Exterminating marine organisms

Abstract

A system 18 for exterminating marine organisms 32 (e.g., sea lice) comprising an incoming flow path 30 onto a filter drum 10 trapping parasites entrained in the flow, at least one killing mechanism 22

Description

This invention relates to systems and methods for exterminating marine organisms. The invention relates particularly to systems and methods for killing ectoparasites, for example parasite larvae, in farmed fish enclosures. Farming allows fish to be raised in seawater environments until they reach a required market size. Examples of farmed fish include marine species such as salmon, sea trout, sea bream, sea bass, halibut, and turbot as well as freshwater species such as freshwater trout, carp, and tilapia. Farmed fish are typically confined in sea cages or net pens. Although a net pen confines the fish being farmed, it does not prevent parasites such as sea lice from drifting into the pen and possibly infesting the fish. Parasite infestations can cause significant damage to farmed fish as the parasites feed on the skin, blood, and mucus of the fish to survive. When attached, the parasites cause open wounds and weaken the fish, resulting in unmarketable products. Traditional methods for controlling sea lice infestation typically involve the use of chemical treatments. These methods include using active chemicals in a bath treatment or added into the fish feed. While these treatments may be effective to some extent, they can contaminate the environment and parasites can develop resistance to chemical or biochemical agents over time. Mechanical and biological control methods have been explored as alternatives to chemical treatments. Mechanical methods such as waterjets remove the parasites from fish but can cause damage to the fish in doing so, such as scale removal. Biological methods include introducing natural predators to sea lice into the aquaculture environment. However, introducing predators can disrupt the local marine ecosystem, affecting other species. Consequently, it is evident that parasites should ideally be removed from fish pens before they attach to the fish. There have been many such proposals in the prior art. For example, WO 2021 / 038179 discloses a filter apparatus for filtering parasites from water. Pressurised air is injected through an air injection port in a conduit, creating a pressure differential in the conduit between a water inlet and outlet, causing water to be drawn into the water inlet, through the conduit and into the filter. Although this apparatus is beneficial in some respects, the filter can become blocked when full of parasites and thus, must be removed from the apparatus for frequent cleaning. NO 345976 discloses a pelagic crustacean parasite collection device. The device is transparent and is provided with a flashing light source to attract pelagic crustacean parasites. Parasites that approach the device follow water flow through an inlet in the device and are carried with the water flow towards a pump. The parasites are then filtered from the water flow by a filter on the pump. As with WO 2021 / 038179, NO 345976 requires the filter to be cleaned and replaced once blocked, which can be slow and inefficient. In addition, as the collection device must be attached to a frame mooring of the pen, the device does not have the ability to traverse the pen to collect further parasites. This limits the catching area and ultimately, the number of parasites that can be caught. In an even more cumbersome solution, NO 337292 discloses a device for collecting and destroying lice present in water. The device comprises a submerged container that is connected to a pump designed to suck water and lice into the container through slits or openings in the container. Once the parasites have been sucked into the container, they pass through a mill where they are ground. The grinder may also employ UV radiation. Although NO 337292 can be considered an effective termination device, the remnants of the lice must be collected in a separate collection unit using a fine strainer. This is a laborious process as the water and lice must be drained from the collection tank, discharging the water to the sea while lice residues are removed and transported away. NO 20140640 discloses a system for harming parasites present in water. Parasites are attracted to light emitted from devices attached to the system. Once the parasites are lured toward a conductive surface of the device, the device emits a series of electrical pulses that kill or weaken the parasites. However, using electrical pulses may inadvertently affect other aquatic life in the aquaculture environment that may be sensitive to changes in electrical conductivity. In addition, marine infrastructure that requires electrical currents can be complex and costly. Against this background, the invention resides in a method of exterminating marine organisms. The method comprises entraining the organisms in a flow of water, trapping the organisms on a filter interposed in the flow, exterminating the organisms when trapped on the filter and purging the exterminated trapped organisms from the filter. The method may further comprise moving the filter, when supporting the trapped organisms, before exterminating the trapped organisms. Advantageously, the trapped organisms may be conveyed, whilst supported by the filter, to a kill zone at which the trapped organisms are exterminated. To exterminate the trapped organisms, they may be exposed to at least one killing mechanism in the kill zone. Conveniently, the trapped organisms may be exposed to at least two killing mechanisms that employ ultraviolet and ultrasonic energy respectively in either order or simultaneously. Before extermination, the trapped organisms may be moved out of the flow. The filter