WO2008032102A2

WO2008032102A2 - Artificial aquatic environment

Info

Publication number: WO2008032102A2
Application number: PCT/GB2007/003519
Authority: WO
Inventors: Alexander Paul Muhlholzl
Original assignee: Alexander Paul Muhlholzl
Priority date: 2006-09-15
Filing date: 2007-09-17
Publication date: 2008-03-20
Also published as: WO2008032102A3

Abstract

An aquaculture system for use in providing an artificial aquatic environment for accommodating an organism, including, for example, but not exclusively, a fish (24). The system comprises a vessel or tank (12) for holding a quantity of fluid such as water, the vessel defining a flow path. A current forming device (18) is utilised to move fluid along the flow path. The invention also relates to the use of one or more deflector (18) to exert a force on the organism to direct the organism (24) away from a wall '(14, 16) of the vessel in order to prevent or mitigate damage to the organism as a result of hitting the vessel wall.

Description

ARTIFICIAL AQUATIC ENVIRONMENT

FIELD OF THE INVENTION

The present invention relates to an aquaculture system for use in providing an artificial aquatic environment and, in particular, but not exclusively, to a tank for the rearing of fish.

BACKGROUND OF THE INVENTION

The impact of commercial fishery activities on wild populations of fish species is of significant environmental concern. Additionally, the costs associated with using traditional fishing methods to harvest fish stocks have increased with the depletion in the natural populations of fish species and with increases in labour costs.

As a result, various aquaculture systems have been developed to reduce the costs of production and limit the impact on the natural environment. These aquaculture systems have typically been directed towards the more lucrative salt water fauna and include systems such as, for example, tanks for abalone (a species of shellfish) and ocean situated netted cages for fish species such as tuna.

Difficulties associated with the use of tuna cages include that the system still requires the cage to be towed into the fishing grounds and the tuna to be caught and placed into the cage. Accordingly, it will be recognised that such a system still has an impact upon the natural populations and questions have been raised about its sustainability.

One particular difficulty arises in raising larval or juvenile fish in an artificial environment in order to stock fish farms. Standard tank designs are of an enclosed type, being, typically, round, square or rectangular in shape. When these tank designs are used for tuna in the "grow-out" stage, it has been found that the mortality rates of the fish can typically be as high as 95% and, in some cases, 100%.

It is thought that one reason for these high mortality rates is that larval or juvenile tuna have a large tail fin and small dorsal fins, this resulting in a fish that is poor at turning.

They also have a large muscle mass and a very high metabolism and can therefore attain significant speeds. Thus, due to their physiology and high metabolism, the fish often swim into the walls or side netting of pens at high speeds. This typically results in significant injury or death from impact damage such as broken necks. Furthermore, as a school fish, the tuna have a tendency to swim into a wall because only the first ranks of the school will see the wall or netting. In addition, it is known that species of fish such as tuna can be easily "spooked", that is where the fish display a natural flight response by swimming at speed in the current direction of travel. As a result, the fish regularly impact the sides of tanks and cages resulting in injury or death.

SUMMARY OF THE INVENTION According to a first aspect of the present invention, there is provided an aquaculture system for use in providing an artificial aquatic environment for accommodating an organism, the system comprising: a vessel adapted to hold a quantity of fluid therein, said vessel defining at least one flow path; and a current forming device adapted to induce movement of fluid along said flow path.

The organism may comprise a species of fish and, in particular, but not exclusively, the organism may comprise larval or juvenile fish. For example, but not exclusively, the organism may comprise a tuna.

The provision of a system according to the present invention may provide an artificial environment in which aquatic organisms such as tuna can be nurtured. The configuration of the vessel permits a flow path to be created which minimises the likelihood of, in particular, but not exclusively, larval or juvenile fish impacting the walls of the vessel thereby assisting in a reduction in injury or mortality rates caused by impact shock. Thus, where a flight response occurs, the fish will swim along the flow path rather than impacting the walls of the vessel.

The flow path may be continuous. For example, the flow path may comprise a loop.

