Biomass camera accessory

Abstract

A system (100) for capturing images of one or more fish, the system comprising: an optical imaging device (101) configured to capture images of the one or more fish, a guard structure (106) attached to the optical imaging device (101), wherein the guard structure (106) is positioned outside of a field of view of the optical imaging device (101) such that the guard structure (106) at least partially surrounds the field of view of the optical imaging device (101). The guard structure (106) is separated from the optical imaging device (101) such that the field of view of the optical imaging device (101) at the guard structure (106) is larger than a size of the one or more fish to be imaged.

Description

[0001] BIOMASS CAMERA ACCESSORY

[0002] Field of Disclosure

[0003] The present application relates to a structure for assisting with the capturing of images of fish, and in particular but not limited to a structure for assisting with the capturing of images of fish in a fish farm.

[0004] Background

[0005] In both land-based and sea-based fish farming, it is common practice to perform welfare and other grading checks on the fish at various stages of the lifecycle of the fish. These welfare and grading checks may include, for example, biomass measurements, size measurements, a count of the number of fish in a batch, etc. Such measurements can be used for a variety of purposes, such as feed optimisation, growth measurements, and harvesting detection.

[0006] Some systems and devices for grading and / or counting organisms in water require capturing an image of the fish, and analysing (e.g. via software algorithms) the images of the fish to estimate or determine the welfare or grading measurements. However, such image-based systems generally require capturing a full image of each fish to be measured. In other words, a fish must fit fully within the field of view of the camera in order for the e.g. biomass of the fish to be measured. As a result, fish farms, and in particular fish farms with a higher stocking density, encounter difficulties when attempting to utilise such systems, as the fish may often approach too closely to the camera. When the fish are too close to the camera, they may not fit within the camera’s field of view, preventing or reducing the accuracy of the measurements.

[0007] Additionally, some fish farms, such as land-based fish farms, may produce a steady state current due to the constant flow of water through the tank. Generally, fish exposed to a steady state current for a prolonged period may match their swim speed to the current flow. As a result, the fish may appear stationary within the tank. Such behaviour can result in further difficulties in performing the grading measurements and / or welfare checks on the fish, e.g. due to fish becoming stationary in front of the camera and blocking its view of other fish in the tank.

[0008] For these and other reasons, the Applicant has recognised a need for an improved system for capturing images of fish, for example as part of a system for performing fish welfare measurements. Summary

[0009] Aspects and preferred features are outlined in the accompanying claims.

[0010] Aspects of the present disclosure generally provide a structure for underwater image capturing devices, such as subsea or underwater camera systems, configured to maintain fish at at least a minimum distance to facilitate the capturing of images of whole or entire fish. Aspects of the present disclosure may therefore improve the accuracy of image analysis for e.g. calculated average biomass measurements (and other welfare indicators) by providing a greater rate of image frames that include images of a whole fish.

[0011] According to a first aspect of the present disclosure, there is provided a system for capturing images of one or more fish, the system comprising: an optical imaging device configured to capture images of the one or more fish; and a guard structure attached to the optical imaging device, wherein the guard structure is positioned outside of a field of view of the optical imaging device such that the guard structure at least partially surrounds the field of view of the optical imaging device; wherein the guard structure is separated from the optical imaging device such that the field of view of the optical imaging device at the guard structure is larger than a size of the one or more fish to be imaged.

[0012] Advantageously, the guard structure may prevent or discourage fish from approaching the (optical) imaging device. As such, by positioning the guard structure at a suitable distance in front of the imaging system, the fish may be maintained at at least a minimum distance away from the imaging system sufficient for the fish to fit wholly within the image frame. Thus, the guard structure may reduce a stocking density of fish in immediate proximity to the imaging device without disrupting the device’s field of view. This is particularly advantageous in areas of relatively high fish density, such as fish farms.

[0013] The optical imaging device may be any suitable imaging device, for example a camera such as a stereoscopic camera or any other type of camera device.