may also be moved, when supporting the exterminated trapped organisms, before purging the exterminated organisms. The filter may be moved relative to the flow, in a direction transverse to a direction of the flow. Conveniently, the filter may be moved filter continuously or stepwise. The exterminated trapped organisms may be purged from a purge zone by conveying an outgoing flow of water through the filter. The outgoing flow may comprise water of an incoming flow that carried the entrained organisms to the filter, wherein the incoming flow and the outgoing flow move in a common flow direction. The method may also include presenting a first side of the filter to the incoming flow and an opposed second side of the filter to the outgoing flow. Advantageously, the method may also comprise rotating the filter after trapping the organisms and before purging the exterminated trapped organisms. The filter may be rotated about an axis transverse to the flow. For example, the method may include passing the flow through a drum that defines the filter, the flow moving in a direction transverse to a central longitudinal axis of the drum. The inventive concept embraces a corresponding system for exterminating marine organisms. The system comprises an incoming flow path configured to direct an incoming flow of water to a filter interposed in the incoming flow path, the filter being arranged to trap organisms entrained in the incoming flow; at least one killing mechanism configured to exterminate the organisms trapped by the filter; and an outgoing flow path configured to direct an outgoing flow from the filter to entrain the exterminated organisms, thereby to purge the exterminated organisms from the filter. The at least one killing mechanism may comprise an ultraviolet emitter, an ultrasonic transducer, an infrared emitter, a laser, a roller, a scraper and / or an auger press. Advantageously, the system may further comprise at least one imaging system positioned to capture images of the organisms trapped by the filter. The or each imaging system may be positioned to capture images when the organisms trapped by the filter are out of the water. Aptly, the or each killing mechanism may be controllable in response to signals from the or each imaging system. The system may be configured such that the outgoing flow path receives water conveyed to the filter via the incoming flow path. The incoming flow path and the outgoing flow path may be mutually aligned with a common flow direction. The system may also include a housing that houses the filter and that comprises an inlet channel defining the incoming flow path and an outlet channel defining the outgoing flow path. Conveniently, the housing may be suspended from a float and / or movable relative to a body of water to be driven through the body of water by thrust of the outgoing flow. The filter may be movable relative to the housing from a trap zone opposed to the inlet channel to a purge zone opposed to the outlet channel. Fittingly, the filter may be movable in a direction transverse to the incoming flow, pivotable about an axis extending transverse to the incoming flow. The filter may be a drum through which the incoming flow passes to become the outgoing flow. Advantageously, the drum may be movable from the trap zone to the purge zone via a kill zone at which the or each killing mechanism is located. The system may also comprise an impeller disposed in the drum to drive the incoming and outgoing flows, and / or an impeller disposed in the incoming flow path and / or in the outgoing flow path to drive the incoming and outgoing flows. Conveniently, two or more systems may be positioned in a body of water at similar or respectively different depths to increase the volume of treated water. In order that the invention may be more readily understood, reference will now be made, by way of example, to accompanying drawings in which: Figure 1 is a perspective view of a drum filter in a first embodiment of the invention; Figure 2 is a side view of the drum filter of Figure 1; Figure 3 is a schematic side view of an extermination system comprising a housing around the drum filter of Figures 1 and 2; Figure 4 is a schematic side view of an extermination system corresponding to Figure 3 but including an imaging system and not necessarily including the housing; Figures 5a to 5d are a sequence of schematic side views that illustrate stepwise movement of the drum filter of the extermination system of Figure 3; Figure 6 is a schematic side view of a variant of the extermination system in which flow through the drum filter is driven by a downstream impeller; Figure 7 is a schematic side view of a further variant of the extermination system in which flow through the drum filter is driven by an upstream impeller; Figure 8 is a schematic side view of a further variant of the extermination system in which imaging is performed out of water; Figure 9 is a schematic side view of a further variant of the extermination system in which water is pumped onto the drum filter; Figure 10 is a schematic plan view of the extermination system of Figure 3 suspended in water by a rotating frame supported by a float or other supporting member; Figure 11 is a schematic side view corresponding to Figure 10; Figure 12 is a schematic side view of the extermination system of Figure 3 suspended from a float or other supporting member; Figure 13 is a schematic plan view of a further embodiment of an extermination system; and Figure 14 is a schematic side view corresponding to Figure 13. Referring firstly to Figures 1 and 2 of the drawings, Figure 1 shows a filter of an extermination system according to an embodiment of this invention and Figure 2 shows a side view of the filter of Figure 1. In this example, the filter is a cylindrical or tubular structure, or