. The fish pump 110 in the example currently described is a vaneless centrifugal pump. However, it should be understood that other suitable pump designs may be used, such as but not limited to Coanda pumps or paddle wheel pumps. The fish pump 110 is configured to pump water and fish on a main communication channel 120. The main communication channel 120 is a series of pipes suitable for transporting fish therein. The main communication channel 120 is connected to an upstream bypass chamber 130, the purpose and structure of the upstream bypass chamber 130 will be explained in more detail later.

[0040] Still reference Figure 1 , the fish and water are supplied to the main communication channel 120 on the inlet 110A side of the pump, and are pumped by the pump 110 to continue on the main communication channel 120 on the outlet 110B side of the pump 110 .

[0041] If the downstream process requires less fish, or the operator decides to reduce the flow of fish through the pump 110, additional water can be provided to the pump 110 by mixing the additional water with the fish and water in the main communication channel 120 on the inlet 110A side of the pump. The mixing occurs in the upstream bypass chamber 130.

[0042] In this case, additional water is provided and flows along the bypass communication channel 131 to the main communication channel 120. In order to enhance the flow of water along the bypass communication channel 131, a pump ( Figure 1 131) pumps water along the bypass communication channel 131. It should be understood that water can be provided without the use of a pump. For example, water can be provided from a water reservoir located at a position physically higher than the bypass chamber, thereby utilizing hydrostatic pressure to provide mixing of water into the flow in the main communication channel 120.

[0043] When additional water is provided to the pump 110 as described herein, the amount of fish pumped will decrease if the pump 110 is maintained at the same pumping speed. In this way, the water flow rate at the outlet 110b can be maintained constant regardless of the amount of fish pumped.

[0044] In other words, in the above example, pump 110 is initially loaded with water and fish and set to an operating speed. This results in a water flow at outlet 110B having a particular speed. If pump 110 were to be slowed down to reduce the amount of fish being pumped, the speed of the water flow at outlet 110B would decrease. If the speed of the water flow at the outlet decreases sufficiently, anadromous fish may be able to swim back toward pump outlet 110B, potentially causing damage to pump 110 and / or the fish.

[0045] However, as described above, by providing additional water to the main communication channel 120 on the inlet 110A side of the pump 110, the amount of fish pumped is reduced while maintaining the flow rate at the outlet 110B. This ensures that the flow rate at the outlet 110b can be kept high enough so that the fish cannot swim back to the outlet 110B.

[0046] It should be understood that the upstream bypass chamber 130 can be any suitable connection between the bypass communication channel 131 and the main communication channel 120 so that the water flow in the bypass communication channel 131 can be mixed with the flow of water and fish in the main communication channel 120.

[0047] Reference now Figure 2 , further details of the preferred upstream bypass chamber 130 can be seen. As previously mentioned, the upstream bypass chamber 130 is arranged in a straight line on the main communication channel 120. In this regard, the inlet 130A and the outlet 130B are connected to the main communication channel 120. Within the upstream bypass chamber 130, a central fluid communication channel 132 is provided, and when the upstream bypass chamber 130 is assembled in the main communication channel 120, the central fluid communication channel 132 provides a continuation of the main communication channel 120, so that fish can enter the upstream bypass chamber 130 at the inlet 130A and leave at the outlet 130B. In this case, the diameter of the central fluid communication channel 132 is consistent with the diameter of the main communication channel 120. That is, they have the same or substantially similar diameters.

[0048] The upstream bypass chamber 130 also includes a conical diffuser 133 arranged to be fluidly connected to the bypass communication channel 131. The purpose of the conical diffuser 133 is to slow down the speed of the water flow from the bypass communication channel 131 when entering the upstream bypass chamber 130 to prevent stress on the fish in the central fluid communication channel 132.

