Aquatic animal management apparatus and method

Abstract

An aquaculture system, flow-through partial use and particularly a recirculating aquaculture system, for grading and harvesting aquatic species on a continuous basis. The apparatus has a tank (1) for farming the species and a fixed, apertured screen (7) and a movable apertured screen (8a, 8b) adapted to sweep through the water towards or away from the fixed screen, defining two or more enclosures of variable size in which the aquatic species may be corralled based on their size. The apparatus provides a means of utilising the full volume of the tank continuously thereby improving efficiency, utilisation and improving welfare of the farmed species.

Description

[0001] AQUATIC ANIMAL MANAGEMENT APPARATUS AND METHOD

[0002] This invention relates to an aquatic animal management apparatus and method, particularly to an apparatus and method for isolating grading and harvesting aquatic animals, especially fin fish and crustaceans.

[0003] Aquaculture or aquafarming is a controlled process of cultivating aquatic species, for example, fish, crustaceans and shellfish, and may also be used for a variety of purposes including managing habitat and in regeneration of wild populations of aquatic organisms. Aquaculture may be carried out in a range of salt water, fresh and brackish water environments depending on the organisms under cultivation. Large-scale tanks, typically circular in cross-section, are commonly employed and find extensive use in the commercial production of fish and other aquatic organisms for the food sector. As the human population continues to grow rapidly and demand for sustainable, environmentally friendly, high quality protein grows accordingly, the demand for fish, crustaceans and other organisms produced by aquaculture is expected to grow markedly in the coming years, creating increasing demand for farmed fish, crustaceans and the like.

[0004] Conventional aquaculture systems may be of the recirculating type in which water inflow and outflow is retained within a closed system, flow-through type in which water is generally used once; net pen aquaculture systems are located within in a body of water, for example a loch, lake or sea environment, and are open to the environmental conditions, floating closed containment systems are also known wherein water from the body of water is brought into the aquaculture system and discharged from the system back into the external body of water. Partial flow-through or re-use aquaculture systems in which a higher percentage of water is discharged and the remaining water is treated and reused are also known. Recirculating aquaculture systems typically involve provision of large-scale water tanks equipped with filtration, internally or externally to recirculate and to treat the water for reuse and careful control of water conditions to optimise growth of the aquatic organisms. Water enters the tank through an inlet, and exits the tank via a drain to then be treated and recirculated to the tank.

[0005] Fish swim-speed, water velocity, oxygen levels, water residence time, removal of waste such as biosolids, CO2 and maintenance of appropriate water quality are important factors to control and inter-related. The rate and method of inflow and outflow of water to the system determines the flow distribution of the body of water in the tank and aims to promote uniform mixing, delivery of oxygenated water and rapid removal of biosolids. Flow velocities within the tank also must be controlled to enable an optimal fish swimming-speed. Where the fish's swimming-speed is too low, the fish may develop fat, be under-exercised, adversely affecting the quality and welfare of the fish thus reducing system efficiency. Where fish swimming-speed is too high, the fish require greater levels of food to provide additional energy, raising costs and impairing the quality of the fish which may result in fatigue, liver damage, skin lesions, increased blood cortisol, aggressive behaviour and competition for lower velocity water. Flow velocities therefore need to be controlled within certain limits to ensure appropriate swimming-speeds.

[0006] A larger tank generally requires a higher flow velocity to maintain a given level of oxygenation and rate of waste removal. This generally imposes an upper limit on size of tank in a recirculating system, typically around 30m diameter and 10m deep due to the need to avoid the flow velocity being too high for the optimal swim-speed of the aquatic organisms. This in turn sets an upper limit for the yield of aquatic organisms per volume of tank and hence the economic return.

[0007] Mixed-cell raceways are known which combine aspects of linear raceways and circular tanks to overcome drawbacks of linear raceways, for example high rates of reuse with risk of disease transmission and increased mortality.

[0008] As the aquatic species grow in a tank, they must be managed and graded, typically by size, and ultimately, harvested. Currently, aquatic animals are moved from one location to another using a number of different methods including manually using nets or ridged screens to corral the animals which typically involves the animal leaving the water, and fish pumps that either utilise a hydro cyclone and hoses, or screws within a pipe. While these methods are effective, they can cause damage and injuries to sensitive species for example crustaceans, fry and harvest ready animals). As well as stress and potential harm to the animals, such drawbacks may also result in loss of stock and attendant economic benefit loss and are labour intensive.

[0009] Furthermore, the size of tank required for young stock and for fully grown stock are very different. The tank may thus be oversized for early stage stock and only become fully efficient as the population approaches the target weight for harvesting. Management of the population to grade stock and to retain appropriate stock levels according to the tank size and operating conditions is complex and labour intensive. We have now found that the disadvantages of grading including handling the species, removal of the species from the tank, use of pumps and the like, and harvesting and other means of grading and harvesting aquatic animals may be reduced or overcome by providing a tank or containment having several screens mounted in the containment and configured to provide multiple enclosures having a variable and adjustable volume within the containment.