The system may further comprise a deflector for assisting in directing the organism away from a wall of the vessel. The deflector may be adapted to exert a fluid force on the organism to assist in directing the organism away from the wall of the vessel. The deflector may be adapted to exert a fluid force at an angle to the flow path. The fluid force may be adapted to be exerted in line with the flow, or angled towards or against the flow. The deflector may comprise any suitable means, for example, but not exclusively, the deflector may comprise one or more fluid jet, for example, a water jet. The fluid jet may be adapted to exert a force on the organism. Furthermore, the fluid jet may be adapted to be angled to create a directional fluid current or flow to direct the organism away from the wall of the vessel. The fluid jet may be adapted to provide a force on the organism via the liquid current. For example, the fluid jet may provide a current which prevents, or mitigates, damage to the organism as a result of an impact of the organism with the vessel. Alternatively, or in addition, the presence of the fluid force may be sufficient to encourage the organism to stay away from the walls of the vessel. Thus, the use of one or more liquid jet may facilitate controlling the position of the organism in the vessel.

Furthermore, the fluid jet may alternatively or additionally be adapted to move sediment or waste to a desired location for removal and/or to introduce liquids or solids into the vessel, including for example, feed, anaesthetic or therapeutants.

Alternatively, the deflector may comprise a mechanical deflector such as for example, foam, netting or any other suitable means for deflecting the organism away from the wall of the vessel. It will be recognised that where a flight response is induced, the presence of a flow path encourages the organism to swim around the flow path rather than into the wall of the vessel. In addition, the provision of a deflector will prevent or at least mitigate damage to the organism if they approach the vessel wall by deflecting the organism away or by decelerating the organism prior to impact. It will be recognised that lower speeds of impact will be less damaging to the organism. The vessel may comprise a base, an outer wall and at least one side wall which define the flow path.

Where more than one side wall is provided, the side walls may be substantially parallel.

The vessel may have an elliptical, circular or athletics track shape configuration (that is, two liner sections bounded by two elliptical or circular ends). Alternatively, the vessel may be linear in shape. For example, the vessel may be adapted to define a straight channel with liquid entering from one end of the vessel and exiting out the other end of the vessel. However, it will be understood that the vessel may define any desired shape or configuration as required. The vessel may be constructed from any suitable material and may, for example, but not exclusively, comprise reinforced fibreglass, glass fibre reinforced plastic (GFRP) or other suitable material.

The vessel may further comprise one or more structural support member for providing support to the vessel. The structural support member may assist in providing structural integrity to the vessel, for example, where the vessel contains a significant volume of liquid. The support member may thus permit a lighter, more easily transportable vessel to be utilised.

Suitably, at least part of the vessel may be adapted to be constructed by a moulding process, lay up process or the like, though it will be understood that any suitable manufacturing process may be used. The vessel may be configured such that the flow path may define a stretched torus or stretched ring shape.

The shape of the vessel may be selected to assist in reducing the formation of eddies, turbulence of the like in the flow path. For example, the vessel walls may comprise smooth surfaces and/or hydrodynamically smooth wall profiles which provide low fluid resistance to the fluid travelling around the flow path.

The vessel may comprise a unitary construction. Alternatively, the vessel may comprise a plurality of modular units adapted to be coupled together to form the vessel and form the desired shape of flow path. The current forming device may comprise at least one fluid inlet.

The fluid inlet may be adapted to permit fluid to flow into the vessel. The fluid inlet may be adapted to direct pressurised fluid into the vessel. The fluid inlet may be adapted to pump aerated fluid into the vessel. It is thought that a higher oxygenation level in the fluid facilitates growth of the organism by reducing the energy required by the organism to obtain oxygen from the fluid.

Alternatively, or in addition, the system may comprise a pump unit adapted to pump fluid into the vessel via the inlet.

The fluid inlet may comprise one or more nozzle. The fluid inlet may comprise a plurality of nozzles placed at regular intervals along the inner and/or outer walls of the vessel. For example, but not exclusively, the fluid inlet may comprise two large nozzles at opposing ends of the vessel. Alternatively, or in addition, the fluid inlet may comprise a plurality of smaller nozzles placed around the periphery of the vessel.

Alternatively, or in addition, the fluid inlet may comprise one or more slot. The fluid inlet may comprise a plurality of slots placed at regular intervals along the side wall or walls of the vessel.

