WO2015022519A1

WO2015022519A1 - Treatment system for aquaculture

Info

Publication number: WO2015022519A1
Application number: PCT/GB2014/052463
Authority: WO
Inventors: Karl Scott
Original assignee: Marine Harvest Scotland Limited
Priority date: 2013-08-12
Filing date: 2014-08-12
Publication date: 2015-02-19
Also published as: GB201314386D0

Abstract

System, apparatus and method for treating aquaculture enclosures, wherein a constrainer (90) is adapted to isolate a volume of water containing aquaculture animals to be treated from a larger body of water, and a treatment fluid delivery device (10) is adapted for delivering a treatment agent to a volume of water containing aquaculture animals to be treated. The constrainer (90) is substantially conical or pyramidal in form, and the delivery device (10) comprising at least one hose (12), the hose (12) comprising a plurality of apertures (48, 54) along its length to allow the treatment fluid to exit therethrough.

Description

Treatment System for Aquaculture

The present invention relates to a system and component parts of the system for improving the therapeutic treatment of organisms in aquaculture, particularly, but not exclusively for the treatment of fish in fish farms. The system comprises means to isolate a volume of water in which to perform treatment, and means to deliver the treatment agent to the isolated volume of water.

Background of the Invention

The Food and Agriculture Organization of the United Nations (FAO) defines aquaculture as "the farming of aquatic organisms including fish, molluscs, crustaceans and aquatic plants". There is range of aquaculture techniques, covering a wide range of organisms, but the most common is fish farming. Fish farming involves raising fish commercially in tanks, ponds, or enclosures, usually for food. Worldwide, the most important fish species used in fish farming are, in order, carp, salmon, tilapia and catfish.

The present invention is concerned primarily with fish, and other organisms, which are farmed in enclosures or at localised sites in a large body of water, e.g. a marine environment (mariculture) or a body of fresh water, such as a lake or loch. Enclosures are required for mobile organisms such as fish, which will disburse if not contained in an enclosure, but less relevant for comparatively immobile organisms such as molluscs.

In 'cage system' fish farming (pisciculture), fish hatched and raised to a suitable size and are then placed in cages to contain and protect the fish as they grow until they are harvested. The 'cages' can take many forms, but commonly comprise a buoyant rigid structure, typically circular or polygonal, with a net hanging below to define an enclosure; such cages are also referred to as pens or net pens. Disease is a particular problem in intensive fish farming. Fish farming typically involves high population density which makes conditions favourable for pathogen transmission and multiplication. Farmed fish are often kept in concentrations not observed in the wild (e.g. 50,000 fish in a 2-acre (8, 100 m²) area). Diseases which are common in farmed salmon include:

- Ectoparasites - Sea lice, salmon fluke (Gyrodactylus salaris)

- Endoparasites - Kudoa thyrsites - Bacterial - Furunculosis (Aeromonas salmonicida)

- Amoebic - Amoebic gill disease (Neoparamoeba perurans)

- Viral - Infectious salmon anaemia virus (ISAv) Treatment of such conditions can be carried out with various therapeutic treatment agents, with have various levels of efficacy. However, it is technically challenging to treat an enclosure within a large body of water. It is desirable to minimise the amount of agent used, to minimise the effects on the surrounding ecology. However, when applied to an enclosure which is in fluid communication with the surrounding water, the agent is free to disperse away from the enclosure. To compensate for this, large quantities of agent must be used, or the organisms. Furthermore, it is impossible to know the extent to which a treatment agent has dispersed, and this results in over- or under-dosing being a problem.

Another approach is to process the organisms in a well-boat, where the organisms are pumped from the enclosure to a holding tank on the boat where treatment is administered and thereafter the fish are pumped back into the enclosure. Because the volume of the tank is known, the agent can be delivered effectively. However, well-boats are expensive and the process is extremely stressful for the organisms. One disease of particular concern at present is amoebic gill disease (AGD). This disease is primarily a disease of warm marine environments. However, it has more recently spread into colder waters of the north Atlantic, and has caused significant losses to salmon farms in Scotland and Norway. One treatment which can be effective for AGD and ectoparasites is the administration of hydrogen peroxide. Hydrogen peroxide is a useful treatment agent as it has a broad spectrum of efficacy (i.e. it can treat a large number of ectoparasites and other organisms), and it breaks down to water and oxygen, thus minimising pollution. However, treatment with hydrogen peroxide has proven highly inconsistent, and is often ineffective and at can cause unacceptable levels of mortality. The present inventors have realised that a significant problem with administration of hydrogen peroxide is that delivery of an effective but safe dose to an enclosure (e.g. a salmon pen) using conventional approaches is not practicable. Conventional approaches result in poorly distributed treatment with hotspots that can harm or kill fish. The problems observed with effective delivery of hydrogen peroxide also affect delivery of other therapeutic agents used in fish farming, such as organophosphates and acetylcholinesterase inhibitors, pyrethroids, avermectins, etc.