drum 10, through which incoming water flow passes. The drum 10 extends along a central longitudinal axis A, around which the drum 10 is rotationally symmetrical. A foraminous tubular wall 12 of the drum 10, which may be penetrated by holes, slits, or other openings, includes a longitudinal series of raised circumferential projections designed to trap organisms entrained in water flowing across and through the wall 12. Typically, the projections lie parallel to one another and are mutually spaced between 100pm to 250pm. The closely spaced projections enable the capture of ectoparasites in their larval stage as well as pre-adults and adult stages of the ectoparasites that detach from host fish and are present in the water column. However, the closely spaced projections inhibit the capture of small fish. The projections may be arranged in parallel circumferential loops in planes orthogonal to axis A or helically, wrapping around the drum 10 from one end of the drum 10 to the other end of the drum 10. Other arrangements and spacings are also possible. Different screening input filters (not shown) may also be used to screen particles such as feed particles, organisms, larger organisms that are above a target size. The drum 10 has internal bars 14 that lie parallel to one another and to axis A. The bars 14 are equiangularly spaced around axis A and extend between end flanges 16 that lie in planes orthogonal to axis A. The bars 14 support the tubular wall 12 of the drum 10 while allowing water to flow through the spaces between the bars 14. Figures 3 and 4 show schematics of an extermination system 18 including the drum 10. In Figure 3, the drum 10 is encased in a housing 20 and is driven for continuous or stepwise rotation about axis A relative to the housing 20. The housing 20 includes an inlet channel 26 and an outlet channel 42. The inlet channel 26 receives and guides an incoming water flow 30 to the drum 10 and the outlet channel 42 expels and guides an outgoing water flow 46 from the drum 10. In this example, the drum 10 also contains an impeller 34 that drives the flow of water along the inlet and outlet channels 26, 42 and through the drum 10. The impeller 34 is mounted on a web 36 that is fixed relative to the housing 20, here intersecting axis A of the drum 10. The drum 10 is therefore rotatable around the impeller 34 and the web 36. When the impeller 34 is driven, it generates a drop in pressure on an inlet side, shown to the right in Figures 3 and 4, and an increase in pressure on an outlet side, shown to the left in Figures 3 and 4. This drives the incoming flow 30 along an incoming flow path 38. The incoming flow path 38 directs the incoming flow 30 into the inlet channel 26 toward a trap zone on the outside of a first, upstream side 28 of the tubular wall 12 of the drum 10, opposed to the incoming flow 30. Thus, marine organisms 32 such as ectoparasites entrained in the incoming flow 30 (shown here as black squares, when alive) are sucked onto, trapped by and held against the external projections on the tubular wall 12 of the drum 10. The flow of water continues through and out of the drum 10 on an outgoing flow path 38 that directs the outgoing flow 46 through and away from a second, downstream side 40 of the drum 10 at a purge zone diametrically opposed to the trap zone on the first side 28 of the drum 10. As the outgoing flow 46 travels in the same direction as the incoming flow 30, the outgoing flow 46 impinges on the inside of the tubular wall 12 on the second side 40 of the drum 10 and then flows through the tubular wall 12. The force of that inside-out water flow through the tubular wall 12 propels dead organisms 44 (shown here as white circles) away from the tubular wall 12 after they have been exterminated. This propulsion purges the dead organisms 44 from the drum 10 and out of the outlet channel 42, entrained in the outgoing flow 46. While the incoming flow 30 of water pins the live organisms 32 against the tubular wall 12 of the drum 10, the drum 10 rotates anticlockwise as shown to carry the organisms 32 from the trap zone to a kill zone where the organisms 32 are exposed to one or more killing mechanisms. Here, the organisms 32 are exposed to the or each killing mechanism for a sufficient dwell time to kill most or substantially all of the organisms 32 that are supported on the drum 10 in the kill zone. In this example, the kill zone is located out of the incoming water flow 30, and may indeed be in an air-filled upper chamber within the housing 20 as will be explained, but can instead be submerged as shown here. In this example, the system 18 includes two different killing mechanisms angularly spaced around the outside of the drum 10 on an upstream portion of the drum 10 to kill the organisms 32 trapped on the drum 10. The extermination mechanisms may include an ultrasonic (US) transducer 22 that kills the organisms 32 by exposing them to high-frequency sound waves and an ultraviolet emitter 24 that kills the organisms 32 by exposing them to ultraviolet (UV) radiation. Alternatively, or additionally, lasers or mechanical extermination mechanisms such as rollers, scrapers, and / or auger presses may be used to kill the organisms 32. In the example shown in Figure 4, the system 18 further includes a camera 48 positioned to obtain images of the organisms 32 trapped on the drum 10. Here, the camera 48 is shown positioned between the trap zone and the kill zone to image the live organisms 32. A camera could instead, or additionally, be positioned between the kill zone and the purge zone to image the dead organisms 44. Feedback from the images captured by the or each camera 48 can be used to control the killing mechanisms 22, 24 and / or the drum 10 to make extermination more effective, for example by adjusting the dwell time in the kill