The fluid inlet may be directionally adjustable. For example, the angle of the or each fluid inlet is adjustable to regulate the current in the vessel

The system may further comprise a barrier member adapted to at least partially cover the inlet. The barrier member may comprise, for example, but not exclusively mesh or netting.

The vessel may further comprise an outlet.

The outlet may be adapted to drain at least some fluid from the vessel. Alternatively, or in addition, the outlet may be adapted to drain sediment or waste produced by the organism or organisms from the vessel. The outlet may comprise a shield member, for example, but not exclusively, a grate or mesh which prevents the movement of the organism therethrough. The shield member may extend across at least a portion of the base of the vessel. Thus, the shield member may comprise a raised floor or base. The raised floor may comprise a raised gauze floor to provide distance between the base and the main body of fluid within the vessel.

Suitably, the shield member may comprise one or more grate or mesh of a pore size that will prevent the organism from being drawn into the outlet and lost from the system. This may be particularly advantageous where the organism is sufficiently small in size to be drawn into the outlet. The shield member may comprise a primary and/or secondary mesh, each mesh adapted to be used with an organism of a different size or stage of maturation.

The system may further comprise a heater for heating the liquid. Furthermore, the system may be adapted to control the temperature of the liquid by selectively operating the heater. The heater may be adapted to provide a constant temperature of liquid throughout the vessel. For example, where a plurality of inlets are provided, the heater may be adapted to heat the liquid passing through each inlet to the same temperature.

Alternatively, the heater may be adapted to provide a different temperature of liquid at different areas, for example heights, in the vessel. Thus, the liquid may be heated to replicate the temperature differentiation that may occur in a natural marine environment.

The system may further comprise a lid for covering the vessel. The lid may be adapted to sealingly engage the vessel. The provision of a lid beneficially assists in preventing pollution of the liquid and/or may be used to assist in preventing spooking of the fish which may otherwise result in a flight response.

The system may further comprise one or more light source. The one or more light source may be utilised to simulate the natural environment and/or may also be used to mitigate the likelihood of spooking the organism.

The system may further comprise a filter for filtering the liquid. The system may be adapted to filter liquid from the bottom, and/or the sides and/or the top of the vessel.

Alternatively, any liquid removed from the vessel may not be filtered before being returned to the vessel. For example, the system may comprise a recirculation system that removes liquid adjacent to the inlet and then reintroduces the liquid back into the system by way of the inlet.

The system may further comprise an impact absorption member or cushioning member, for example, but not exclusively, the cushioning member may comprise foam or other suitable material adapted to absorb an impact by the organism. Alternatively, or additionally, the cushioning member may comprise netting, for example, but not exclusively, stretched netting coupled to tension springs for absorbing impacts. Fluid may be removed from the vessel at any level, including, for example, from the bottom, from the top or from any position along the side of the vessel.

According to a second aspect of the present invention, there is provided a method of housing an aquatic organism, including the steps of: providing a vessel adapted to hold a quantity of fluid therein, said vessel having at least one flow path; operating a current forming device to induce movement of fluid along said flow path; and placing an organism within the vessel wherein the organism is provided with suitable conditions to be nurtured.

The organism may comprise a species of fish and may, for example, but not exclusively, comprise larval or juvenile tuna.

At least one of the steps may be automated. The organism may be housed until it has reached a desired maturation stage and/or is of a desired size.

According to a third aspect of the present invention, there is provided an aquaculture system for use in providing an artificial aquatic environment for accommodating an organism, the system comprising: a vessel adapted to hold a quantity of fluid therein; a deflector for assisting in directing the organism away from a wall of the vessel. Another aspect of the present invention relates to the use of directional fluid flows created by one or more deflector to assist in directing an aquatic organism located within a vessel away from hitting a wall of the vessel. The directional fluid flow may be provided by one or more fluid jet. Where more than one fluid jet is provided, the fluid jets may be provided at intervals along the walls of the vessel.

The directional fluid flows may be further utilised to facilitate retention of the organism at a desired distance from the walls of the vessel. This may be achieved, for example, where at least one inlet is provided on one wall of the vessel and at least one inlet is provided on an opposing wall of the vessel.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure I is a top view of a first embodiment of a tank of^' the present invention illustrating an enlarged portion of the water flow path and fish therein;

Figure 2 is an end view of the tank of Figure 1;

Figure 3 is a side view of the tank of Figure 1; Figure 4 is a top view of a straight module of the tank of Figure 1 ;

Figure 5 is a top view of an arcuate module of the tank of Figure 1 ;

Figure 6 is a top view of a second embodiment of the tank, illustrating a nozzle system for directing the water into the tank.