A conventional 'bath treatment' or 'total enclosure' system typically involves providing cylindrical or rectangular skirts or tarpaulins around an enclosure to contain the volume of water to which the treatment agent is applied. This is typically labour-intensive and it is difficult to deploy known tarpaulin systems. Prevention of reinfection is a challenge since, using existing technologies, it is practically impossible to treat an entire pen in a short time period. Since the volume of water is very imprecise using known tarpaulin systems, the required concentration of treatment agent is not guaranteed. Crowding of fish to reduce the volume of drug required can also stress the fish. Recent use of well-boats containing of active agents has reduced both the concentration and environmental concerns, although transferring fish to the well boat and back to the cage is stressful. As touched on above, the use of a well boat is expensive and there are relatively few well boats in operation. The difficulties with existing enclosure systems results in failed treatments, unacceptably high mortality rates and repeat treatments are often required.

There is a need for improved treatment techniques for administering treatment agents for treating AGD and other diseases in aquaculture.

Statements of the Invention

According to the present invention, there is provided a treatment system for treating an aquaculture enclosure, the system comprising

a constrainer formed from flexible sheet material, the constrainer having a generally conical or pyramidal form, the constrainer being adapted to surround a enclosure containing organisms to be treated, and

a treatment fluid delivery device comprising at least one hose, the hose comprising a plurality of apertures along its length to allow the treatment fluid to exit therethrough.

Suitably the system also comprises a pump apparatus adapted to pump a treatment fluid into the delivery device.

Constrainer

The term 'conical' in the present context includes circular cones and elliptical cones. The term is not restricted to perfect geometrical examples of cones, but includes minor variations therefrom, e.g. where the sides are not completely straight or the base is not perfectly circular or elliptical. The term 'generally conical' in intended to reflect this.

Likewise, the term 'pyramid' is intended to cover a pyramid a polyhedral base and sides leading to an apex. The base can be a regular polygon or an irregular polygon. The term covers variations from perfect pyramids, e.g. where the sides of the base or the sides of the pyramid are curved to some extent.

Frustums (i.e. frustoconical and frustopyramidal shapes are also included, provided that they are not truncated such that the perpendicular height is reduced by 1/3 compared with the corresponding intact cone. Preferably any frustum is only truncated slightly (e.g. by less than 10%) compared with the corresponding non-truncated form.

Typically the base of the cone or pyramid substantially corresponds to the shape of the enclosure about which the constrainer is to be deployed; such enclosures are typically round or polygonal.

The shape of the constrainer is, of course, defined in terms of its shape when in use, i.e. fully opened up. Because the constrainer is flexible, it can of course be collapsed, bundled or folded into other shapes. What matters is, of course, the shape of the constrainer in use, i.e. when deployed as part of a treatment system.

The constrainer is suitably a tarpaulin. Tarpaulin is a generic term applied to large sheets of water-resistant or waterproof materials. This is the term used in the art to refer to sheets used to enclose a treatment volume for administering a therapeutic agent to fish cages.

For the present invention it is typically preferred that the sheet material from which the constrainer is formed is substantially waterproof. It is not necessary that the constrainer is completely waterproof, but it is certainly possible that it can be. It is necessary that the constrainer is able to isolate a volume of water from the surrounding water, and thus provide a substantially isolated volume in which a treatment agent can be administered. Complete isolation is not typically required and the fact that a small volume of water can pass across the constrainer is not generally problematic, but generally it should be minimised as far as practicable. The volumes constrained by the constrainer in the case of typical pens used in salmon farming can be from 500 to about 36,000 cubic meters and therefore the fact that a few tens or even hundreds of litres can pass across the constrainer during the course of a treatment makes very little difference to the overall volume; what matters is that the bulk of the water is constrained for the duration of the treatment.

Suitable materials for the tarpaulin include polypropylene, canvas, vinyl, nylon, etc. The tarpaulin can comprise a plurality of different materials, e.g. as a laminate. One suitable sheet material is nylon fabric, e.g. from 300 g/m² to 500 g/m².

The constrainer can comprise a plurality of panels which are joined together. Preferably the tarpaulin with comprise reinforcing strips, e.g. webbing. These reinforcing straps can be arranged to align with the main forces applied to the constrainer during installation and/or removal, or when deployed in situ. For example, webbing can be aligned with lifting/haul points. Suitably there is a substantially continuous stretch of webbing around the perimeter of the constrainer, e.g. formed of 75 mm webbing.