zone or by adjusting the intensity, the wavelengths or the mix of the killing mechanisms 22, 24. The drum 10 supporting the dead organisms 44 continues to turn relative to the flow of water until the dead organisms 44 are purged from the drum 10 at the purge zone. Once at the purge zone, the dead organisms 44 are expelled from the tubular wall 12 of the drum 10 by conveying the outgoing flow 46 of water through the wall 12. The outgoing flow 46 comprises the incoming flow 30 that carried the entrained live organisms 32 to the drum 10. The process of trapping, exterminating and purging organisms repeats as the drum 10 turns and successive portions of the tubular wall 12 of the drum 10 move through each respective zone. In this respect, Figures 5a to 5d exemplify how the drum 10 can turn in a stepwise manner, it being understood that continuous rotation of the drum 10 is also possible. In Figure 5a, live organisms 32 are shown entrained in the incoming flow 30 of water. The incoming flow 30 is directed towards a first side 28 of the drum 10 as the flow of water travels through the wall 12 of the drum 10 in a direction transverse to the central longitudinal axis A of the drum 10. The organisms 32 are thereby trapped by the wall 12 of the drum 10 as shown in Figure 5b. After a period of time sufficient to trap a desired volume of organisms 32 in the trap zone, the drum 10 turns through an angle sufficient to move the trapped organisms 32 from the trap zone to the kill zone as shown in Figure 5c. In the kill zone, UV and US are employed to kill the trapped organisms 32. After a dwell time sufficient to kill the organisms 32 in the kill zone, the drum 10, supporting the now dead organisms 44, turns through an angle sufficient to move the dead organisms 44 from the kill zone to the purge zone, as shown in Figure 5d. The drum 10 turns relative to the flow of the water while the flow of water continues through the drum 10, such that the outgoing flow 46 impinges on the inner side of the wall 12 of the drum 10 at the purge zone. The force of the water flowing out through the wall 12 from within the drum 10 purges the trapped dead organisms 44 from the drum 10. Figures 6 to 9 show variants of the extermination system 18. In Figures 6 and 7, the impeller 34 is disposed outside the drum 10. Specifically, Figure 6 shows the impeller 34 disposed in an outlet channel 42 downstream of the drum 10 whereas Figure 7 shows the impeller 34 disposed in an inlet channel 26 upstream of the drum 10. In Figure 8, the housing 20 traps an air pocket 52 that accommodates an upper portion of the drum 10. The level of the air / water interface 54 may be controlled using sensors and pumps to compress air in the air pocket 52. As the drum 10 turns relative to the housing 20 and the flow of water, the live organisms 32 trapped in the trap zone are exposed to US in the kill zone at 22 for a desired dwell time. Exposure to US may take place underwater as shown. The organisms 32 exposed initially to US are shown here as white squares. The drum 10 continues to turn, exiting the water flow and entering the air pocket 52. The camera 48 captures images of the organisms 32 and the organisms 32 are then subject to UV at 24 for a desired dwell time. Turning the drum 10 through the air pocket 52 speeds extermination as the organisms 32 are taken out of the water, improving optical kill methods. The air pocket 52 is also beneficial for clearer imaging using the camera 48, may be beneficial for UV transmission, and may also be beneficial for keeping the drum 10 clean. The drum 10, supporting the now dead organisms 44, continues to turn, exiting the air pocket 52 and re-entering into the water flow. The water that continues to flow through the drum 10 purges the dead organisms 44 from the drum 10. In the example of Figure 9, the drum 10 is shown floating partially out of water. In this embodiment, water is driven from a target zone at a depth at which the parasite larvae are present and is pumped over the drum 10. As the pumped water impinges on the drum 19, organisms 32 entrained in the flow are trapped by the wall 12 of the drum 10. As the water flows over and through the drum 10 on a path offset laterally from the axis A, the momentum of the flow drives rotation of the drum 10 in the corresponding angular direction, moving trapped organisms 32 from the trap zone to the kill zone. In this example, the kill zone again is located out of the water, aiding extermination and imaging as explained above. It will be apparent that the flow of water into, through and out of a filter such as the drum 10 will generate thrust when an extermination system 18 of the invention is in a body of water, especially where that flow is substantially unidirectional. The thrust will act in the direction of the flow and the reaction to that thrust will tend to propel the extermination system in a direction opposed to the flow. If desired, the thrust acting on the extermination system 18 can be resisted by supporting the system 18 on a fixed mounting, for example fixed to the structure of a fish pen that surrounds and defines the body of water. Conversely, Figures 10 to 12 show embodiments that exploit the thrust to propel one or more extermination systems 18 through a body of water, hence increasing the volume of water in which organisms 32 can be trapped and killed. Figures 10 and 11 show two extermination systems 18 of the invention suspended via their housings 20 from a frame that hangs from a float 62 or other support in a body of water 60. The float 62 is typically tethered in a fixed position with multiple mooring lines extending to an edge of the pen to prevent it from drifting in the water. The frame has an inverted T shape, comprising two arms 64 extending generally horizontally in mutually opposed directions from