[0010] In a first aspect, the invention provides an aquaculture system for supporting aquatic species comprising: a containment comprising a side wall and a floor defining a containment zone for retaining a body of water to provide habitat for the aquatic species; at least one inlet for receiving water into the containment; at least one drain for removing solid waste from the aquatic species; at least one outlet for removing water and optionally waste from the containment; a fixed vertical screen comprising apertures to permit water flow therethrough and to prevent passage through the apertures of the fixed screen of aquatic species in the containment above a defined size; at least one movable screen movable relative to the fixed screen and comprising apertures to permit water flow and to prevent passage through the apertures of the movable screen of aquatic species in the containment above a defined size.

[0011] The terms “tank” and “containment” are employed interchangeably herein to mean the same thing.

[0012] The drain and the outlet may be provided by a single assembly whereby water, waste such as food and fatalities, are removed in a single assembly or may be provided as separate assemblies with water being removed from the outlet, optionally with waste and a solid waste, such as faeces and mortalities being removed from the drain. The drain is suitably located on the floor of the containment whereby solid waste falls under gravity to the drain for removal from the containment. The outlet may be located at any place in the containment and is preferably located in or at the top of the wall defining the containment.

[0013] The system and apparatus provides a means of grading and harvesting aquatic species without removing the aquatic species from the tank or containment. The species may be graded in a continuous and noon-invasive manner, that is, without manual or automated handling to remove the species to another location. The invention enables dynamic grading by allowing the aquatic species to be graded based on size using at least one circumferentially movable screen. The grading and harvesting may be carried out based on size and grading and harvesting is carried out within the containment by corralling the species into an enclosure so as to reduce stress, harm or damage to the species.

[0014] In a preferred embodiment, the containment does not contain any circumferentially extending barrier between the centre of the containment and the peripheral wall of the containment. The aquatic species accordingly are provided with a full radial dimension of the containment at different points of which the rotational velocity of the water is different. This allows the aquatic species to find the appropriate radial location depending on the species and size and swim speed of the species.

[0015] Advantageously, the invention provides apparatus in which a plurality of enclosures are defined within the containment and the size of the enclosures and be altered. Access to the enclosures may be controlled by selection of the size of apertures in screens defining the enclosures, enabling selection or corralling of a subset of the aquatic species based on their size and retention of the subset within an enclosure, separately of other species of different size in the containment. This is also advantageous when feeding as different sized animals required different sized feeds, thus further increasing efficiency.

[0016] Once corralled, the proportion of the species within the containment of the desired size may then be removed without interference with the remaining species in the containment. The apparatus accordingly provides a means of selectively grouping the animal species during the residence time of the species in the containment at any point in time.

[0017] The invention is suitable for grading and harvesting finned fish, for example salmon, trout and the like. Finned fish such as salmon may be graded into different weight bands and each weight band corralled and isolated from fish of different weights. Suitable weight bands will differ from species to species of fish. Suitable weight bands for salmon include 0.15 to 3g; 3 to 20g; 20 to 50g; 50 to 70g; 70 to 160g; 160 to 350g; and 350g or larger are suitable for harvesting.

[0018] The invention is also suitable for grading and harvesting crustaceans, for example prawns and shrimps. The term “grading” refers to selectively separating subsets of the aquatic species into distinct groups in separate enclosures based on size or mass, which is reflective of the growth and age of the species, such that the different size animals in each group can no longer inter-mix. For example, shrimps of mass 1g may be stocked within the containment in an enclosure defined between two screens. The two screens define two enclosures within the containment and movement of the movable screen allows the relative size of the enclosures to be changed as required and as the animals grow, thereby increasing the size of the enclosure such that the space in the enclosure is adequate for the health and well-being of the animals therein. Animals which are smaller than the desired size for corralling are suitably permitted to pass through the screen into the other enclosure(s)

[0019] Once the shrimps are at a mass of 5 to 8g a movable screen may be removed from the containment or the apertures increased in size to allow the shrimp access to another enclosure within the containment. The other containment suitably includes one or more screens with apertures of a size to restrict the passage of the shrimps through that screen. This process suitably continues as the shrimp grow until they are at a suitable size for harvest. Further small shrimp may be added to the containment, for example every 30 days, as and when necessary to provide full utilisation of the volume of the containment. In a preferred embodiment, the containment comprises 3 or more screens with suitably sized apertures to accommodate 3 or more batches of different sized shrimp.

[0020] Within 100 days of stocking a containment, shrimps may grow to 5g by Day 50 ie 50 days after stocking and then, in the period from Day 50 to Day 100, grow to 25g, with the greatest growth typically being from Day 90 to Day 100.