Suitably lengths of webbing run from the lifting/haul points on the perimeter of the constrainer to the apex, e.g. formed of 100 mm webbing.

In a particularly preferred embodiment the constrainer is formed from a plurality of triangular panels joined to form a pyramid, each triangular panel defining one face of the pyramid. The triangles panels are preferably isosceles triangles. For example, the constrainer can be formed from a plurality of identical isosceles triangular panels, the triangles being arranged to meet at theirs points, thereby defining the apex of the pyramid, with the base of the triangles defining the perimeter of the constrainer. Each triangular panel triangle is joined to its neighbour along its sides. In such an embodiment reinforcing straps can be provided running along the joins between the panels. In an alternative embodiment the constrainer can be conical. Such a conical constrainer can be made from panels having an appropriate shape (e.g. roughly triangular, but having curved sides), or it can be formed from a single sheet.

A significant advantage of the present invention is that it allows for a well-defined and predictable volume to be isolated. Prior art tarpaulin systems do not allow this to be achieved. In the prior art the strategy has been to minimise the volume isolated by the tarpaulin, and therefore the tarpaulins used have generally matched the shape of the pen, i.e. being cylindrical or rectangular. However tarpaulins having such shapes are greatly affected by forces imparted by movement of water, such as currents or tidal flows, and by wind. As a result, the shape, and therefore the volume, isolated by the tarpaulin in practice does not match that which was intended. This means that the volume for treatment is not well characterised, and the treatment becomes prone to error. The end result of this is that treatment programs in prior art systems are largely guesswork regarding dosage rates, and are prone to overdosing.

In contrast, where a substantially conical or pyramidal constrainer is used, it is possible to consistently isolate a well-defined volume. One reason for this is that, with a conical or pyramidal constrainer, a weight can be suspended from the apex of the pyramid or cone. This has the effect of pulling the constrainer into the intended shape. Another reason is that the conical or pyramidal shape is not as prone to deformation as a rectangular or cylindrical shape when hydrodynamic forces are applied to it. Whilst the conical or pyramidal shape can, of course, still be distorted by hydrodynamic forced to some extent, it will tend to return to the correct shape under the action of the attached weight.

Accordingly, in a preferred embodiment the constrainer is adapted to facilitate weighting of the apex in use. For example, the constrainer can comprise attachment means for attachment of a weight to the apex thereof. The present invention also provides a constrainer with a weight associated with the apex. The weight can be attached below the apex, e.g. hanging therefrom, or it can be provided inside the constrainer, in which case it can simply lie at the bottom of the cone or pyramid. Preferably the constrainer is provided with a plurality of primary attachment points along its perimeter, i.e. the geometrical base of the cone or pyramid. Suitably these attachment points (lifting/haul points) are located at joints between adjacent panels, and preferably these attachment points are connected to reinforcement straps, e.g. webbing straps (e.g. 100 mm) as mentioned earlier. Such reinforcement straps can run from the perimeter substantially to the apex of the constrainer. Such attachment points provide suitable locations for attaching connectors to assist with deployment or retrieval of the constrainer, and/or for connecting the constrainer to the superstructure of the enclosure, which is typically a floating wharf around the perimeter of the enclosure. The attachment points can suitably comprise eyes, hooks, karabiners or the like (stainless steel rings, e.g. 75mm ID ring formed of 20mm diameter steel, are a preferred type of fixing at the lifting/haul points). Additional secondary attachment points can be provided at intermediate points between the primary attachment points. These are typically used in the installation process to manually tie the secondary attachment points to the perimeter to the pen. They are not typically subject to such high forces as the main attachment points, which are typically winched into place, and thus thinner webbing can be used to provide reinforcement (e.g. 50 mm wedding and 50 mm by 10 mm rings).

Suitably the reinforcing straps mentioned above continue below the apex to form a plurality of loops. These loops provide a suitable attachment point for hauling the apex of the constrainer, e.g. during installation and retrieval, and for affixing a weight. Suitably a sling is fastened running through said loops. Optionally the reinforcement strap are continuous in that they pass from a first point the perimeter to the apex, and then loop back up the perimeter, e.g. to a second point diametrically opposite the first point. Parts of the constrainer can be colour coded to assist in installation. For example, the attachment points can be colour coded to help identify which attachment points should be attached to specific anchors on the pen superstructure or used during the

deployment/retrieval process. This is particularly useful because the constrainer has a large area and it can be difficult to identify the specific parts of the constrainer when it is bundled or folded up for storage or transportation. The colour coding can suitably be adapted correspond with colour coding provided on the enclosure or on the deployment apparatus such as winches and the like. Colour coding can conveniently be achieved by using webbing of different colours and/or providing coloured fabric at various attachment points. For example, the primary attachment points which are winched by a first boat during the deployment process can be labelled with a first colour and those winched by a second boat can be labelled with a second colour.