a generally vertical central member 66. The arms 64 terminate at their free ends in upright outer members 68 that suspend the extermination systems 18 from the arms 64. At its upper end, the central member 66 joins to the float 62 via a hub that allows the frame to rotate relative to the float 62 about an upright axis along which the central member 66 extends. The hub can accommodate a swivel connection that allows power and data signals to pass through from a topside control. The arms 64 of the frame support respective extermination systems 18 that are spaced horizontally from the central member 66. The extermination systems 18 are oriented so that their outlet channels 42 are directed transversely or orthogonally relative to the respective arms 64 in opposite directions in plan view and hence in a common circumferential direction about the upright axis of rotation. Consequently, the thrust acting on the extermination systems 18 drives rotation of the frame about the upright axis relative to the float 62. In operation, the extermination systems 18 therefore sweep around circular paths through the body of water 60 to increase the volume of water in which organisms 32 are trapped and killed. In this example, the extermination systems 18 are held at respectively different depths in the water because the outer members 68 have different lengths. Thus, the extermination systems 18 follow different circular paths stacked one above the other, further increasing the swept volume of water. In a variant, members of the frame supporting the extermination systems 18 could be variable in length to change the depth and / or radius of the swept path, allowing one or more extermination systems 18 to track through an optimum target zone in a body of water 60. Figure 12 shows an extermination system 18 of the invention suspended via its housing 20 from a float 62 or other support in a body of water 60. Here, the extermination system 18 is suspended by a swinging, pivoting support 66 such as a rod or a flexible cable that hangs from the float 62. As the housing 20 takes in water containing live organisms through the inlet channel 26 and expels water containing dead organisms through the outlet channel 42, the system 18 is thrust through the water. The support 66 allows the system 18 to move through the water in a random or controlled pattern such as a figure of eight or a circle. Thus, extermination coverage increases as the system 18 not only moves back and forth, but also side to side. In Figures 10 to 12, fixed-length mooring lines acting on the float 62 or other support could be replaced with variable-length lines extending to a set of smart winches. Such an arrangement could move the float 62 or other support linearly through X-, Y- and / or Z-axis cartesian coordinates, thereby allowing the or each extermination system 18 to traverse a greater proportion of the body of water 60. Turning finally to Figures 13 and 14, these figures exemplify an alternative filter arrangement. In this embodiment, the filter 10 is a flat, circular disc-like structure through which the incoming water flow passes to trap organisms entrained in the flow. The filter 10 turns about a central axis A that is orthogonal to the plane of the filter 10 Two impellers 34 drive the flow of water, namely, a first impeller 34 disposed on a first side of axis A that drives an incoming flow to the upstream face of the filter 10 and a second impeller 34 disposed on a second, opposite side of axis A that drives an outgoing flow away from the upstream face of the filter 10. As the force of the water flow generated by the first impeller 34 traps organisms on the filter 10 at a trap zone, the filter 10 turns, either continuously or in a stepwise manner, from the trap zone to a kill zone at which killing mechanisms such as US 22 and UV emitters 24 facing the upstream side of the filter 10 act on the organisms trapped against the filter 10. The trap zone and the kill zone could be coincident, at the same or overlapping angular positions relative to axis A. This example also includes a camera 48 to image trapped organisms in the kill zone. Once the organisms have been exterminated in the kill zone, the filter 10 turns to convey the dead organisms to a purge zone at which the flow driven by the second impeller 34 propels the dead organisms away from the filter 10. Now substantially clear of dead organisms, the filter 10 continues to turn into and through the trap zone and the process repeats. Many other variations are possible within the inventive concept. For example, the system may also include at least one antifouling mechanism to inhibit growth of fouling on the surface of the filter. The antifouling mechanism may, for example, employ UV and / or US. Additionally, the system could include at least one sensor configured to measure water salinity. Measuring water salinity may be used to determine the optimum depth to place the system as parasite larvae are known to thrive beneath a halocline where brackish water meets seawater. The system could also include a plurality of impellers disposed inside and / or outside the drum. For example, an impeller could be disposed in the outlet channel downstream of the drum and another impeller could be disposed in the inlet channel upstream of the drum. Indeed, one or more impellers can be in any position or in any combination relative to the drum or other filter. Moreover, in open pens where tidal flows are experienced, those flows could be used to assist or to replace the impeller-driven flows envisaged above. For example, tidal assistance could be employed to carry live organisms toward the filter and / or to carry exterminated organisms from the filter to decompose naturally in the water surrounding the pen. Such dilution reduces the concentration of waste in the pen.