[0021] Typically, large, “final size” animals will require a much larger containment than for early- stage animals of a given species. The present invention enables species of all sizes from stocking to “final size” to be held within the same containment by providing separate enclosures with access to the enclosures being controlled based on the size or mass of the animals. The containment may accordingly be continuously restocked and “final size” animals removed as they reach full size, thereby providing a continuous farming method, rather than having to remove all animals from a containment for separation into different sizes or having to remove animals manually from a containment.

[0022] Once the animals of the desired size have been corralled, they may then be removed from the containment, for example by moving the animals to a new zone, separate from the containment by opening an access path from the containment to the new zone whereby the animals migrate to the new zone.

[0023] The invention allows for continuous production to take place in a single containment or set of containments, improving productivity relative to conventional methods which typically involve ‘batch in / batch out’ in which the containment is only at capacity at the end of the growing cycle. For example, penaeids, that is prawns and shrimps typically has a growing cycle of 90 to 120 days, whereby, in conventional apparatus, 3 to 4 life cycles per year may be possible, where the full-size shrimp are removed from the containment and new stock are introduced for the next cycle. The invention enables continuous replenishment of the species and enables more stocking cycles to be accommodated in a given period, for example up to 9 to 12 cycles for penaeids. This improves efficiency and utilisation of the apparatus.

[0024] For fin-fish, swim speed is an important consideration and smaller and larger animals of a species have different swim speeds. The invention enables fish to be separated or graded on a continuous basis and farmed in different containments in which the local conditions may be selected according to the optimal requirements of the animals at that stage in their growth.

[0025] The apparatus may be used to provide a method of continuously grading the animal species rather than having to remove the species as a batch at periodic points in the residence time of the species, which, undesirably catches species of a wider size range than achievable with the present invention.

[0026] In a further aspect, the invention provides a method of farming aquatic animals in an aquaculture system according to the invention comprising: a. Stocking a population of young animals in the containment; b. After a first period, selected a subset of the population of animals according to the size of the animals by positioning the at least one movable screen to define with the fixed screen, at least two enclosures, permitting passage of the animals through the fixed and / or movable screen into an enclosure to provide a larger sized subset of the population in one enclosure and a smaller-sized subset in another enclosure; c. Stocking a further population of young animals in the containment; and d. Optionally removing the larger subset of animals from the containment.

[0027] In a preferred embodiment, at least one movable screen is moved from about an axis at or near the centre of the containment to sweep a portion of the containment so as to change the central angle between the fixed screen and the movable screen or between two movable screens.

[0028] The at least one movable screen is suitably moved by rotation about an axis at or near the centre of the containment. The screen is moved in a circumferential locus such that it sweeps a sector of a circle defined by the containment. Where there are two or more movable screens, suitably, they are independently movable. The two or more screens may be moved together or at different times to create a volume within the containment or to increase or diminish the size of a volume according to operational requirements.

[0029] The fixed screen and at least one movable screen may be located next to each other such that the containment has a single volume for the aquatic species. Where the at least one movable screen and fixed screen are spaced apart, they define, together with the wall of the containment two or more volumes sectors.

[0030] Suitably, the movable screen extends from at least the centre of the containment to the periphery so the aquatic species cannot pass around the extremities of the screen. The screen is suitably of a vertical dimension that the lower edge of the screen is at or near the bottom of the containment or may comprise a skirt from the bottom of the screen to the floor of the containment. The upper edge of the containment is suitably at or near the intended level of the surface of the water held in the containment.

[0031] The containment may comprise one or more outlet ports adapted to receive aquatic species as and when they are to be harvested from the system. The fixed screen and at least one movable screen are configured to ensure the volume of the containment with the largest aquatic species aligns with the outlet port such that aquatic species in the sector may pass through the port upon it opening.

[0032] The method provides a means of continuously grading the population of animals and continuously harvesting a proportion of the population of animals. As employed herein, the term “continuously harvesting” means removing a proportion of the population of animals in the containment when they reach a pre-determined “harvest-size” for the species while another proportion of the population of animals in the containment remain in the containment to continue their growth and, optionally, new young animals are introduced to the containment.

[0033] Selection of the animals for grading and / or harvesting based on size may be based on the dimensions of the animal or its mass.

[0034] The containment comprises a fixed vertical screen comprising apertures to permit water flow and to prevent passage through the apertures of the fixed screen of aquatic species in the containment above a defined size. The fixed screen suitably extends radially across the containment from the centre to the periphery. Below a pre-determined size, the aquatic species may pass through the apertures in the fixed screen. As the aquatic species grow and reach a certain size, the fixed screen presents a barrier to impede or deter and suitably prevent passage of the species through the fixed barrier.

[0035] The containment further comprises at least one movable screen which may be moved towards or away from the fixed screen. Suitably, the at least one movable screen is movable in a circumferential direction through the containment. The at least one movable screen is suitably movable about an axis of rotation at or near the centre of the containment. In a circular or near-circular containment, the mat least one movable screen suitably extends across the full radius of the containment, thereby to present a barrier to the aquatic species and, as the screen moves in a circumferential locus, corrals the aquatic species into a volume of changing size, for example the volume may be ahead of the sweep of the movable screen and diminish in size as the screen moves.