In one embodiment of the invention the constrainer is provided with a system to allow for the volume of the constrainer to be modified. For example, this can conveniently be achieved through the provision of a system to pull the conical or pyramidal constrainer tight to form a secondary apex at a shallower level than the primary ('true') apex of the constrainer. This will result in a constrainer with the same diameter at the perimeter, but a shallower depth and less steeply sloped sides. This can be achieved, for example, by providing a draw-cord running around the circumference of the constrainer at an intermediate position between the apex and the perimeter, for example at a location approximately one third of the total depth of the constrainer from the 'true' or 'primary' apex. The draw-cord can suitably run through a number of runners (e.g. eyelets) on the outer or inner surface of the constrainer. Preferably the draw-cord does not require any holes through the constrainer, which would allow water to pass through them. When the draw-cord is pulled tight, the constrainer is pulled tight and a secondary apex is formed. The constrainer can suitably be provided with a pump to fill the constrainer with water. This can be useful in certain circumstances to top up the water within the constrainer. Suitably the pump comprises and air lift pump. Suitably the air lift pump comprises a riser tube having an inlet and an outlet, the outlet discharging into the constrained volume, and a source of air (e.g. compressed air) for introduction into the riser tube to reduce the density of water within the riser tube. Suitably the outlet of the riser tube is at or near the apex of the constrainer. A suitable compressor can be provided on the pen or a vessel used for the installation process.

It will be apparent to the skilled person that the volume of a cone or pyramid can be calculated by the general formula 1/3 x base area x perpendicular height. For a cone this equated to 1/3τττ²Ιι, where r is the radius of the circle and h is the perpendicular height (i.e. the perpendicular distance from the base to the apex. Using these formulas it is easy for the person skilled in the art to determine the volume of water constrained by the constrainer, and calculi appropriate dosage of a therapeutic agent.

For example, a typical round salmon pen has either a 100m or 120m circumference. For a constrainer having a total depth at its apex of 10 meters, that gives a volume of 2926 m³ for a constrainer for a100m pen and 4081 m³ for a constrainer for a 120m pen. Table 1 provides more details of various pen sizes and constrainer measurements.

Table 1

Pen size Tarp Circumference Tarp Apex Depth Tarp Volume

126 12 4897

120

126 10 4081

126 8 3265

104 12 3511

100 104 10 2926

104 8 2341

25x25 12 2304

24 (square) 25x25 10 1920

25x25 8 1536 In one embodiment of the invention the constrainer is provided with buoyant means at least a portion of the perimeter. Suitably the buoyant means comprises at least one inflatable body. For example, the buoyant means can comprise one or more inflatable bags which are adapted to be selectably inflatable, e.g. using a supply of compressed air. Such buoyant means can be useful in installing the constrainer as they can be used to aid raising of the constrainer into position. The ability to inflate and deflate the buoyant means as required is extremely useful as the inflatable body can be inflated once the constrainer has been pulled into position under the pen, and deflated when removal is required. It is preferred that the buoyant means is provided around less than the entire perimeter of the constrainer; in other words at least a portion of the perimeter is not inflatable. For example, and arc of between 120 and 240 degrees of the perimeter can suitably be provided with buoyant means which allows this part of the perimeter to be floated into position. This is desirable as inflatable means is only provided in regions where it is required. At least part of the perimeter is typically fixed to the pen very early in the process of installation, and thus there is no need to use buoyancy to assist in raising it into position and omitting it from this part can actually simplify construction and deployment. The buoyant means can be continuous or discontinuous around the perimeter of the constrainer. Treatment Agent Delivery Device

The delivery device preferably consists of at least one lateral hose adapted to extend across the surface of the volume of water to which a treatment agent is to be delivered, and at least one branch hose connected to said lateral hose adapted to extend downwards into the volume of water to be treated.

More preferably the delivery device comprises a plurality of lateral hoses adapted to extend across the surface of the volume of water, with each lateral hose comprising at least one branch hose.

Preferably the at least one lateral hose, and any branch hoses present, are substantially sealed at their ends, e.g. by a cap, or flow through the ends is significantly restricted compared to flow through the main length of the hoses. This means that the fluid within the hoses is forced to exit the delivery device via the plurality of apertures provided on the hoses. If the ends of the hose were open, then the fluid would easily flow out of the hose through the ends, and only a small proportion of the fluid would exit via the apertures. By using substantially sealed ends, pressure within the delivery device can be increased and substantially all of the fluid can be forced to exit via the apertures. Of course, the ends of the hoses can provided with one or more apertures, provided that these are of sufficiently small cross-sectional area to allow correct delivery of the treatment fluid. Preferably at least one lateral hose is adapted to be buoyant during use such that it floats at the surface of the volume of water to be treated. More preferably all lateral hoses are adapted to be buoyant. Buoyancy can be achieved by providing floats at various points along the length of the lateral hoses, or substantially continuously along the length of the hose. Alternatively, the hose can be formed from an inherently buoyant material.