Figure 7 is an end view of the tank of Figure 6. Figure 8 is a side view of the tank of Figure 6;

Figure 9 is a top view of a straight module of the tank of Figure 6;

Figure 10 is a top view of an arcuate module of the tank of Figure 6;

Figure 11 is a cross-sectional view of a third embodiment of the tank, illustrating the path of water entering the tank through a water inlet and exiting the tank through a drainage hole;

Figure 12 is a perspective view of the tank of Figure 11;

Figure 13 is a cross-sectional view of a fourth embodiment of the tank, illustrating the inflow and outflow of water;

Figure 14 is a perspective view of the tank of Figure 13; Figure 15 is an enlargement of a nozzle of Figure 14;

Figure 16 is a top view of a tank module including moulded inlets;

Figure 17 is a cross-sectional view of a fifth embodiment of the tank including inlets in the form of apertures;

Figure 18 is a side view of one of the sides of the tank of Figure 17 illustrating regularly situated apertures;

Figure 19 is a cross-sectional view of a sixth embodiment of the tank including inlets in the form of (a) multiple slots, and (b) a single slot;

Figure 20 is a side view of one of the sides of the tank of Figure 19 illustrating alternate slot arrangements (a) small number of slots, (b) large number of small slots, and (c) one single slot;

Figure 21 is a cross-sectional view of foam used as shock absorbing material on the inside of the tank;

Figure 22 is a top view of a segment of the tank illustrating placement of the foam of Figure 21 between the inlets; Figure 23 is a top view of a segment of the tank illustrating placement of the foam of Figure 21 between the nozzles;

Figure 24 is a top view of a seventh embodiment of the tank;

Figure 25 is a top view of a eighth embodiment of the tank; Figure 26 is a top view of a ninth embodiment of the tank;

Figures 27a to 27d show a tank with a series of water jets positioned at intervals along the inner and outer tank walls;

Figures 28a to 28c show a tank with a series of water jets positioned at intervals along the outer tank wall; and Figures 29a to 29d show a tank consisting of two long raceways joined at either end by half toroidal sections, with a series of water jets positioned at intervals along the toroidal sections of the tank wall.

DETAILED DESCRIPTION OF THE DRAWINGS The following detailed description of the invention refers to the accompanying drawings. Although the description includes exemplary embodiments, other embodiments are possible, and changes may be made to the embodiments described without departing from the spirit and scope of the invention. Wherever possible, the same reference numbers will be used throughout the drawings and the following description to refer to the same and like parts. Referring to the drawings for a more detailed description, an artificial environment 10 is illustrated, demonstrating by way of example one arrangement in which the principles of the present invention may be employed. The artificial environment 10, as illustrated in Figure 1, includes a vessel or tank 12 having an inner wall 14 and an outer wall 16. The walls 14 and 16 include outlets 18 adapted to direct a flow of water in the direction of arrows 20 which thereby produces a current generally defined by arrows 22. The fish 24 are able to swim against the flow of the current, as is the natural tendency of school fish, which results in adequate water flow through the gills of the fish 24. The water flow rates can be modified depending upon the development stage of the fish.

As illustrated in Figures 2 and 3 the tank 12 generally includes a base 26 and top 28 which, in combination with the walls 14 and 16, define the interior 30 of the tank 12. It is envisaged that the tank 12 will be constructed from a plurality of modules 32 and 34 as illustrated in Figures 4 and 5. Although the tank is illustrated in a modular configuration it should be appreciated the tank can be moulded as a complete unit. The tank can be made of any mouldable material and in preference, but in no way limiting, it is constructed from layered fibreglass with reinforcements to allow for structural supports. The tank has an open top 28, which may be supported by support struts (not shown) on larger versions to increase structural integrity. Furthermore, the tank 12 can include a cover (not shown) which sealably engages, the top 28. Such covers may be important to prevent pollution of the water contained within the tank in environments where there are airborne dust particles or other pollutants. Furthermore, the cover can be used to restrict the vision of the fish to prevent them being spooked.