[0036] The movable screen comprises apertures to permit water flow and to prevent passage through the apertures of the movable screen of aquatic species in the containment above a defined size. At least one movable screen may be removed entirely from the containment if desired.

[0037] In a preferred aspect, the invention provides an aquaculture system for supporting aquatic species comprising: a containment comprising a side wall and a floor defining a containment zone for retaining a body of water to provide habitat for the aquatic species; at least one inlet for receiving water into the containment; at least one drain for removing solid waste from the aquatic species; at least one outlet for removing waste and water from the containment; a fixed vertical screen comprising apertures to permit water flow therethrough and to prevent passage through the apertures of the fixed screen of aquatic species in the containment above a defined size; at least two movable screens movable relative to the fixed screen, each movable screen comprising apertures to permit water flow and to prevent passage through the apertures of the movable screen of aquatic species in the containment above a defined size.

[0038] The at least one movable screen is suitably mounted such that it extends radially across the containment. The at least one movable screen is suitably mounted for rotation about an axis at or near the centre of the containment. Preferably the axis of rotation of the at least one movable screen is coincident with the end fixed screen at or near the centre of the containment. The at least one movable screen may be of a length “r” where “r” is the radius of the containment or may be of length “2r” and be mountable about the centre of the containment such that it defines two radial screens in fixed relationship, for example with an angle of 90 to 180° between the two parts, whereby both parts of the screen of length 2r are movable relative to the fixed screen but fixed relative to each other.

[0039] The fixed screen and at least one movable screen act together to define one or more enclosures within the containment. One or more of the movable screens may be moved towards or away from another movable screen or the fixed screen to alter the size of the enclosure defined by the screens. The movable screens may be moved so as to be adjacent to another screen to remove an enclosure. For example, in an embodiment with two movable screens, the two movable screens may be apart whereby they, together with the fixed screen define three enclosure. Moving one of the movable screens to be adjacent to the other movable screen or adjacent to the fixed screen provides a containment with two enclosures or, if the movable screens are both moved to be adjacent to the fixed screen, one enclosure, being the full volume of the containment.

[0040] The size of the apertures in any one or more fixed or movable screens may be varied by providing a mechanism to alter the aperture size in a screen and / or by placing two or more screens in an adjacent configuration such that the apertures in each of the adjacent screens are offset whereby the adjacent screens, together define a smaller aperture than any of the adjacent screens individually.

[0041] The fixed screen and at least one movable screen allow a containment to be divided into discrete enclosures whereby stock of different sizes may be segregated

[0042] Suitably the fixed screen and the at least one movable screen comprises an array of vertical bars and horizontal bars with the spacings defined by the bars and their intersection defining the apertures in the screen.

[0043] In a preferred embodiment, the vertical bars have a horizontal cross section which is teardrop shaped and is disposed such that the larger end of the tear drop faces towards the oncoming flow of water in the containment. Suitably, the teardrop cross section has a length of 20 to 100mm, preferably 30 to 75mm, for example 50mm. Suitably, the teardrop cross section has a width of 3 to 20mm, preferably 5 to 15mm, for example 10mm. In a preferred embodiment, the horizontal bars have a vertical cross section which is teardrop shaped and is disposed such that the larger end of the tear drop faces towards the oncoming flow of water in the containment. Suitably, the teardrop cross section horizontal bar has a length of 10 to 50mm, preferably 20 to 40mm, for example 25mm. Suitably, the teardrop cross section of the has a width of 2 to 12mm, preferably 3 to 8mm, for example 5mm.

[0044] In a preferred configuration, the horizontal bars are provided in pairs with a vertical spacing between each bar of the pair being 5 to 50mm, preferably 8 to 30mm, for example 10mm and 20mm. Suitably adjacent pairs of bars are spaced apart by 200mm to 1000mm, preferably 300 to 600mm, for example 400m and 500mm. Preferably, the lowest horizontal bar is from 5 to 50mm, preferably 10 to 30mm for example 20mm above the highest point of the floor of the containment.

[0045] If desired, one or more horizontal bars may be at an inclined angle, especially where the floor of the containment is sloping. Suitably, the bottom bar is parallel to the floor of the containment.

[0046] The apertures in different screens may be disposed such that as the screens are placed adjacent to each other the apertures in the adjacent screens are offset, thereby defining smaller apertures than in either of the adjacent screens.

[0047] Suitably one or more of the screens is configured such that the size of the apertures in the screen may be varied or opened such as to allow passage through the screen if the aquatic animals.

[0048] The body of water in the containment is suitably rotatable, suitably by impetus created by the directional inflow of water to the containment. The drain is suitably located in the floor of the containment at the intended axis of rotation of the body of water, typically towards and preferably at the centre of the containment.