Preferably any branch hoses are adapted to be negatively buoyant so that they sink into the volume of water to be treated. More preferably all branch hoses present are adapted to be negatively buoyant. Negative buoyancy can be achieved by providing a weight on the branch hose, e.g. at the end of the branch hose. In some cases the branch hoses may be inherently negatively buoyant when in use, in which case weights are not required.

The overall intention of the delivery agent is to provide well-distributed delivery of the treatment agent to the volume of water to be treated. This is achieved by providing a plurality of delivery points via the apertures in the delivery device. Furthermore, the distributed delivery of the treatment agent is facilitated by having a plurality of hoses which reach into the volume to be treated and thus reduce the amount of diffusion required to dose the entire volume. The principle can perhaps be summarised as delivering a large number of localised doses dispersed throughout the volume to be treated. Clearly there are a number of possible arrangements of lateral and branch hoses which can used to achieve the desired result of dispersed delivery of the treatment fluid. Several possible exemplary configurations will be described below, but other arrangements are of course possible. In a first embodiment, which is particularly well-suited for treating a circular pen, the delivery device comprises:

a feed conduit adapted to connected to a source for supplying the treatment fluid under pressure;

a splitter (e.g. a manifold) to split the fluid flow from the feed conduit into a plurality of lateral hoses adapted to be deployed in parallel across the surface of the treatment volume; each lateral hose being provided with a plurality of branch hoses adapted to extend downwards into the treatment volume when the device is deployed.

In a geometrical sense the lateral hoses can be considered to be arranged as generally parallel chords in respect of the circular pen. Preferably the lateral hoses are adapted to be approximately equally spaced across from each other across the surface of the pen.

For example, one can consider a system involving 3 substantially rectilinear lateral hoses, one central lateral hose running across the diameter of the pen, and two side lateral hoses others lying in parallel on either side, each being halfway between diameter and the edge of the pen. Other arrangements of hoses can, of course be envisaged, e.g. 4, 5, 6 or more lateral hoses.

Additionally, the one or more lateral hoses could be curvilinear. For example, the lateral hose could define one or more circles, ovals, curves or the like. In one example one can envisage a plurality of generally circular lateral hoses of varying diameters, arranged in a generally concentric manner. Branch hoses could be provided descending from the lateral hoses. The number and length of the branch hoses is adapted depending on the shape of the volume to be treated. The general idea being that the branch hoses will descend into the treatment volume until they reach, or nearly reach, the bottom of the treatment volume. For a conical or pyramidal volume the branch hoses which branch nearer the middle of the lateral hoses will be longer than those which branch towards the ends of the lateral hoses, i.e. those descending in the middle of the pen will be longer than those towards the edges of the pen.

In the case of 3 lateral hoses, as mentioned above, the central lateral hose can have, say, 5 branch hoses, evenly spaced along its length, the middle branch hose being the longest, the two on either side of that being shorter, and the two beyond those being yet shorter still. The two side lateral hoses can comprise, say, 5 branch hoses, with a similar pattern in the length of the branch hoses. However, the length of the branch hoses extending from the side lateral hoses is less than those of the central lateral hoses, reflecting the fact that the side lateral hoses lie above a shallower part of the treatment volume.

It should be noted that the diameter of the hoses can be varied within the delivery device. For example, hoses which have to carry a large volume can have a given diameter and those which have to carry a smaller volume can have a smaller diameter. Thus 'arterial' hoses which require a large capacity, such as the feed hose and portions of a hose near to the treatment source, might have one diameter, and branch hoses such, especially near the ends of the branch hoses might have a second, smaller diameter reflecting the lower capacity they need to carry the required amount of treatment agent.

The apertures can optionally comprise nozzles to modify the flow of fluid therethrough, e.g. to restrict flow or to modify the flow to form a spray or the like. Preferably the delivery device comprises one or more collars which are provided with apertures through which the treatment fluid flows.

The collars suitably comprise a cylindrical body, the wall of which comprises one or more apertures. The apertures suitably pass radially through the wall of the collar. For example, a collar can comprise one, two three or more radial apertures circumferentially spaced around the collar.