[0014] The system may comprise an attachment structure for attaching the guard structure to the optical imaging device, and one or more connecting structures extending between the guard structure and the attachment structure. The one or more connecting structures may comprise a plurality of connecting bars. In implementations, one or more of the plurality of connecting bars are not parallel to one another. By connecting the guard structure to the imaging device (via the attachment structure) with non-parallel connecting bars, the stability of the guard structure may be enhanced.

[0015] The guard structure may be any shape. In some implementations, the guard structure is circular or oval, to reduce the risk of injury to the fish on any corners of the guard structure. As such, the one or more connecting structures, the guard structure and the attachment structure form a cylindrical shape or conical shape.

[0016] In an implementation, the guard structure and the attachment structure are the same shape, and optionally the attachment structure is smaller than the guard structure. Alternatively, the guard structure and attachment structure may be different shapes.

[0017] A separation between adjacent connecting bars of the plurality of connecting bars may be greater than a size of the fish to be imaged. By providing the connecting bars with a separation distance greater than the size of the fish, the risk of injury to the fish (e.g. due to the fish becoming stuck or trapped by the bars) may be reduced. In implementations, one or more of the plurality of connecting bars are removably attached to the guard structure and the attachment structure. For example, the guard structure and attachment structure may each be provided with pre-determined attachment points (e.g. holes, receivers, screws, etc.) for the connection bars, and the separation between the bars may be controlled by removing one or more of the connection bars or connecting additional connection bars. Alternatively, the separation between adjacent connecting bars of the plurality of connecting bars may be smaller than a size of the fish to be imaged, to thereby reduce the probability of a fish swimming between the imaging device and the guard structure.

[0018] The attachment structure (and therefore the guard structure) may be removably attached to the optical imaging device. Additionally or alternatively, the attachment structure may be fixed to the imaging device, and the guard structure may be detached from the imaging device by disconnecting the connecting structure or bars from the guard structure and / or from the attachment structure.

[0019] The system may comprise netting between the guard structure and the attachment structure, to further discourage the ingress of fish between the guard structure and the imaging device. Alternatively, the connecting structure may comprise a single casing or housing that radially surrounds the field of view of the imaging device between the attachment structure and the guard structure.

[0020] One or more of the guard structure, attachment structure and connecting member(s) may be red, orange or yellow. Bright colours such as these may be more visible to fish, and therefore further discourage the approach of fish towards the imaging device.

[0021] One or more of the guard structure, attachment structure and connecting member(s) may comprise a material denser than water. For example, they may comprise a metal such as aluminium or stainless steel.

[0022] The system may be configured to perform welfare measurements based on the images of the one or more fish. The welfare measurements may comprise, but are not limited to biomass measurements, size measurements, and wound detection.

[0023] The system may comprise a perforated cover positioned between the guard structure and the optical imaging device, configured to prevent the ingress of small fish between the guard structure and the optical imaging device. The cover may be a net or mesh material. In an implementation, the cover may be provided between the guard structure and the attachment structure. Optionally, the cover may be provided about a perimeter of the system about an outside edge of the one or more connection bars, e.g. to thereby prevent fish from swimming between adjacent connection bars. The cover may be provided about some or all of the perimeter of the system.

[0024] According to a second aspect of the present disclosure, there is provided a guard structure for an underwater optical imaging device, the guard structure configured in use to be positioned outside of a field of view of the optical imaging device such that the guard structure at least partially surrounds the field of view of the optical imaging device; and wherein the guard structure is configured in use to be separated from the optical imaging device such that the field of view of the optical imaging device at the guard frame is larger than a size of the one or more fish to be imaged.

[0025] The guard structure may be provided with or without the imaging device, e.g. for attachment to a pre-existing imaging device. The guard structure may therefore comprise an attachment structure for attaching the guard structure to an underwater optical imaging device and one or more connecting structures extending between the guard structure and the attachment structure.

[0026] However, the guard structure does not need to be attached directly to the imaging device. Instead, and for example, the guard structure may be attached to or around a viewing window of a water tank, e.g. in a land-based fish farm, such that images for welfare measurements can be captured by the imaging device through the viewing window.