[0049] Suitably, the drain allows solids together with some water to be removed from the containment. The water may be treated or processed to remove solids and other undesirable components and be recycled to the containment, optionally after further treatment for example to include food, nutrients or other desirable materials for treating or feeding the animal species. Suitably, the solids are removed from the system and, preferably, do not come into contact with the water for recycling to reduce the risk of contamination or inadvertently recycling unwanted solids.

[0050] The inlet for feeding water into the containment may be of any arrangement but suitably comprises one or more nozzles. The term “nozzle” is employed herein to refer to any means defining an aperture or inlet for water to pass into the containment, suitably in a controllable direction providing impetus to rotate the body of water in the containment.

[0051] The nozzle(s) are suitably located within the containment and oriented to provide water in flow in a direction which will rotate the body of water. Preferably the inlet is oriented such that water is directed in a tangential or circumferential direction relative to the containment. The inlet may comprise a plurality of nozzles located at or near the containment wall and aligned to provide a flow of water in a circumferential direction thereby to impart force to rotate the body of water in the containment.

[0052] In a preferred arrangement, the inlet comprises a plurality of nozzles aligned in a horizontal array and / or comprises a plurality of nozzles arranged in a vertical array. Suitably, the nozzles extend from a vertical axis and are orthogonal to each other. The inlet preferably comprises at least 3 nozzles wherein the nozzles are independently arranged at an angle of 0 to 45° relative to the containment wall adjacent to the nozzle. Preferably, adjacent nozzles are arranged at an angle of 90 to 22.5 degrees in the horizontal, relative to adjacent nozzles, when viewed in a vertical direction.

[0053] Suitably the floor of the containment comprises a plurality of vanes which aid water flow and direction and in directing waste, uneaten feed and other solids towards the centre of the containment and the drain. Rotational speeds of water in shrimp systems are suitably lower than for finned fish and vanes are especially useful in directing solids movement and mixing of water in slower speed systems. Preferably the vanes comprise a vertical solid plate having a length (parallel to the floor of the containment) to width (in the vertical dimension) of 10:1 to 2:1 , more preferably 5:1 to 3:1. Suitably the vane length is 1000 to 5000mm, preferably 1500 to 3000mm, for example 2000m. Suitably the vane width is 100 to 1000mm, preferably 500 to 800mm, for example 600mm. The depth of the vane is suitably 50 to 200mm, for example 100mm. The vanes are suitably located in the outer periphery of the floor of the containment. Where the containment has a radius “r”, suitably, the vanes are located between 3r / 4 and r from the centre of the containment.

[0054] The vanes are suitably aligned orthogonally to the direction of flow of water at the inlet or in a line from the direction of water at the nozzle to aid water flow in a circular locus within the containment. Preferably the vanes are at an angle under 45°, more preferably from 10 to 30°, for example 20° relative to the predominant direction of water flow at the inlet.

[0055] Optionally, the containment may further comprise an air inlet port and an air outlet port.

[0056] Suitably, the drain receives not more than 30%, preferably not more than 20%, more preferably 2 to 10% of the water flow within the containment. The larger solids which are removed from the containment via the drain suitably comprises at least 80%, preferably at least 90%, especially at least 95%, for example more than 99% of the total solids waste being removed via the drain and a minor proportion of the material total being water.

[0057] Suitably, the containment may be any suitable shape which permits efficient rotation of a body of water in the containment. Preferably, the containment is circular, polygonal, part circular or part polygonal shape, preferably octagonal, dodecagonal or hexadecagon. The containment suitably is operably connected to means for supply to the containment of water and optionally other components, for example oxygen, nutrients and the like and for removal of water, waste and optionally other components from the containment via the drain and optionally a water outlet .The floor of the containment may be level or comprise areas or the whole of the floor sloping radially downwards from the periphery towards a low point in the middle area, for example the centre, whereby solids. Particularly mortalities are settled at the bottom and are urged under gravity and the centripetal force generated by the rotating water to the drain for removal.

[0058] In another embodiment, the containment may comprise multiple cells, for example as described in pending application PCT / EP2022 / 078392. In one embodiment, the containment comprises a plurality of cells, preferably 4 cells, defined within the containment, each cell being configured to hold a body of water which is rotatable within the cell, each cell being in fluid communication with at least one other adjacent cell. The containment suitably has at least one inlet for receiving water into each cell configured to allow the body of water in that cell to be rotatable. Where the containment comprises multiple cells or zones, each with its own body of rotatable water, a drain is suitably located in each zone so as to provide a means of removing unwanted solids from each zone.

[0059] Where the containment comprises a plurality of cells, suitably, the containment comprises a base, a peripheral side wall and internal walls located so as to define the plurality of cells within the containment. Preferably each cell is shaped such that a body of water in the cell is rotatable within the cell, the cell being defined by internal walls, optionally a portion of the peripheral wall and at least one space in the walls to enable fluid communication with an adjacent cell. Each cell is defined by a portion of the peripheral wall, with at least two internal walls extending from the peripheral wall towards the inner area of the containment, and a further wall which extends to the two internal walls with a space between the further wall and the internal walls.