Figures 6 to 10 illustrate an alternate configuration of the inlets 18 wherein nozzles

36 extend from the walls 14 and 16 into the interior 30 of the tank 12. In this way the angle of the nozzles 36 can be adjusted to regulate the current 22. The adjustable nozzles 36 can also be used to feed water into the tank in such a way as to create a faster moving curtain of water adjacent to the walls 14 and 16 of the tank.

This curtain of faster moving water directs fish away from the walls and toward the centre of the interior 30. The water coming into the tank can also enter at a higher oxygenation level and as a result it is expected to help the growth of the fish by reducing the energy required by the fish to obtain oxygen from the water.

Figures 11 and 12 illustrates one possible configuration wherein the inlet 18 includes a pipe 38 and moulded vent 40 which extends the height of respective walls 14 and 16. In this way water can be pumped into the interior 30 of the tank 12 in the direction of arrows 42. The water exiting the vents 40 in the direction of arrows 20 then creates the current flow 22. As further illustrated in Figure 11 the base 26 includes angled portions 44 and 46 which are inclined away from outlet 48. The outlet 48 includes an outlet pipe 50 and is configured to remove water and sedimentary waste products from the tank 12 in the direction of arrow 52.

The base includes a gauze shield 54 adapted to cover outlet 48. The gauze shield 54 is constructed from mesh of a size that will prevent the fish being inadvertently drawn into the outlet 48 and thereby lost from the system. The size of the mesh will depend on the age of the fish housed within the tank and in preference would be able to be removed for cleaning purposes. The tank may include a secondary gauze mesh layer 55 separated from the shield 54. This secondary mesh layer would be used for smaller larval stage fish.

The size of pipe 50 will depend on the total water volume of the tank 12. The pipe 50 may also include an adjustable valve (not shown) to regulate, either manually or by the way of some automated system, the water removed from the tank system. The water is then filtered by a filtration unit (not shown) before being returned to the tank via pipe 38. The system may be fully re-circulated, partially re-circulated or may be a fully flow-through system. As would be appreciated this recycling of the water has significant environmental benefits however it is not essential to the invention. The base 26 is configured to accommodate various fixtures and fittings thereby meaning that such elements as pipes and cables are safely accommodated within the tank housing and provides structural base support.

Figures 13, 14 and 15 illustrate an alternate configuration wherein the inlets 18 are in the form of adjustable nozzles 56. The adjustable nozzles 56 are attached to respective walls 14 and 16 and include a support 58 adapted to be connected to the wall, and an adjustable arm 60 pivotally attached to the support 58 by way of linkage 62.

Figures 16 to 20 illustrate various possible configurations of the inlet 18 includes apertures or slots. It should however be appreciated that the tank is not limited to any one particular configuration and that other configurations are possible and within the scope of the invention.

In one possible form of the invention the walls 14 and 16 of the tank 12 include cushioning devices 64, such as foam or netting. Figure 21 illustrates a cross-sectional view of a piece of foam 66 including air pockets 68. The foam 66 is adapted to absorb any shock of fish impacting the sides of the tank 12. The shock absorbing material can be provided in the gaps between the inlets 18 such as the moulded vents 40, as illustrated in Figure 22, and the nozzles 56, as illustrated in Figure 23. The air pockets 68 in the foam 66 can be created by large air bubbles, or by cylindrical shaped gaps that run through the foam.

It is envisaged that the foam will be attached to the walls by a non water dissolving adhesive. Furthermore, the surface of the foam in direct contact with the water contained within the interior 30 will be covered by a plastic neopolyethylene type substance or some other type of coating that is slippery or provides reduced friction when wet. This means that in the event of a fish impacting the foam the impact shock and friction are reduced.

The foam can be treated with an anti-bacterial or anti-fungal substance so that the tank environment does not become foul thereby resulting in the death or stunted growth of the fish.