[0027] Thus, according to a third aspect of the present disclosure, there is provided a system comprising: a tank for holding a body of water with one or more fish; a viewing window in the tank; and a guard structure for an underwater optical imaging device connected to or around the viewing window, the guard structure configured in use to be positioned outside of a field of view of the optical imaging device such that the guard structure at least partially surrounds the field of view of the optical imaging device; and wherein the guard structure is configured in use to be separated from the optical imaging device such that the field of view of the optical imaging device at the guard frame is larger than a size of the one or more fish to be imaged.

[0028] Brief Description of the Figures

[0029] Some preferred embodiments of the invention will now be described, by way of example only and with reference to the accompanying drawings, in which:

[0030] Figure 1 illustrates an example imaging system according to the present disclosure.

[0031] Figures 2-4 illustrate further views of the example imaging system according to the present disclosure.

[0032] Figure 5 illustrates a further example imaging system according to the present disclosure.

[0033] Figures 6-8 illustrate further views of the further example imaging system according to the present disclosure.

[0034] Figures 9A and B illustrate a further example imaging system according to the present disclosure. Figures 10A and B illustrate a further example imaging system according to the present disclosure.

[0035] Figures 11A and B illustrate a further example imaging system according to the present disclosure.

[0036] Figures 12A and B illustrate a further example of a cage or frame for an imaging system according to the present disclosure.

[0037] Detailed Description of the Preferred Embodiments

[0038] Figure 1 depicts an example imaging system 100 according to the present disclosure. The system 100 comprises an image capturing device 101 and a structure, cage or frame 102. The image capturing or imaging device 101 may be, for example, an underwater or subsea camera or other device configured to capture images of one or more fish. The image capturing device 101 may comprise hardware or software systems configured to perform image analysis and determine various estimates or measurements to assist with the grading of the fish, such as biomass measurements, size measurements, or various other welfare checks such as wound detection. Alternatively, the image capturing device may be configured to transmit or transfer the captured images to an external computing system or device for such image analysis.

[0039] In implementations, the image capturing device may be a camera such as a stereoscopic camera, i.e. with two or more lenses each with a separate image sensor or film frame, or any other camera suitable for capturing images of fish. A stereographic camera may be used for stereo photography. Images of fish captured with a stereographic camera may facilitate more accurate welfare measurements (e.g. biomass measurements) of the fish in some image analysis processes.

[0040] The image capturing device 101 may be attached or attachable to the frame 102. It will be understood that frame 102 may be detachable and re-attachable to the image capturing device 101. Additionally or alternatively, the frame 102 may be provided separately from the image capturing device 101. For example, in a land-based fish farm, a tank may comprise a viewing window, and the frame 102 may be attached to an inside surface of the viewing window, such that the image capturing device 101 may be used to capture images from an outside surface of the viewing window.

[0041] The frame 102 comprises an attachment structure or ring 104 configured to attach or connect the frame 102 to the image capturing device 101. The attachment structure 104 may be attached to the image capturing device 101 via any suitable means, for example screws, bolts, clamps, adhesive, etc.

[0042] Frame 102 also comprises a guard structure or ring 106. The guard structure 106 is configured to maintain fish at at least a minimum distance from the image capturing device 101 , to thereby improve the rate of frames that include images of whole or entire fish, e.g. to facilitate more accurate image analysis of the fish. The minimum distance may be a distance sufficient for the fish to be imaged to fit wholly within the field of view of the image capturing device 101. It will therefore be understood that the dimensions of the frame 102 may vary depending on e.g. the field of view of the particular imaging or camera system, the species of fish, life stage of the fish, and / or average expected size of the fish. For example, a smaller species of fish or fish at an earlier stage of their life cycle (and which generally have a smaller size than older members of their species) may be able to approach more closely to the image capturing device 101 while remaining wholly within the field of view of the imaging device.

[0043] Additionally, guard structure 106 is dimensioned such that it does not encroach on a field of view of the image capturing device 101 , in order to avoid restricting or reducing the field of view of the image capturing device (and therefore the image capturing device’s ability to capture images of the fish). In other words, the size of the guard structure 106 may be sufficient that, when positioned at the intended or desired distance from the image capturing device 101 , the field of view of the image capturing device 101 falls completely within the guard structure 106. It will be understood that the field of view of image capturing devices such as camera systems typically form a cone or pyramidal shape, such that the field of view of the imaging device expands as the distance from the lens increases. As such, the size (e.g. radius) of the guard structure 106 may vary based on the aspect ratio and minimum distance for the image capturing device 101.