[0060] Preferably, the further wall for each cell is provided by an adjacent tank or preferably a structure comprising a water outlet. The structure is suitably located between two or more cells and, preferably is located generally in the centre of the containment. The structure suitably comprises a conduit for the supply of water to each of the inlets, preferably an inlet in each cell. The inlet may comprise one or more nozzles, preferably 2 to 10 nozzles, for example 6 nozzles for a 7m containment and suitably, the number of nozzles is selected according to the size of the containment. The inflow of water through the inlets imparts force to the body of water within the cell and thereby rotates the body of water within that cell. The structure suitably provides an outlet for water and a drain as described herein in each of the cells and may also provide a means of ingress and egress of other materials.

[0061] Preferably, the structure is configured to enable outflow of water from the containment. In a preferred embodiment, the structure comprises a weir enabling outflow of water from each cell. Suitably, the weir is at height such that of the outflowing water in the containment, at least 50%, preferably at least 80%, especially at least 95% of the water is removed from the containment via the weir. The balance of the water is suitably removed from the containment via the drain. Optionally, the structure comprises means of feeding a component to and / or removing a component from the system / , for example oxygen, nutrients and the like.

[0062] In a preferred embodiment, the outlet comprises a dam to permit flow of water from the cells into the structure comprising the water outlet. In a preferred embodiment, the structure is located centrally in the containment with the cells arranged around the structure such that water may flow from each cell into the structure via a weir. Preferably, the plurality of cells are disposed in a close-packed or tessellated arrangement relative to each other. In an alternative embodiment, the plurality of cells are disposed longitudinally. More preferably, the containment comprises 4 cells wherein the cells are arranged such that the cells are in a generally square arrangement. Suitably, each cell’s peripheral wall is generally of constant radius whereby the containment has a generally quatrefoil shape.

[0063] Suitably, the inlet for each cell is located so as to enable rotation of the body of water in that cell at a rate and direction substantially independently of the rate and direction of the body of water in the other cells. Suitably, the inlet comprises a plurality of nozzles or other means defining an aperture to allow passage of water therethrough into the cell, for example slots.

[0064] Suitably, less than 10%, preferably less than 5%, more preferably less than 1%, particularly not more than 0.2% and, especially minimal mixing occurs between the body of water within one cell with that of an adjacent cell, the percentage being based on the volume of water within one cell. For example, in a containment of 35 to 40m diameter comprising four cells arranged in a square, with the cells being generally circular or of regular polygon shape such that the cells are of the order of 17.5 to 20m diameter and approximately 5m deep, the fluid pathways between adjacent cells and the rate of rotation of the body of water in the cells is such that suitably less than 0.5% mixing occurs, for example less than 2000 litres per minute of water mixes between adjacent cells with a cell volume of 2 million litres.

[0065] The water within a cell suitably remains substantially within that cell and is rotatable in the opposite direction to the body of water in an adjacent cell. The residence time of a body of water in a cell is influenced by the size of the cell. Suitably, for a cell of 2 to 4m diameter or maximum dimension of 4 to 8m the residence time of the body of water in the cell is of the order of 12 to 20 minutes, larger cells, for example a cell of 12 to 20m diameter may have a residence time of 30 to 60 mins. For even larger cells, greater than 20m diameter, 30 to 40m, a residence time of the order of 80 to120 minutes may be optimal. The maximum swim speed suitable for the organisms being farmed will determine the maximum rate of rotation and inflow of water which determines the residence time for a given tank size and optimal swim-speed. These factors are suitably selected having regard to the type of organisms being farmed, the stocking density of the organisms, the size of the fish and their optimal swim speed to ensure appropriate fish welfare and quality. Where the aquaculture system is employed for farming crustaceans, the swim-speed may be a less significant factor than when farming fish, allowing larger containment sizes, for example a containment of 100m diameter may be employed with a residence time of 2 to 3 hours.

[0066] The containment also comprises a water outlet which may be in the form of a weir or a conduit in the wall or floor of the containment or, where the containment comprises multiple cells, in the form of a central outlet with a weir such that water is removed from the containment at or near the surface of the water rather than at or near the floor of the containment. Suitably, the cells are configured in an arrangement to enable the water outlet to receive water from at least two and preferably all the cells at a location adjacent to two or more cells. The water outlet may be located at a boundary of two or more cells. Suitably, the cells and water outlet are configured such that the water outlet is generally centrally located between the plurality of cells.

[0067] The aquaculture system and method of the invention may be employed as a recirculating system, a flow-through system and as a partial flow-through system. In a recirculating system and a partial flow-through system, a treated aqueous stream is suitably delivered to the containment.