Claims

1. A method of exterminating marine organisms, the method comprising:entraining the organisms in a flow of water;trapping the organisms on a filter interposed in the flow;exterminating the organisms when trapped on the filter; andpurging the exterminated trapped organisms from the filter.

2. The method of Claim 1, further comprising moving the filter, when supporting the trapped organisms, before exterminating the trapped organisms.

3. The method of Claim 2, comprising conveying the trapped organisms, supported by the filter, to a kill zone at which the trapped organisms are exterminated.

4. The method of Claim 3, further comprising exposing the trapped organisms to at least one killing mechanism in the kill zone.

5. The method of Claim 4, comprising exposing the trapped organisms to at least two killing mechanisms that employ ultraviolet and ultrasonic energy respectively in either order or simultaneously.

6. The method of any of Claims 2 to 5, comprising moving the trapped organisms out of the flow before exterminating them.

7. The method of any of Claims 2 to 6, further comprising moving the filter, when supporting the exterminated trapped organisms, before purging the exterminated organisms.

8. The method of any of Claims 2 to 7, comprising moving the filter relative to the flow.

9. The method of Claim 8, comprising moving the filter in a direction transverse to a direction of the flow.

10. The method of any preceding claim, comprising moving the filter continuously.

11. The method of any of Claims 1 to 9, comprising moving the filter stepwise.

12. The method of any preceding claim, comprising purging the exterminated trappedorganisms from a purge zone by conveying an outgoing flow of water through the filter.