[0044] In some implementations, the image capturing device 101 may disregard outer edges of the field of view. For example, in a stereoscopic camera system, the image capturing device 101 may only utilise the overlapping areas of the fields of view of the lenses for any later image analysis. In such implementations, the guard structure 106 may infringe of the field of view of the image capturing device 101 , as long as it remains outside of the area of the field of view used for the later image analysis (e.g. the overlapping area of the field of view of the two or more lenses).

[0045] The guard structure 106 is depicted in Figure 1 as a circular structure, however it will be understood that the guard structure 106 may be provided in any desired shape, including but not limited to circles, ovals, triangles, squares, rectangles, pentagons, hexagons, etc. or irregular shapes. Round or smooth shapes such as circles, ovals, etc. may advantageously reduce the risk of injury to the fish, e.g. resulting from impact with a corner of the guard structure 104. Alternatively, square guard structures may provide the most efficient structure for pyramidal viewing fields, as they may be dimensioned to precisely match the size of the viewing field. The attachment structure 102 may also be provided in any desired shape. In implementations, the attachment structure may be the same shape as the guard structure 104, or it may be provided with a different shape. Similarly, the dimensions of the attachment structure 102 may be the same or approximately the same as the guard structure 104, or they may be different (e.g. larger or smaller) than the corresponding dimensions of the guard structure 104.

[0046] The attachment structure 104 and the guard structure 106 are connected via plurality of connecting spokes or bars 110. The connecting bars 110 may be inserted into pre-formed holes 108, slits, openings or other receptacles provided in the attachment structure 104 and the guard structure 106. The connecting bars provide two primary functions. Firstly, they connect the guard structure 106 to the attachment structure 104, to thereby position the guard structure 106 at the suitable or desired distance from the image capturing device 101. Secondly, they may deter or prevent the ingress of fish between the image capturing device 101 and the guard structure 106. The number and spacing of the connecting bars 110 may therefore be selected based on the size of the fish to be imaged. For example, while system 100 is depicted with a connecting bar 110 provided in every second hole 108, for smaller fish a connecting bar may be provided in every hole 108, while for larger fish a connecting bar 110 may be provided in every third hole 108. The spacing between the connecting bars 110 may be selected such that they are sufficiently close for the fish to view the connecting bars 110 as an obstacle, but sufficiently far apart that the fish will not become stuck, trapped or otherwise harmed by the connecting bars 110 if they do attempt to swim between the image capturing device 101 and the guard structure 106. For example, the gap between the adjacent bars 110 may be slightly larger than the fish being imaged to reduce the likelihood of a fish becoming stuck between adjacent bars. Alternatively, the gap may be smaller than the fish to be imaged, such that the fish are unable to swim between the adjacent bars. In addition or alternatively to the connection bars 110, the system 100 may comprise a solid connecting structure, housing or cover between the attachment structure and the guard structure (e.g. such that the attachment structure 104, guard structure 106 and connecting structure form a hollow cylinder without any radial gaps in the frame 102), or a netting material (e.g. positioned between adjacent connecting bars 110). Optionally, the connecting structure or housing may be perforated or otherwise have one or more radial openings, to allow water to pass through the connecting structure. The solid connecting structure and / or netting may further reduce the likelihood of fish swimming between the image capturing device 101 and the guard structure 106. In contrast, the use of connecting bars 110 rather than e.g. netting or a solid connecting structure may further reduce the impact of any currents or water resistance on the frame 102, thereby enhancing the ease of use of the system for an end user.

[0047] The frame 102 may be formed from any suitable material. In implementations, a material that is denser than water may be used, to improve the ease of handling of the system by the end user when underwater. For example, the frame 102 may comprise one or more of aluminium, stainless steel, copper, etc. Similarly, the frame 102 may be formed from a material that is resistant to rusting or corroding in water, or otherwise comprise a coating or protective layer to protect the frame 102 from water damage.