It will be appreciated that the tank 12 is not restricted to an oval type configuration. Any shape that facilitates the creation of a regular flow path could be used. For instance, as illustrated in Figure 24, the tank can be circular or doughnut shaped design. Furthermore, the inlets are not restricted to a plurality of apertures or vents located regularly around the circumference of the tank. As illustrated in Figure 25 the water can be pumped into the tank by way of inlet pipes 70 at an angle to the flow path. In such a configuration a plurality of nozzles could be used to augment the action of the inlet pipes 70. Alternatively, as illustrated in Figure 26, the water can be pumped in large volumes through a gauze or mesh section 72 in the wall 16 of the tank to thereby create the current flow. In such a configuration it is envisaged that there will be an inlet conduit 74 attached to the side of the tank 12.

The tank 12 may incorporate several additional features however it should be appreciated that the invention is not limited to the use of these particular features. For example: the water entering the tank at different levels may be heated to replicate the temperature differentiations that occur in the natural marine environment; the tank can be enclosed by one or more lid; the tank can include lighting; the system filters water by taking it from the bottom, sides, or top and\or a combination thereof; water enters the tank via fixed or adjustable nozzles, slotted pipes, moulded nozzles or slots on the tank well; the tank can include foam to absorb impact from a fish hitting the walls thereby reducing the risks to the fish; the tank can have stretched netting attached to tension springs over the walls as impact protection; the tank can be round, racetrack, elliptical, or of any other configuration; the tank can be a straight length or channel with water entering from one end via a pump and exiting out the other via a drain; water may be removed at any height on the tank system, being the bottom of the tank, or the top of the tank, or any position along the side of the tank; the water removed may not necessarily be filtered before being returned to the tank, as it may be a recirculation system that pumps water out of the tank adjacent to a nozzle and then pumps the water back into the system by way of said nozzle; the water may be temperature controlled; the tank itself may be made of any material, and may or may not be segmented; the tank is made of pre-moulded segments that are cast in reinforced fibreglass; and/or the tank can have a raised gauze flooring to provide distance between the base filtration holes and the main body of water within the tank. This is particularly important when small fish are being housed within the tank as they may be sucked into the outlet.

Although the invention is primarily described in relation to the nurturing of larval or juvenile tuna, it will be appreciated that the system could be used for any aquatic fauna or flora that requires a movement of water. For instance, the apparatus could be used to house seaweed species or crustaceans such as crayfish. The tank could also be used to accommodate different life stages of any species of fish or organisms and is not limited to larval or juvenile tuna. It is envisaged that the tank is a continuous loop to allow for water recycling and continuous current flow. However the skilled addressee will appreciate that the tank does not need to be a loop and could alternatively be a straight length or channel with water entering from one end via a pump and exiting out the other via a drain. Although various means of inputting water into the tank have been described i.e. nozzles, moulded nozzles, moulded slots, water pumped into the tanks at tangent to the water flow path, the invention is not limited to these particular ways of creating a current.

The skilled addressee will now appreciate the many advantages of the present invention. The tank provides an artificial environment in which aquatic organisms such as tuna can be nurtured. The use of a single curved or partial curved flow path loop provides a simplified means of creating a constant flow of water through a tank. The configuration of the tank enables a flow path to be created which minimises the likelihood of the larval or juvenile tuna impacting the walls of the vessel thereby reducing the mortality rates caused by impact shock. This invention has been designed to create an improved tank design to allow for the raising of larger fish in an enclosed environment. Preferably, the tank system is of a modular design allowing for a range of different lengths and arcuate designs to be incorporated as required. The design is not size dependent and sections could be as wide as 5 metres or as narrow as 10 cm and there is no minimum or maximum size of the tank design, channel width or height. The construction will allow for reusable sections that, if needed, can be transported and rebuilt at any location wherever they are required.

Further advantages and improvements may very well be made to the present invention without deviating from its scope. Although the invention has been shown and described in what is conceived to be the most practical and preferred embodiment, it is recognized that departures may be made therefrom within the scope and spirit of the invention.