It is preferred that the apertures are configured such that, in use, they direct the flow of treatment fluid into the volume of water to be treated. That is to say, that it is preferably avoided that the apertures are positioned such that treatment fluid is directed into the air above the volume of water to be treated. It will be appreciated that there will be less resistance to expelling a treatment fluid into a gaseous medium (i.e. air) than into a liquid environment (i.e. water), and this would mean that flow through the apertures could be unbalanced if one or more apertures exited into the air above the water to be treated. The desired configuration can be achieved by ensuring that all apertures are positioned such that they exit below the water surface when the device is deployed. If the entire hose is submerged then the direction in which the apertures exit will typically not be an issue.

Suitably the collars house nozzles which define the apertures through which the treatment fluid flows. For example a collar can comprise an aperture into which a nozzle is mounted to define the flow aperture through which the treatment fluid flows.

Preferably the apertures comprise removable nozzles. For example, the nozzles can be removably mounted in in apertures provided in collars. For example, the nozzles can comprise an annular member having an external and an inner diameter, the external diameter corresponding to the size of the aperture in a collar, and the inner diameter defining the cross-sectional area of the flow-path through the nozzle. In one embodiment the nozzles are mounted in a bore through the wall of a collar. Suitably the bore comprises a screw thread which corresponds to a thread provided on the outside of a cylindrical nozzle; the nozzle can thus be screwed into the bore. To facilitate this the nozzle can be provided with a drive means, e.g. a hexagonal recess to receive a suitably sized Allen key. Alternatively the bore can have a shoulder against which the nozzle abuts, and a retainer fitted into the bore to retain the nozzle in place, e.g. with the nozzle sandwiched between the shoulder and the retainer. The retainer can screw into a thread provided in the bore. Other arrangements are perfectly possible, e.g. the nozzle could be an interference fit with the aperture in the collar.

Preferably the delivery device comprises a plurality of apertures, some of which have different flow rates from others. For example, the device can comprise a first set of nozzles which define an aperture having a first cross-sectional area, and a second set of nozzles which define an aperture having a second cross-sectional area. It will be appreciated that flow through a particular aperture is governed primarily by the cross-sectional area of the nozzle, more specifically the cross-sectional are at the narrowest point of the nozzle.

Accordingly, by specifying the cross-sectional area of the aperture at a given location on the delivery device, the flow through that specific aperture can be controlled. In the context of the apertures, the term 'size', or related terms, will be used for brevity to refer to the cross- sectional area of the aperture.

The inventors have used apertures from 7 to 13mm for the various volumes which have been dosed. A typical delivery device for a 100 pen has apertures of 8, 10mm and 12mm. For larger pens the number of hoses, doser units and/ or the aperture size can be increased.

The provision of varying aperture sizes in the delivery device has a number of benefits, including:

- Pressure drop along the length of the hoses of the delivery device can be compensated for. More specifically, at increasing distances from the pressure source along the hoses of the delivery device, where pressure drop will have occurred, larger apertures can be used to ensure balanced delivery of the treatment fluid along the length of the various hoses.

- Delivery rate of the treatment fluid through the aperture can be tailored to the volume of liquid which the aperture is intended to dose. For example, where an aperture is intended to dose a large target volume a comparatively large aperture can be used, but where the aperture is intended to dose a smaller volume a smaller aperture can be used. For example, apertures located in use adjacent to the constrainer may dose a lower volume than an aperture located in a 'free' volume of liquid towards the centre of the constrained volume. Where the apertures are adapted to be adjustable then this provides additional advantages. For example, the overall delivery rate of the delivery device can be modified without the need to adjust pumping rate or pressure. Where a lower delivery rate is required, the aperture sizes throughout the delivery device can be reduced. Where a higher delivery rate is required, the size of the apertures can be increased. A lower delivery rate might be required for treatment fluids where lower dosage levels are required or where there is an increased need to allow for diffusion of the treatment fluid, e.g. to avoid 'hot-spots' developing due to rapid delivery and accumulation of the treatment agent.

It would be a matter of routine for the skilled person to determine suitable aperture sizes at various positions of the device to provide a suitable balanced delivery for the delivery fluid of interest.

The objective is typically to balance delivery of the relevant treatment agent and diluent (i.e. typically water) and the delivery device. The apertures used typically allow the dosing unit to be used at full capacity (i.e. water flow) and the amount of peroxide or other treatment agent being added. As a rule of thumb if the user calculates the cross-sectional area of a delivery device main hose (e.g. the thickest point on the lateral hoses) and calculates the total aperture surface area served by that hose to be slightly lower than this, e.g. between 2/3 and equal to this figure, then a suitable balance is typically achieved. Typically the apertures should be sized so that the pressure in the system is maintained at a relatively high level, as it improves mixing when the liquid leaves the aperture under pressure.

In a preferred embodiment the delivery device comprises a plurality of sections of hose joined by coupling members, the coupling members being adapted to allow flow between the sections of hose.