13. The method of Claim 12, wherein the outgoing flow comprises water of an incoming flow that carried the entrained organisms to the filter.

14. The method of Claim 13, wherein the incoming flow and the outgoing flow move in a common flow direction.

15. The method of Claim 13 or Claim 14, further comprising presenting a first side of the filter to the incoming flow and an opposed second side of the filter to the outgoing flow.

16. The method of any preceding claim, further comprising rotating the filter after trapping the organisms and before purging the exterminated trapped organisms.

17. The method of Claim 16, comprising rotating the filter about an axis transverse to the flow.

18. The method of any preceding claim, comprising passing the flow through a drum that defines the filter, the flow moving in a direction transverse to a central longitudinal axis of the drum.

19. A system for exterminating marine organisms, the system comprising:an incoming flow path configured to direct an incoming flow of water to a filter interposed in the incoming flow path, the filter being arranged to trap organisms entrained in the incoming flow;at least one killing mechanism configured to exterminate the organisms trapped by the filter; andan outgoing flow path configured to direct an outgoing flow from the filter to entrain the exterminated organisms, thereby to purge the exterminated organisms from the filter.

20. The system of Claim 19, wherein the at least one killing mechanism comprises an ultraviolet emitter, an ultrasonic transducer, an infrared emitter, a laser, a roller, a scraper and / or an auger press.

21. The system of Claim 19 or Claim 20, further comprising at least one imaging system positioned to capture images of the organisms trapped by the filter.

22. The system of Claim 21, wherein the or each imaging system is positioned to capture images when the organisms trapped by the filter are out of the water.

23. The system of Claim 21 or Claim 22, wherein the or each killing mechanism is controllable in response to signals from the or each imaging system.

24. The system of any of Claims 19 to 23, configured such that the outgoing flow path receives water conveyed to the filter via the incoming flow path.

25. The system of Claim 24, wherein the incoming flow path and the outgoing flow path are mutually aligned with a common flow direction.

26. The system of any of Claims 19 to 25, further comprising a housing that houses the filter and that comprises an inlet channel defining the incoming flow path and an outlet channel defining the outgoing flow path.

27. The system of Claim 26, wherein the housing is suspended from a float.

28. The system of Claim 26 or Claim 27, wherein the housing is movable relative to a body of water to be driven through the body of water by thrust of the outgoing flow.

29. The system of any of Claims 24 to 28, wherein the filter is movable relative to the housing from a trap zone opposed to the inlet channel to a purge zone opposed to the outlet channel.

30. The system of Claim 29, wherein the filter is movable in a direction transverse to the incoming flow.

31. The system of Claim 30, wherein the filter is pivotable about an axis extending transverse to the incoming flow.

32. The system of Claim 31, wherein the filter is a drum through which the incoming flow passes to become the outgoing flow.

33. The system of Claim 32, wherein the drum is movable from the trap zone to the purge zone via a kill zone at which the or each killing mechanism is located.

34. The system of Claim 32 or Claim 33, further comprising an impeller disposed in the drum to drive the incoming and outgoing flows.

35. The system of any of Claims 19 to 33, further comprising an impeller disposed in the incoming flow path and / or in the outgoing flow path to drive the incoming and outgoing flows.

36. Two or more systems of any of Claims 19 to 35, positioned in a body of water at similar or respectively different depths.The following amendments have been added to the claims as follows:04 07 2518Claims1. A method of exterminating marine organisms, the method comprising:5 entraining the organisms in a flow of water;trapping the organisms on a filter interposed in the flow;moving the filter relative to the flow, when supporting the trapped organisms,10 before exterminating the organisms when trapped on the filter; andpurging the exterminated trapped organisms from the filter.15 2. The method of Claim 1, comprising conveying the trapped organisms, supported bythe filter, to a kill zone at which the trapped organisms are exterminated.

3. The method of Claim 2, further comprising exposing the trapped organisms to at least one killing mechanism in the kill zone.