[0049] In this case, it is highly desirable that the water flow from the bypass communication channel 131 mixes smoothly with the water flow in the central fluid communication channel 132. To this end, the upstream bypass chamber 130 includes an expansion chamber 134 into which the flow from the conical diffuser 133 reaches. The central fluid communication channel 132 is provided with a grating defining an outer boundary that fish can reach within the central fluid communication channel 132 while allowing water to enter the central fluid communication channel 132 from the expansion chamber 134. It should be understood that the spacing of the grating must be small enough so that the pumped fish cannot pass through the grating. However, the spacing of the grating must be large enough so that a sufficient volume of water can enter the central fluid communication channel 132 from the expansion chamber 134.

[0050] Still reference Figure 2, the upstream bypass chamber 130 includes another flow reduction mechanism located between the conical diffuser 133 and the expansion chamber 134. The other flow reduction mechanism is a fine mesh 135, which further reduces the velocity of water entering the expansion chamber 134 from the conical diffuser 133.

[0051] Figure 3 An alternative apparatus 1000 for pumping anadromous fish is shown. Figure 1 and Figure 2 In the examples shown in the same reference numerals are used to indicate Figure 3 , but with "0" added. For example, Figure 1 and Figure 2 The pump 110 in the example shown in FIG. Figure 3 The number marked in the table is 1100.

[0052] The apparatus 1000 includes a fish pump 1100 including an inlet 1100A and an outlet 1100B. As in the previously described examples, the fish pump 1100 in the currently described example is a vaneless centrifugal pump. However, it should be understood that other suitable pump designs may be used, such as but not limited to a Coanda pump or a paddle wheel pump. The fish pump 1100 is configured to pump water and fish from a fish start point 1110 to a fish end point 1120 on a main communication channel 1200. The main communication channel 1200 is a series of pipes suitable for transporting fish therein.

[0053] from Figure 3 As can be seen in FIG. 1 , the main communication channel 1200 is provided with a first stop valve 1201 and a second stop valve 1202. These are provided to allow control of the flow within the main communication channel 200. Depending on the type of pump 1100 used in other examples, the first stop valve 1201 and the second stop valve 1202 may not be required. For example, a vacuum pump (push-pull type) or an ejector pump (Coanda type) may not require the first stop valve 1201 and the second stop valve 1202.

[0054] The main communication channel 1200 is connected to the upstream bypass chamber 1300. The fish and water are supplied to the main communication channel 1200 on the inlet 1100A side of the pump 1100, and are pumped by the pump 1100 to continue on the main communication channel 1200 on the outlet 1100B side of the pump 1100.

[0055] The pump 1100 may be supplied with additional water by mixing the additional water with the fish and water in the main communication channel 1200 on the inlet 1100A side of the pump. The mixing is performed in the upstream bypass chamber 1300. The additional water is supplied and flows to the main communication channel 1200 along the bypass communication channel 1310.

[0056] To enhance the flow of water along the bypass communication passage 1310, water is pumped along the bypass communication passage 1310 by a supplemental pump 1400. Likewise, it should be understood that in some alternative examples, the supplemental pump 1400 may not be necessary.

[0057] The device 1000 includes a plurality of stop valves arranged at various positions. In this case, a third stop valve 1203, a fourth stop valve 1204, a fifth stop valve 1205 and a sixth stop valve 1206 are provided in the example currently described. It should be understood that more or less stop valves may be provided in other examples, depending on the specific arrangement and the desired function.

[0058] Still reference Figure 3 , a third stop valve 1203 and a fourth stop valve 1204 are provided to select a water source to the supplementary pump 1400. In this case, the fourth stop valve 1204 provides for the delivery of water from the supplementary water source A to the supplementary pump 1400 when opened.

[0059] Alternatively, water may be supplied to the supplementary pump 1400 from near the outlet 1100B of the fish pump 1100. In this case, some water is sucked from the main communication passage 1200 at the downstream bypass chamber 1500 by the pump 1400. In the example described so far, the downstream bypass chamber 1500 is identical in structure to the upstream bypass chamber 1300, i.e., both the upstream bypass chamber 1300 and the downstream bypass chamber 1500 are similar. Figure 2 However, the downstream bypass chamber 1500 is arranged in the apparatus 1000 so that water is removed from the main communication passage 1200 at the downstream bypass chamber 1500 , rather than being added to the main communication passage 1200 as at the upstream bypass chamber 1300 .