The couplers can be adapted to join two or more hoses together. For example, the couplers can be linear, i.e. to join two hoses together in a straight line, or they may be a T-piece, i.e. to join three hoses together in a T arrangement. Other forms of couplers such as elbows, crosses and the like could of course be used. An advantage of the use of a plurality of sections of hose joined by couplers is that it allows a modular construction of the device. Thus a delivery device can be readily constructed to fit any volume or shape by adding or removing sections. Another advantage is that is allows damaged sections to be conveniently removed and replaced.

Suitably the linear couplers can comprise apertures for delivery of the treatment fluid. For example, the couplers can comprise the collar as discussed above. Other couplers could of course also be provided with apertures. An exemplary linear coupler comprises a generally cylindrical body, the body having an annular shoulder projecting outward from the body approximately at its middle. The annular shoulder has a larger external diameter than to portions to either side of it. The cylindrical portions either side of the annular shoulder define interface portions adapted to slide into the end of the hose sections, i.e. their external diameter is substantially the same as the internal diameter of the hose, perhaps slightly smaller, or perhaps larger if the hose is stretchable. The interface portions can optionally be tapered such that the hose tightens upon the interface portion as it is slid onto the interface portion.

Suitably the hose is fixed to the coupler by a suitable fixing means. The fixing means can be an adhesive or a mechanical retainer. For example, an adjustable collar or a crimp can be provided to compress the hose onto the coupler. It is preferred that the fixing means does not create any snagging points on the dosing device. Crimps used on hydraulic hoses are an ideal type of fixing means as they allow for a strong attachment and provide a smooth exterior surface which avoids snag points. For example, jubilee clips are typically

undesirable as they provide sharp edges and projections which mean that the delivery device will be likely to snag, and therefor damage, nets, the constrainer and other components of a pen/cage during deployment and retrieval.

It is a preferred feature of the present invention that it is free from potential snag points.

In a preferred embodiment the delivery device comprises a collapsible hose, e.g. hose made of a fabric that, in the absence of a positive internal pressure, will collapse to some extent. Suitable hoses are well known in the art. The advantage of using such a hose is that is permits easy storage, e.g. by coiling the hoses of the delivery device around a drum or the like.

Other Components of the Treatment System The system may further comprise a pumping system to pump the treatment fluid into the delivery device. Suitably the pumping system is as described in co-pending application GB In a further aspect the present invention provides a constrainer formed from flexible sheet material, and having a generally conical or pyramidal form, the constrainer being adapted to enclose an aquaculture enclosure containing organisms to be treated.

Various preferred embodiments and features of the constrainer are discussed above.

Such a constrainer has significant advantages when used in various other circumstances, e.g. without the fluid delivery device. For example, it can be used in any situation where there is a requirement to constrain volume of water around an aquaculture enclosure, e.g. during treatment or research.

In a further aspect the present invention provides a treatment fluid delivery device comprising at least one hose, the hose comprising a plurality of apertures along its length to allow the treatment fluid to exit therethrough. Various preferred embodiments and features of the fluid delivery device are discussed above.

Such a fluid delivery device has significant advantages when used in various other circumstances, e.g. without the constrainer of the present invention. For example, it can be used in any situation where there is a requirement to deliver a treatment agent in a well- distributed manner to a volume of liquid to be treated. For example, it might be used to treat a pond or pool.

In another aspect the present invention provides a method of preparing an aquaculture enclosure situated in a body of water to facilitate administration of a treatment agent, the method comprising:

- providing a constrainer formed from flexible sheet material, and having a generally

conical or pyramidal form, the constrainer being adapted to enclose an enclosure containing organisms to be treated;

- enclosing said enclosure with the constrainer and thereby isolate the constrained volume of water from the larger body of water in which the enclosure is situated; - providing a treatment fluid delivery device comprising at least one hose, the hose comprising a plurality of apertures along its length to allow the treatment fluid to exit therethrough; and

- deploying the treatment agent delivery device into the constrained volume of water.

The method may suitably comprise weighting the constrainer to promote adoption of the intended conformation. For example, a weight can be hung from the apex of the cone or pyramid. Suitably the method further comprises delivering the treatment agent to the constrained volume of water.

Suitably the treatment agent is hydrogen peroxide. Preferably the hydrogen peroxide has been diluted from a concentrated form to a diluted form prior to passage from the delivery device to the volume of water to be treated. For example, hydrogen peroxide at, say, 50 % v/v in water can be diluted to 25 % v/v in water, or lower, e.g. from 1 % to 15 % v/v in water.