For example, Figures 27a to 27d, 28a to 28c and 29a to 29d show further embodiments of the present invention which relate to the provision of one more water jets placed at intervals along the walls of a tank for holding fish. The water jets are positioned at an angle to create a directional water current. The primary purpose of the water jets is to prevent fish from colliding with the tank walls by deflecting them away from the walls, or slowing them down to reduce the impact with the wall, with the water current. The water jets may also be used to encourage fish to swim at a certain distance from the walls under normal conditions, collect solid materials into one area for removal or to introduce any liquids or solids into the tank, such as feed, anaesthetic or therapeutants. The shape of the tank may be a continuous channel. In the centre of the channel the water flow can be either concurrent or counter-current to the wall flow depending on the dimensions of the tank and the flow patterns that need to be created. The number, spacing and current velocity of the water jets will be appropriate to ensure an adequate water flow is maintained along the tank walls to prevent fish from colliding with the tank walls, or at least slow them down to lessen the impact of collision. Referring in particular to Figures 27a to 27d, there is shown a tank with a series of water jets positioned at intervals along the tank walls 2, which contain the water 3. The water jets 1 are either individual water jets arranged in vertical rows (Figure 27a) or vertical strip water jets (Figure 27b). The tank walls 2 consist of a series of vertical steps and the water jets 1 are located along these steps so they are introducing water parallel to the tank walls 2.

Water is also introduced to the tank by inflow pipes 4, which create a current in the centre of the channel. The shape of the tank is either toroidal (Figure 27c) or two long raceways joined by half toroidal end sections (Figure 27d). The bottom tank wall 5 slopes towards the centre of the channel and outflow pipes 6 remove water and solid waste from the tank. In reference now to Figures 28a to 28c, there is shown a tank with a series of water jets 1 positioned at intervals along the tank wall 2, which contains the water 3. The water jets 1 are either individual water jets arranged in vertical rows (Figure 28a) or vertical strip water jets (Figure 28b). The tank wall 2 consists of a series of vertical steps and the water jets 1 are located along these steps so they are introducing water parallel to the tank wall 2. Water is also introduced to the tank by inflow pipes 4, which create a current in the centre of the channel. The shape of the tank is circular (Figure 28c). The bottom tank wall 5 slopes towards the centre of the tank and an outflow pipe 6 removes water and solid waste from the tank.

As shown in Figures 29a, there is shown a tank consisting of two long raceways joined at either end by half toroidal sections, with a series of water jets 1 positioned at intervals along the toroidal sections of the tank wall 2, which contains the water 3. The water jets 1 are either individual water jets (Figure 29b) arranged in vertical rows or vertical strip water jets (Figure 29c). Figure 29d shows a cross section of the raceway section of the tank. The toroidal sections of the tank wall 2 consists of a series of vertical steps and the water jets 1 are located along these steps so they are introducing water parallel to the tank wall 2. Water is also introduced to the tank by inflow pipes 4, which create a current in the centre of the channel. The bottom tank wall 5 slopes towards the centre of the tank and an outflow pipe 6 removes water and solid waste from the tank.

Claims

1. An aquaculture system for use in providing an artificial aquatic environment for accommodating an organism, the system comprising: a vessel adapted to hold a quantity of fluid therein, said vessel defining at least one flow path; and a current forming device adapted to induce movement of fluid along said flow path.

2. The system of claim 1, wherein the flow path is continuous.

3. The system of claim 1 or 2, wherein the flow path comprises a loop.

4. The system of any preceding claim, further comprising a deflector for assisting in directing the organism away from a wall of the vessel.

5. The system of claim 4, wherein the deflector is adapted to exert a fluid force on the organism to assist in directing the organism away from the wall of the vessel.

6. The system of claim 4 or 5, wherein the deflector comprises one or more fluid jet.

7. The system of claim 4, 5 or 6, wherein the deflector is adapted to exert a fluid force at an angle to the flow path.

8. The system of any preceding claim, wherein the organism comprises a species of fish.

9. The system of any preceding claim, wherein the organism comprises larval or juvenile fish.

10. The system of any preceding claim, wherein the organism comprises a tuna.

1 1. The system of any preceding claim, wherein the vessel comprises a base and at least one side wall which define the flow path.

12. The system of claim 11, wherein the vessel comprises more than one side wall which are substantially parallel.

13. The system of any preceding claim, wherein the vessel has a generally elliptical configuration.

14. The system of any one of claims 1 to 13, wherein the vessel has a generally circular configuration.

15. The system of any preceding claim, wherein the vessel comprises a reinforced fibreglass material.

16. The system of any preceding claim, wherein the vessel comprises one or more structural support member.

17. The system of any preceding claim, wherein at least part of the vessel is adapted to be constructed by a moulding process.