[0060] Although in the presently described example, upstream bypass chamber 1300 and downstream bypass chamber 1500 are identical in structure, this is not critical. That is, in alternative examples, upstream bypass chamber 1300 may be structurally different from downstream bypass chamber 1500.

[0061] By providing a downstream bypass chamber 1500, such as Figure 3As shown, a fluid flow loop can be formed from the outlet 1100B of the fish pump 1100 back to the inlet 1100B. If the downstream operation or the operator does not need fish for a period of time, the downstream bypass chamber 1500 and the supplementary pump 1400 can be used to circulate water back to the main communication channel 1200. In this operation mode, the third stop valve 1203 and the fifth stop valve 1205 are opened, and the supplementary pump 1400 works. The open third stop valve 1203 provides fluid communication between the downstream bypass chamber 1500 and the supplementary pump 1400. The open fifth stop valve 1205 provides fluid communication between the supplementary pump 1400 and the upstream bypass chamber 1300, so no matter how the water supply from the source A or the downstream bypass chamber 1500 is, the fifth stop valve 1205 needs to be opened to allow the supplementary pump 1400 to pump water to the upstream bypass chamber 1300.

[0062] The continuous loop of very fast flowing water from outlet 1100B to inlet 1100A results in the fish pump 1100 not taking any fish from upstream of the upstream bypass chamber 1300 (i.e., the fish starting point 1110) because the entire pumping capacity (volume) of the fish pump 1100 is consumed by pumping the recirculating water. Most importantly, during said recirculation, the flow rate of water in the main communication channel 1200 at the outlet 1100B of the pump (i.e., between the outlet 1100B and the downstream bypass chamber 1500) remains high enough that fish cannot swim upstream to the pump. This therefore allows the operator to stop the flow of fish through the pump while only maintaining a high enough water flow rate so that fish downstream of the pump cannot swim back upstream and reach the pump, which, as described above, could cause damage to the pump and / or the fish.

[0063] It will be appreciated that the fluid flow loop from the outlet 1100B back to the inlet 1100A of the fish pump 1100 may also be used to simply reduce the amount of fish being pumped, rather than completely stopping the pumping of fish. The volume flow rate required by the supplemental pump 1400 to stop the flow of fish into the fish pump 1100 will depend on the specifications and configuration of the fish pump 1100 and the apparatus 1000 as a whole, i.e., pipe sizes, etc. Similarly, the volume flow rate required by the supplemental pump 1400 to reduce the amount of fish being pumped will also depend on the specifications and configuration of the fish pump 1100 and the apparatus 1000 as a whole, i.e., pipe sizes, etc.

[0064] Still reference Figure 3 , the sixth shut-off valve 1206 can be used to spray water from the device 1000 to point B. For example, if the device 1000 is being cleaned, the sixth shut-off valve 1206 can be used. Alternatively, if there is a fault and water should be sprayed from the device 1000, the sixth shut-off valve 1206 can be opened to allow an exit path for the water. Alternatively, in some examples, point B can be another water source, where the sixth shut-off valve is opened to provide fluid communication between the alternative water source and the upstream bypass valve 1300.

[0065] As previously described, the downstream bypass chamber 1500 may be similar or identical to the upstream bypass chamber 1300. In this regard, the physical features of the upstream bypass chamber 1300 are also present in the downstream bypass chamber 1500.

[0066] That is, the downstream bypass chamber 1500 also includes a conical diffuser, an expansion chamber and a fine mesh ( Figure 3 However, since the downstream bypass chamber 1500 operates in the opposite sense to the upstream bypass chamber 1300, i.e., the downstream bypass chamber 1500 removes water from the main communication channel 1200 rather than adding water thereto, the purpose of the tapered diffuser, the enlarged chamber, and the fine mesh is to allow water to be removed from the main communication channel 1200 at a slow flow rate. The tapered diffuser then accelerates the flow because it narrows the flow area to the diameter of the piping system through which the flow must pass in the circulation loop.