[0048] The frame 102 may be coloured to improve detection by fish. For example, colours such as reds and oranges are typically the most visible colours in shallow water (and therefore in smaller tanks), whereas blues and purples may be more visible in deeper water and / or in larger tanks.

[0049] Figures 2 and 3 respectively provide front and top views of the imaging system 100. Like reference numerals are provided in these figures.

[0050] Figure 4 depicts example dimensions of the system 100 in millimetres. The total axial length C of the frame 102 may be 435mm, while a separation B between the image capturing device 101 and the guard structure 104 may be 365mm. At this distance, and for example, the guard structure 104 may have a diameter A of 670mm. As discussed above, the dimensions of the frame 102 may vary based on several factors, and it will therefore be understood that these dimensions are provided as illustrative examples only, and are not intended to be limiting in nature. In some implementations, the minimum distance D for imaging a whole fish (and therefore the minimum separation between the guard structure and the imaging device) may be determined by the following formula:

[0051] Where X is the length of the fish to be measured, and Y is the angle of the field of view of the imaging device. At this distance, a size of the guard structure may be approximately equal to or greater than X. For example, a circular guard structure positioned at a distance D may have a diameter of X or more. It will be understood that the guard structure may be placed further away from the imaging device than D, or that any other suitable means may be used to determine a suitable or desired separation distance between the guard structure and the imaging device.

[0052] The frame 102 may deter fish from approaching too closely to the image capturing device 101 , to thereby improve the rate of image frames capturing whole fish. Moreover, the increased size of the system 100 relative to the image capturing device 101 may increase a fish’s wariness of the system, to thereby reduce the likelihood of fish becoming stationary within the system’s field of view, or otherwise blocking the ability of the image capturing device 101 to capture images of other fish.

[0053] Figure 5 depicts a further example imaging system 500 according to the present disclosure. Similarly to system 100, the system 500 comprises an image capturing device 501 and a structure, cage or frame 502. The frame 502 in turn comprises an attachment structure 504, guard structure 506, and connecting bars 510. The discussions above regarding the functionality and optional or alternative features of the corresponding structures of system 100 apply equally to system 500.

[0054] Relative to cylindrical shape of frame 102, frame 502 is provided in a conical shape, with attachment structure 504 having a smaller radius than the guard structure 506. As would be understood by the skilled person, such a structure may be formed without restricting the field of view of the image capturing device 501 , as the field of view of an imaging system generally decreases in size as you approach the lens of the image capturing device. As such, the whole of frame 502, including attachment structure 504, guard structure 506, and connecting bars 510, may be provided outside of the field of view of the image capturing device 501. It will be understood that, as described with reference to system 100, the connecting bars 510 may be provided in addition to or replaced by netting or a solid connecting structure such as a housing or a cover. The attachment structure, guard structure and connecting structure may therefore form a hollow conical structure radially surrounding the field of view of the imaging device between the attachment structure and the guard structure.

[0055] In addition to the reduced weight and improved handling advantages that are provided by the smaller frame of system 500 relative to system 100, the conical design further enhances the stability of the guard structure 506 by providing attachment points (e.g. holes) for the connecting bars 510 on the attachment structure 504 that are in a different plane to the corresponding attachment points of the guard structure 506. In other words, the attachment points in the attachment and guard structures are positioned such that the connecting bars 510 are not parallel to one another, to thereby enhance the mechanical strength of the frame 502.

[0056] In the example system 500, attachment structure 504 is dimensioned to fit tightly to a case or housing of the image capturing device 501. However, it will be understood that the stability of the guard structure 506 may be enhanced as long as the dimensions of the attachment structure 502 are different to those of the guard structure 504. For example, where both the attachment structure 502 and the guard structure 504 are circular, the attachment structure 502 may have a diameter that is different to (i.e. smaller than or larger than) the diameter of the guard structure. Alternatively, the guard structure 504 and the attachment structure 502 may be different shapes, such that the connecting bare 510 are not parallel to one another.

[0057] It will be understood that corresponding advantages may likewise be provided by equivalent structures for other guard structure shapes. For example, if guard structure 506 is a square, the frame 502 may be pyramidal rather than conical.