[0068] In a recirculating system, the body of water is constantly recycled within the system which is generally closed, although excess water may be removed from the system or water from outside the system be fed to the system as required; suitably such additional water is less than 10% of the volume of water in the containment, preferably less than 5% and especially less than 1% by volume per day. An aquaculture system according to the invention suitably comprises a conduit for recirculating water from the at least one outlet and drain to the at least one inlet. Water which is recirculated in the system of the invention is suitably treated for example to remove waste, to replenish with oxygen, nutrients or the like, or subjected to disinfection such as UV irradiation and ozone disinfection.

[0069] In a flow-through system according to the invention, the system is suitably adapted to be located within a natural body of water, for example the sea or a lake, in which water inflow from the surrounding external body of water and outflow to the body of water is pumped under controlled conditions. Water is received from an external body of water, resides within the aquaculture system for a period of time and then discharged from the system back into the external body of water, preferably the majority of solids are captured and removed for disposal via a drain as defined herein. In one embodiment of a flow-through system according to the invention, where the containment is land based it may comprise at least in part a filter enabling passage of water between the volume contained by the containment, and the external body of water. The filter may act as the inlet for water from the external body into the containment and also act as the outlet for water from the containment to the external body of water.

[0070] The invention provides an aquaculture system according to the invention wherein the containment has one and preferably two orthogonal dimensions of at least 1m, preferably at least 5m, more preferably at least 7m. The containment is suitably not more than about 75m maximum dimension, preferably not more than about 50 to 60m. Preferably, the containment has a minimum dimension from 3.5m to 20m, for example 7m and 40m. The system and method of the invention suitably enable the flow rate of water through the at least one inlet to be controlled such that the velocity of the rotatable water is from 1 to 3, preferably 1.5 to 2.5 and more preferably 1.8 to 2, times the body length of the aquatic organisms per second being cultured with the containment.

[0071] The invention is illustrated below with reference to the accompanying drawings in which:

[0072] Figure 1 shows a perspective view of an aquaculture system according to the invention;

[0073] Figure 2 shows a perspective view of part of the aquaculture system according to the invention as shown in Figure 1 defining 2 enclosures;

[0074] Figure 3 shows a plan view of part of the aquaculture system according to the invention as shown in Figure 1 ; and

[0075] Figure 4 shows a perspective view of part of a screen in an aquaculture system according to the invention.

[0076] A containment (1) according to the invention is should having a side wall (2) and a floor (3) which define a containment zone for holding aquatic species. Water is fed into the containment via inlet (4), for example a nozzle or series of nozzles at different heights in the side wall which is angled so as to impart rotational force to the body of water in the containment. A drain (5) is provided in the centre of the floor (3) for removing solid waste such as faeces, mortalities, uneaten food and the like via drain pipe 6. The drain is of diameter “d” and is suitably covered by a grid or gauze.

[0077] The containment has a fixed screen 7 and movable screens (8a, 8b) which are rotatable about an axis in the centre of the containment (1). Each screen (7, 8a, 8b) has apertures defined by vertical members and horizontal members which are spaced so as to prevent the aquatic species passing therethrough once they attain a certain size. The size of the apertures in each screen may be the same or different to the size of apertures in other screens whereby each screen acts to filter animals of a different size, enabling segregation of animals by size in different enclosures.

[0078] The movable screens (8a, 8b) and the fixed screen (7) define multiple enclosures in the containment. The volume of the enclosures may be altered to allow optimal space for the species enclosed within that volume. Smaller animals may pass through the screens and move freely until they reach a certain size whereupon they will be restricted by being unable to pass through the apertures of the screen. In this way, animals may be segregated by size into different groups allowing the single containment (1) to be used for managing animals of different sizes in different ways and providing full utilisation of the space within the containment.

[0079] Movable screens (8a, 8b) may be moved relative to each other as shown in Figure 2 to alter the size of the enclosures defined between them and between each of them and the fixed screen (7). The movable screens may be brought together to remove an enclosure and by configuring the apertures in each screen such that they are out of register, the apertures win adjacent screens may together define smaller apertures than in either screen when the screens are flush against each other.

[0080] Figure 3 show removable vanes 10 to aid directional guidance to the water flow.

[0081] Figure 4 shows vertical and horizontal members of the movable screens (8a, 8b) have a tear-drop shaped cross section with fatter edges (12, 15) and thinner edges (13, 16). The vertical and horizontal members of the fixed screen may have a rectangular shaped crosssection as the screen is fixed and so is not moved through the body of water although a teardrop shape cross section is preferred to facilitate water flow as the water rotates to minimise disruption to the flow of water.

Claims

AMENDED CLAIMS received by the International Bureau on 10 December 2024 (10.12.2024)1. An aquaculture system for supporting aquatic species comprising: a containment comprising a side wall and a floor defining a containment zone for retaining a body of water to provide habitat for the aquatic species; at least one inlet for receiving water into the containment; at least one drain for removing solid waste from the aquatic species; at least one outlet for removing water and optionally waste from the containment; a fixed vertical screen comprising apertures to permit water flow therethrough and to prevent passage through the apertures of the fixed screen of aquatic species in the containment above a defined size; at least one movable screen movable relative to the fixed screen and comprising apertures to permit water flow and to prevent passage through the apertures of the movable screen of aquatic species in the containment above a defined size wherein the containment does not contain a circumferentially extending barrier.