204. The method of Claim 3, comprising exposing the trapped organisms to at least two killing mechanisms that employ ultraviolet and ultrasonic energy respectively in either order or simultaneously.25 5. The method of any preceding claim, comprising moving the trapped organisms out ofthe flow before exterminating them.

6. The method of any preceding claim, further comprising moving the filter, when supporting the exterminated trapped organisms, before purging the exterminated30 organisms.

7. The method of Claim 1, comprising moving the filter in a direction transverse to a direction of the flow.35 8. The method of any preceding claim, comprising moving the filter continuously.04 07 259. The method of any of Claims 1 to 7, comprising moving the filter stepwise.

10. The method of any preceding claim, comprising purging the exterminated trapped organisms from a purge zone by conveying an outgoing flow of water through the filter.

511. The method of Claim 10, wherein the outgoing flow comprises water of an incoming flow that carried the entrained organisms to the filter.

12. The method of Claim 11, wherein the incoming flow and the outgoing flow move in a 10 common flow direction.

13. The method of Claim 11 or Claim 12, further comprising presenting a first side of the filter to the incoming flow and an opposed second side of the filter to the outgoing flow.15 14. The method of any preceding claim, further comprising rotating the filter aftertrapping the organisms and before purging the exterminated trapped organisms.

15. The method of Claim 14, comprising rotating the filter about an axis transverse to the flow.2016. The method of any preceding claim, comprising passing the flow through a drum that defines the filter, the flow moving in a direction transverse to a central longitudinal axis of the drum.25 17. A system for exterminating marine organisms, the system comprising:an incoming flow path configured to direct an incoming flow of water to a filter interposed in the incoming flow path, the filter being arranged to trap organisms entrained in the incoming flow;30at least one killing mechanism configured to exterminate the organisms trapped by the filter, wherein the filter is movable relative to the killing mechanism; andan outgoing flow path configured to direct an outgoing flow from the filter to35 entrain the exterminated organisms, thereby to purge the exterminated organismsfrom the filter.04 07 2518. The system of Claim 17, wherein the at least one killing mechanism comprises an ultraviolet emitter, an ultrasonic transducer, an infrared emitter, a laser, a roller, a scraper and / or an auger press.

519. The system of Claim 17 or Claim 18, further comprising at least one imaging system positioned to capture images of the organisms trapped by the filter.

20. The system of Claim 19, wherein the or each imaging system is positioned to capture 10 images when the organisms trapped by the filter are out of the water.

21. The system of Claim 19 or Claim 20, wherein the or each killing mechanism is controllable in response to signals from the or each imaging system.15 22. The system of any of Claims 17 to 21, configured such that the outgoing flow pathreceives water conveyed to the filter via the incoming flow path.

23. The system of Claim 22, wherein the incoming flow path and the outgoing flow path are mutually aligned with a common flow direction.2024. The system of any of Claims 17 to 23, further comprising a housing that houses the filter and that comprises an inlet channel defining the incoming flow path and an outlet channel defining the outgoing flow path.25 25. The system of Claim 24, wherein the housing is suspended from a float.

26. The system of Claim 24 or Claim 25, wherein the housing is movable relative to a body of water to be driven through the body of water by thrust of the outgoing flow.30 27. The system of any of Claims 22 to 26, wherein the filter is movable relative to thehousing from a trap zone opposed to the inlet channel to a purge zone opposed to the outlet channel.

28. The system of Claim 27, wherein the filter is movable in a direction transverse to the 35 incoming flow.07 2529. The system of Claim 28, wherein the filter is pivotable about an axis extending transverse to the incoming flow.

30. The system of Claim 29, wherein the filter is a drum through which the incoming flow 5 passes to become the outgoing flow.

31. The system of Claim 30, wherein the drum is movable from the trap zone to the purge zone via a kill zone at which the or each killing mechanism is located.10 32. The system of Claim 30 or Claim 31, further comprising an impeller disposed in thedrum to drive the incoming and outgoing flows.

33. The system of any of Claims 17 to 31, further comprising an impeller disposed in the incoming flow path and / or in the outgoing flow path to drive the incoming and outgoing15 flows.

34. Two or more systems of any of Claims 17 to 33, positioned in a body of water at similar or respectively different depths.

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