[0067] It is highly advantageous to remove water at a slow flow rate at the main communication passage 1200 because the high velocity of water flowing out of the main communication passage 1200 will cause the fish to be drawn toward the supplemental pump 1400 when the fish are in the downstream bypass chamber 1500. In some examples, this may cause blockage at the downstream bypass chamber 1500 and thus affect the performance of the apparatus 1000. Additionally or alternatively, drawing the fish toward the supplemental pump 1400 within the downstream bypass chamber 1500 may cause stress to the fish, which is highly undesirable.

Claims

1. A method of reducing the amount of fish pumped by a fish pump while maintaining a sufficient flow rate so that the fish cannot swim upstream back into the pump, the method comprising the steps of: An apparatus (100, 1000) for pumping fish is provided, comprising: A main communication channel (120, 1200), through which water and fish are transported; a fish pump (110, 1100) comprising an inlet (110A, 1100A) and an outlet (110B, 1100B), the fish pump (110, 1100) being arranged on the main communication channel (120, 1200) and configured to pump water and fish along the main communication channel (120, 1200); and An upstream bypass chamber (130, 1300) is arranged on the main communication channel (120, 1200) upstream of the fish pump inlet (110A, 1100A); wherein the upstream bypass chamber (130, 1300) is configured to mix water flow into the main communication channel (120, 1200) during use, Providing the fish and water to the main communication channel (120, 1200); operating the fish pump (110, 1100) to pump the fish and water along the main communication channel (120, 1200); Characterized in that the water flow is mixed into the main communication channel (120, 1200) at the upstream bypass chamber (130, 1300); The amount of fish pumped is thereby reduced, while a sufficient flow rate is maintained on the downstream side of the fish pump (110, 1100) so that the fish cannot swim upstream back to the fish pump outlet (110B, 1100B).

2. The method according to claim 1, wherein: The fish pump (110, 1100) is a bladeless centrifugal pump.

3. The method according to claim 1 or 2, wherein: The upstream bypass chamber (130, 1300) includes a central fluid communication passage (132), the diameter of which is consistent with that of the main communication passage (120, 1200).

4. The method according to claim 3, wherein: The central fluid communication channel (132) includes a grille configured to define an outer boundary within the upstream bypass chamber (130, 1300) so that fish can reach the outer boundary when passing through the upstream bypass chamber (130, 1300) while allowing water to enter the central fluid communication channel (132) through the grille.

5. The method according to claim 4, wherein: The spacing of the grating is suitably sized so that fish pumped through the upstream bypass chamber (130, 1300) in use cannot pass through the grating, and so that a sufficient volume of water can pass through the grating into the central fluid communication channel (132).

6. A method according to any preceding claim, wherein: The upstream bypass chamber (130, 1300) includes a conical diffuser (133) configured to slow down the flow of water entering the main communication channel (120, 1200).

7. A method according to any preceding claim, wherein: The upstream bypass chamber (130, 1300) includes an expansion chamber (134) configured to slow down the flow of water entering the main communication channel (120, 1200).

8. A method according to any preceding claim, wherein: The bypass chamber (130, 1300) includes a fine mesh configured to reduce the velocity of water flow entering the bypass chamber (130, 1300) to be mixed into the main communication channel (120, 1200).

9. A method according to any preceding claim, wherein: The main communication channel (1200) includes a first stop valve (1201) and a second stop valve (1202), and the first stop valve (1201) and the second stop valve (1202) are configured to control the flow of water and fish in the main communication channel (1200).

10. A method according to any preceding claim, wherein: The apparatus (1000) further comprises a supplementary pump (1400) configured to pump water to the upstream bypass chamber (1300).

11. The method according to any one of claims 1 to 10, wherein: The device (1000) further comprises a downstream bypass chamber (1500), wherein the downstream bypass chamber (1500) is arranged on the main communication channel (1200) downstream of the fish pump outlet (1100B); The downstream bypass chamber (1500) is configured to remove water from the main communication channel (1200) during use, so that the removed water can be recycled to the upstream bypass chamber (1300).