[0058] Figures 6 and 7 respectively provide front and top views of the imaging system 500. Like reference numerals are provided in these figures.

[0059] Figure 8 depicts example dimensions of the system 500 in millimetres. A separation E between the image capturing device 501 and the guard structure 504 may be 390mm. At this distance, and for example, the guard structure 504 may have a diameter D of approximately 570mm. As discussed above, the dimensions of the frame 502 may vary based on several factors, and it will therefore be understood that these dimensions are provided as illustrative examples only, and are not intended to be limiting in nature.

[0060] It will be understood that the field of view of an image capturing device such as a camera may form various shapes, such as a viewing cone, a viewing pyramid, etc.

[0061] While implementations of the present disclosure are generally described with reference to a system for imaging and analysing (e.g. by performing welfare measurements) fish in a land or sea based fish farm, it will be understood that more generally any imaging system may benefit from the present disclosures. For example, imaging systems used in nature photography may likewise benefit from the addition of frame or guard structures for maintaining fish or other animals at at least a suitable minimum distance.

[0062] Figures 9A and B depict a schematic diagram of a further example system 900 according to the present disclosure. System 900 comprises a tank 902, such as a water tank configured to hold a body of water e.g. as part of a land-based fish farm. One or more walls or sides 904 of the fish tank comprises a viewing window 906. A frame 908 (such as frame 102 or 502) is then attached to the viewing window 906, such that an imaging device may be used to capture images of fish through the viewing window. It will be understood that the frame 908 may be connected or attached to an inside surface of the viewing window (e.g. via the attachment structure), such that the frame 908 is positioned in the body of water when in use. Alternatively, the frame 908 may be connected or attached to an outside surface of the viewing window (e.g. via the guard structure). In a further example implementation, the frame 908 may be attached to the wall or side of the tank 904 itself rather than the viewing window 906, such that frame 908 surrounds the viewing window 906.

[0063] The frame 908 may be attached to the tank 902 by any suitable means, e.g. removably attached to the tank 902 via any suitable means, such as screws, bolts, clamps, adhesive, etc. or it may be integrally formed as part of the tank 902. Optionally, the frame may be removably attached or connected to the tank 904.

[0064] Figures 10A and B depict further schematic views depicting example placements of a frame 1004 according to the present disclosure within a circular tank 1002, while Figures 11A depicts a schematic view of an example placement of the same frame 1004 within a rectangular tank 1102. Figure 11 B depicts an enhanced view of imaging system 1100 comprising an image capturing device such as a camera 1104 and viewing window 1106. As depicted in Figure 11 B, the frame 1004 may be attached to the tank 1002 / 1102 such that it is connected to the viewing window or such that it surrounds the viewing window.

[0065] Figures 12A and 12B depict an example frame or cage 1200 for an imaging system according to the present disclosure. Similarly to frame 102 depicted in Figure 1 , the frame 1200 comprises an attachment structure or ring 1204 configured to attach or connect the frame 1200 to an image capturing device, a guard structure or ring 1202 configured to maintain fish at at least a minimum distance from the image capturing device, and a plurality of connecting spokes or bars 1206 connecting the attachment structure 1204 and the guard structure 1202.

[0066] Additionally, the frame 1200 comprises a perforated cover 1208 such as a net or other mesh material arranged between the attachment structure 1204 and the guard structure 1202. The cover 1208 may be positioned externally around frame 1200 (e.g. on an outer surface of bars 1206, as shown in Figures 12A and 12B) or internally (e.g. on an inner surface of bars 1206).

[0067] The cover 1208 may be attached to one, some or all of the attachment structure 1204, the guard structure 1202, and one or more of the connection bars 1206.

[0068] The cover 1208 may surround part or all of the perimeter of the frame 1200. Advantageously, the perforations of the cover 1208 may be sufficiently small to prevent the ingress of smaller fish between the bars 1206 of the frame 1200, while still allowing a flow of water through the frame.

[0069] While Figures 12A and B depict an example cylindrical frame 1200, it will be understood that a perforated cover may be provided in conjunction with any implementations of frames or cages according to the present disclosure, including but not limited to cylindrical frames, conical frames, pyramidal frames, or any other desired frame shape.