18. The system of any preceding claim, wherein the vessel is configured such that the flow path defines a stretched torus shape.

19. The system of any preceding claim, wherein the shape of the vessel is selected to assist in reducing the formation of eddies or turbulence.

20. The system of any preceding claim, wherein the vessel comprises a unitary construction.

21. The system of any one of claims 1 to 20, wherein the vessel comprises a plurality of modular units adapted to be coupled together to form the vessel and form the desired shape of flow path.

22. The system of any preceding claim, wherein the current forming device comprises at least one fluid inlet.

23. The system of claim 22, wherein the fluid inlet is adapted to permit fluid to flow into the vessel.

24. The system of claim 22 or 23, wherein the fluid inlet is adapted to direct pressurised fluid into the vessel.

25. The system of any one of claims 22 to 24, further comprising a pump unit adapted to pump fluid into the vessel via the fluid inlet.

26. The system of any one of claims 22 to 25, wherein the fluid inlet comprises one or more nozzle.

27. The system of any one of claims 22 to 26, wherein the fluid inlet comprises a plurality of nozzles.

28. The system of any one of claims 22 to 27, wherein the fluid inlet comprises one or more slot.

29. The system of any one of claims 22 to 28, wherein the fluid inlet comprises a plurality of slots.

30. The system of any one of claims 22 to 29, wherein the fluid inlet is directionally adjustable.

31. The system of claim 30, wherein the angle of the or each fluid inlet is adjustable to regulate the current in the vessel.

32. The system of any preceding claim, further comprising a barrier member adapted to at least partially cover the fluid inlet.

33. The system of claim 32, wherein the barrier member comprises mesh.

34. The system of any preceding claim, wherein the vessel comprises an outlet.

35. The system of claim 34, wherein the outlet is adapted to drain at least some fluid from the vessel.

36. The system of claim 34 or 35, wherein the outlet is adapted to drain sediment or waste produced by the organism from the vessel.

37. The system of any one of claims 34, 35 or 36, wherein the outlet comprises a shield member for preventing the movement of the organism through the outlet.

38. The system of claim 37, wherein the shield member extends across at least a portion of the base of the vessel.

39. The system of claim 37 or 38, wherein the shield member comprises a raised floor in the vessel.

40. The system of any preceding claim, further comprising a heater for heating the fluid.

41. The system of claim 40, wherein the heater is adapted to provide a constant temperature throughout the vessel.

42. The system of claim 40, wherein the heater is adapted to provide a different temperature in different areas of the vessel.

43. The system of any preceding claim, further comprising a lid for covering the vessel.

44. The system of claim 43, wherein the lid sealingly engages the vessel.

45. The system of any preceding claim, further comprising one or more light source.

46. The system of any preceding claim, further comprising a filter for filtering the fluid.

47. The system of any preceding claim, further comprising an cushioning member adapted to be coupled to the side wall inside the vessel.

48. The system of claim 47, wherein the cushioning member comprises foam.

49. The system of claim 47 or 48, wherein the cushioning member comprises netting.

50. A method of housing an aquatic organism, including the steps of: providing a vessel adapted to hold a quantity of fluid therein, said vessel having at least one flow path; operating a current forming device to induce movement of the fluid along said flow path; and placing said organism within said vessel wherein the organism is provided with suitable conditions to be nurtured.

51. The method of claim 50, wherein at least one of the steps is automated.

52. An aquaculture system for use in providing an artificial aquatic environment for accommodating an organism, the system comprising: a vessel adapted to hold a quantity of fluid therein; and a deflector for assisting in directing the organism away from a wall of the vessel.

53. The system of claim 52, wherein the deflector exerts a fluid force on the organism to assist in directing the organism away from the wall of the vessel.

54. The system of claim 52 or 53, wherein the deflector comprises a fluid jet.

55. The system of claim 52, 53 or 54, wherein the deflector exerts a fluid force at an angle to the flow path.

56. The use of directional fluid flows created by one or more deflector to assist in directing an aquatic organism located within a vessel away from a wall of the vessel.

57. The method of claim 56, wherein the directional flow is provided by one or more fluid jet.