12. The method according to claim 11, wherein: The apparatus (1000) further comprises a supplementary pump (1400) configured to pump water from the downstream bypass chamber (1500) to the upstream bypass chamber (1300).

13. A method of reducing the amount of fish pumped by a fish pump (1100) while maintaining a sufficient flow rate so that the fish cannot swim upstream back into the pump (1100), the method comprising the steps of: An apparatus (1000) for pumping fish is provided, comprising: a main communication channel (1200), through which water and fish are transported; a fish pump (1100), comprising an inlet (1100A) and an outlet (1100B), and the fish pump (1100) is arranged on the main communication channel (1200) and is configured to pump water and fish along the main communication channel (1200); and An upstream bypass chamber (1300) arranged on the main communication channel (1200) upstream of the fish pump inlet (1100A); wherein the upstream bypass chamber (1300) is configured to mix the water flow in use, A downstream bypass chamber (1500) is arranged on the main communication channel (1200) downstream of the fish pump outlet (1100B); wherein the downstream bypass chamber (1500) is configured to remove water from the main communication channel (1200) during use, so that the removed water can be recirculated to the upstream bypass chamber (1300) and enter the main communication channel (1200); and provide fish and water to the main communication channel (1200); operating the fish pump (1100) to pump the fish and water along the main communication channel (1200); characterised in that water is removed from the main communication channel (1200) at the downstream bypass chamber (1500); communicating the removed water from the downstream bypass chamber (1500) to the upstream bypass chamber (1300); and mixing the removed water back into the main communication channel (1200) at the upstream bypass chamber (1300); The amount of fish being pumped is thereby reduced while maintaining a sufficient flow rate on the downstream side of the fish pump (1100) so that the fish cannot swim upstream back to the fish pump outlet (1100B).

14. The method according to claim 13, wherein: The fish pump (1100) is a bladeless centrifugal pump.

15. The method according to claim 13 or 14, wherein: The upstream bypass chamber (1300) includes a central fluid communication passage (132), and the diameter of the central fluid communication passage (132) is consistent with that of the main communication passage (1200).

16. The method according to any of claims 13 to 15, wherein: The central fluid communication channel (132) includes a grille configured to define an outer boundary within the upstream bypass chamber (1300) that fish can reach when passing through the upstream bypass chamber (1300) while allowing water to enter the central fluid communication channel (1200) through the grille.

17. The method according to any of claims 13 to 16, wherein: The spacing of the grating is dimensioned appropriately so that fish pumped through the upstream bypass chamber (1300) in use cannot pass through the grating, and so that a sufficient volume of water can pass through the grating into the central fluid communication channel (1200).

18. The method according to any of claims 13 to 17, wherein: The upstream bypass chamber (1300) includes a conical diffuser (133) configured to slow down the flow of water entering the main communication channel (1200).

19. The method according to any of claims 13 to 18, wherein: The upstream bypass chamber (1300) includes an expansion chamber configured to slow down the flow of water entering the main communication channel (1200).

20. The method according to any of claims 13 to 19, wherein: The bypass chamber (1300) includes a fine mesh configured to reduce the velocity of water flow entering the bypass chamber (1300) to be mixed into the main communication channel (1200).

21. The method according to any of claims 13 to 20, wherein: The main communication channel (1200) includes a first stop valve (1201) and a second stop valve (1202), and the first stop valve (1201) and the second stop valve (1202) are configured to control the flow of water and fish in the main communication channel (1200).

22. A method according to any of claims 13 to 21, wherein: The apparatus (1000) further comprises a supplementary pump (1400) configured to pump water to the upstream bypass chamber (1300).

23. A method according to any of claims 13 to 22, wherein: The apparatus (1000) further comprises a supplementary pump (1400) configured to pump water from the downstream bypass chamber (1500) to the upstream bypass chamber (1300).

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