2. An aquaculture system for supporting aquatic species comprising: a containment comprising a side wall and a floor defining a containment zone for retaining a body of water to provide habitat for the aquatic species; at least one inlet for receiving water into the containment; at least one drain for removing solid waste from the aquatic species; at least one outlet for removing water and optionally waste from the containment; a fixed vertical screen comprising apertures to permit water flow therethrough and to prevent passage through the apertures of the fixed screen of aquatic species in the containment above a defined size; at least two movable screens movable relative to the fixed screen and comprising apertures to permit water flow and to prevent passage through the apertures of the movable screen of aquatic species in the containment above a defined size3. An aquaculture system according to claim 1 or claim 2 wherein the movable screen(s) are movable towards or away from the fixed screen to define one or more enclosures.

4. An aquaculture system according to any one of the preceding claims wherein the fixed screen is vertically mounted in the containment and extends radially across the containment from the centre to the periphery.

5. An aquaculture system according to any one of the preceding claims wherein the at least one movable screen is vertically mounted in the containment for horizontal rotation about an axis at or near the centre of the containment and extends radially across the containment.

6. An aquaculture system according to any one of the preceding claims wherein the at least one movable screen extends across the full radius of the containment to the wall of the containment and is adapted to sweep around the containment such that the fixed screen and at least one movable screen or two or more movable screens define a sector with a variable central angle between the two screens.

7. An aquaculture system according to any one of the preceding claims wherein the at least one movable screen, is of length “2r” where “r” is the radius of the containment and is mounted about the centre of the containment such that it defines two radial screens in fixed relationship to each other and movable relative to the fixed screen.

8. An aquaculture system according to any one of the preceding claims wherein the fixed screen and the at least one movable screen each comprise and array of vertical bars and horizontal bars9. An aquaculture system according to claim 8 wherein the horizontal bars are provided in multiple pairs of bars.

10. An aquaculture system according to claim 8 or claim 9 wherein the horizontal bars and vertical bars have a tear drop cross-section.

11. An aquaculture system according to any one of the preceding claims wherein the containment further comprises an air inlet port and optionally an air outlet port.

12. An aquaculture system according to any one of the preceding claims wherein the containment is circular, part circular, polygonal or part polygonal such that the body of water is rotatable in the containment.

13. An aquaculture system according to any one of the preceding claims comprising means to rotate the body of water in the containment.

14. An aquaculture system according to any one of the preceding claims wherein the drain is selectively openable.

15. An aquaculture system according to any one of the preceding claims wherein the drain is located at or near the centre of the containment.

16. An aquaculture system according to any one of the preceding claims wherein the drain comprises a filter to prevent passage of live species into the drain from the containment.

17. An aquaculture system according to any one of the preceding claims wherein the drain and outlet are provided in a single assembly.

18. An aquaculture system according to any one of claims 1 to 16 wherein the drain and outlet are provided separately with the drain being located at or near the centre of the containment and the outlet being located in the wall or at or near the top of the wall of the containment.

19. An aquaculture system according to any one of the preceding claims wherein the containment comprises a plurality of cells defined within the containment, each cell being configured to hold a body of water which is rotatable within the cell, each cell being in fluid communication with at least one other adjacent cell and each cell comprises a drain located in the centre of the cell.

20. An aquaculture system according to claim 19 wherein the containment comprises at least 3 cells.

21. An aquaculture system according to any one of claims 19 and 20 wherein each cell is defined by a portion of the containment wall, two internal walls extending from the containment wall towards the inner area of the containment, and a further wall which extends to the two internal walls with a space between the further wall and the internal walls.

22. An aquaculture system according to claim 21 wherein the further wall for each cell is provided by a structure located generally in the centre of the containment.

23. An aquaculture system according to claim 22 wherein the structure comprises a water outlet.

24. An aquaculture system according to claim 22 or 23 wherein the structure comprises a weir for the removal of water from each cell.

25. An aquaculture system according to any one of claims 19 to 24 comprising 4 cells wherein the cells are arranged such that the cells are in a generally square arrangement.

26. A method of farming aquatic animals in an aquaculture system according to any one of the preceding claims comprising: a. Stocking a population of young animals in the containment; b. After a first period, selecting a subset of the population of animals according to the size of the animals by positioning the at least one movable screen to define with the fixed screen, at least two enclosures, permitting passage of the animals through the fixed and / or movable screen into an enclosure to provide a larger sized subset of the population in one enclosure and a smaller-sized subset in another enclosure; c. Stocking a further population of young animals in the containment; and d. Optionally removing the larger subset of animals from the containment.

27. A method according to claim 26 in which at least one movable screen is moved from about an axis at or near the centre of the containment to sweep a portion of the containment so as to change the central angle between the fixed screen and the movable screen or between two movable screens.

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