[0070] The skilled person will understand that in the preceding description and appended claims, positional terms such as ‘front’, ‘top’, etc. are made with reference to conceptual illustrations of an apparatus, such as those showing standard perspective views and those shown in the appended drawings. These terms are used for ease of reference but are not intended to be of limiting nature. These terms are therefore to be understood as referring to a device when in an orientation as shown in the accompanying drawings.

[0071] Although the disclosure has been described in terms of preferred embodiments as set forth above, it should be understood that these embodiments are illustrative only and that the claims are not limited to those embodiments. Those skilled in the art will be able to make modifications and alternatives in view of the disclosure, which are contemplated as falling within the scope of the appended claims. Each feature disclosed or illustrated in the present specification may be incorporated in the disclosure, whether alone or in any appropriate combination with any other feature disclosed or illustrated herein.

Claims

CLAIMS:

1. A system for capturing images of one or more fish, the system comprising: an optical imaging device configured to capture images of the one or more fish; and a guard structure attached to the optical imaging device, wherein the guard structure is positioned outside of a field of view of the optical imaging device such that the guard structure at least partially surrounds the field of view of the optical imaging device; and wherein the guard structure is separated from the optical imaging device such that the field of view of the optical imaging device at the guard structure is larger than a size of the one or more fish to be imaged.

2. The system of claim 1 , comprising an attachment structure for attaching the guard structure to the optical imaging device.

3. The system of claim 2, comprising one or more connecting structures extending between the guard structure and the attachment structure.

4. The system of claim 3, wherein the one or more connecting structures comprise a plurality of connecting bars, and wherein the plurality of connecting bars are not parallel to one another.

5. The system of claim 4, wherein the guard structure and the attachment structure are the same shape, and the attachment structure is smaller than the guard structure.

6. The system of claim 4, wherein a separation between adjacent connecting bars of the plurality of connecting bars is greater than a size of the fish to be imaged.

7. The system of claim 4, wherein one or more of the plurality of connecting bars are removably attached to the guard structure and the attachment structure.

8. The system of claim 4, wherein the one or more connecting structures, the guard structure and the attachment structure form a cylindrical shape.

9. The system of claim 4, wherein the one or more connecting structures, the guard structure and the attachment structure form a conical shape.

10. The system of claim 1 , wherein the guard structure is a circle or an oval.

11. The system of claim 2, wherein the attachment structure is removably attached to the optical imaging device.

12. The system of claim 2, comprising netting between the guard structure and the attachment structure.

13. The system of claim 1 , wherein the guard structure is red, orange or yellow.

14. The system of claim 1 , wherein the guard structure comprises a material denser than water, optionally wherein the guard structure comprises metal.

15. The system of claim 1 , wherein the system is configured to perform welfare measurements of the one or more fish based on the captured images, optionally wherein the welfare measurements comprise at least one of biomass measurements, size measurements, and wound detection.

16. The system of claim 1 , wherein the optical imaging device is a stereoscopic camera.

17. The system of claim 1 , comprising a perforated cover positioned between the guard structure and the optical imaging device.

18. A guard structure for an underwater optical imaging device, the guard structure configured in use to be positioned outside of a field of view of the optical imaging device such that the guard structure at least partially surrounds the field of view of the optical imaging device; and wherein the guard structure is configured in use to be separated from the optical imaging device such that the field of view of the optical imaging device at the guard frame is larger than a size of the one or more fish to be imaged.

19. The guard structure of claim 18, comprising an attachment structure for attaching the guard structure to an underwater optical imaging device and one or more connecting structures extending between the guard structure and the attachment structure.

20. A system comprising: a tank for holding a body of water with one or more fish; a viewing window in the tank; anda guard structure for an underwater optical imaging device connected to or around the viewing window, the guard structure configured in use to be positioned outside of a field of view of the optical imaging device such that the guard structure at least partially surrounds the field of view of the optical imaging device; and wherein the guard structure is configured in use to be separated from the optical imaging device such that the field of view of the optical imaging device at the guard frame is larger than a size of the one or more fish to be imaged.

Images