The treatment agent can, however, be any treatment agent suitable for use in aquaculture. Such treatment agents include, for example:

- Organophosphates,

- Acetylcholinesterase inhibitors,

- Pyrethroids, and

- Avermectins Pre-dilution of any treatment agent is desirably in the present invention. Typically treatment agents are provided in pure or concentrated solutions or in solid forms to minimise transport cost. However, administration of a concentrated treatment agent increases the risk of creating hot-spots, which result in localised over-dosing. This can be harmful or even fatal to the organisms being treated. By pre-diluting the treatment agent, e.g. with water, to form a pre-diluted treatment fluid then the risk of hotspots can be reduced or avoided entirely. Additionally, by delivering a large volume of a diluted treatment fluid, rather than a small volume of a concentrated treatment fluid, it is possible to deliver higher volumes at comparatively high flow rates; this results in turbulence at the point of delivery which results in improved diffusion of the treatment agent within the volume to be treated. The treatment delivery rates obviously vary depending on the constrained volume, biomass to be treated, water temperature etc. Various examples of treatment volumes and other parameters are shown in Fig 16; in this case the target peroxide concentration was 1600 ppm and delivery strategies for three pens (100 and 120 m circumference circular pens and a 24x24 square pen). Fig 17 shows various volumes (in litres) of 50% by volume H₂0₂ required to treat various pens sizes for various constrainer apex depths to a desired H₂0₂ concentration; this H₂0₂ is preferably delivered along with a diluent, e.g. seawater, to reduce the concentration and thereby reduce the risk of harming fish in the pens. The method may further comprise oxygenating the volume of water to be treated. This can be achieved by providing a source of oxygen via the delivery device. For example a flow of oxygen gas can be introduced into the delivery device, or oxygen can be dissolved in the treatment fluid. According to a further aspect of the present invention, there is provided a method of isolating an aquaculture enclosure from the body of water in which it is situated, the method comprising:

conical or pyramidal form, the constrainer being adapted to enclose an enclosure containing organisms to be treated; and

- enclosing said aquaculture enclosure with the constrainer and thereby isolate the

constrained volume of water from the larger body of water in which the enclosure is situated. Preferably the method comprises installing the constrainer against a tidal flow (any other appropriate bulk flow of water, e.g. a current) in order to ensure substantially complete filling of the constrainer with water.

Preferably the method comprises providing a weight on the apex of the constrainer.

Preferably the method comprises providing one or more weights on the perimeter of the constrainer to ensure that the perimeter of the constrainer sinks into the body of water and thereby allow water to enter the constrainer. Preferably the method also comprises the step of retrieving the constrainer. Preferably retrieval comprises hauling on the apex of the constrainer to cause the constrainer to empty as it is hauled. According to a further aspect of the present invention, there is provided a method of treating a volume of water with a treatment fluid, the method comprising:

- providing a treatment fluid delivery device comprising at least one hose, the hose

comprising a plurality of apertures along its length to allow the treatment fluid to exit therethrough;

- deploying the treatment agent delivery device into the volume of water; and

- delivering the treatment fluid to the volume of water. Specific Description of the Invention

Embodiments of the present invention will now be disclosed, by way of non-restrictive example only, with reference to the accompanying drawings, in which:

- Fig 1 shows lateral and branch hoses of a treatment fluid delivery device according to the present invention;

- Fig 2 shows a plan view of the arrangement of the lateral hoses of the device of Fig 1 when in use in a circular pen;

- Fig 3 shows part of a branch of the delivery device in which two sections of hose are joined by a coupler which is provided with an aperture;

- Fig 4 shows a T-piece coupler joining 3 section of hose at the junction of a lateral hose and a branch hose, and a float to provide positive buoyancy to the lateral hose;

- Fig 5 shows a coupler in which a removable nozzle is inserted;

- Figs 6a and 6b show the end of a lateral hose, with a removable end cap removed or in place - the rope attached to the end cap aids in deployment of the delivery device; - Fig 7 shows an end cap of a branch hose, and comprises an aperture;

- Fig 8 shows a cross-section of a coupler;

- Fig 9 shows a cross-section of a leg portion of a T-piece coupler;

- Fig 10 shows a cross-section of cross piece (horizontal portion) of a T-piece coupler;

- Fig 11 shows a cross-section of an end piece for a branch hose (down-leg);

- Fig 12 shows a cross-section of an end piece/removal cap for a lateral branch hose;

- Fig 13 shows a schematic of a constrainer of the present invention from the side;

- Fig 14 shows a bottom view of the constrainer; and

- Fig 15 shows colour coded attachment points at the perimeter of the constrainer and webbing re-enforcement strips. - Fig 16 shows exemplary H₂0₂ delivery protocols for 3 different constrained volumes. Target peroxide concentration was 1600 ppm and the three pens are 100 and 120 m circumference circular pens and a 24x24 square pen.

- Fig 17 shows various volumes (in litres) of 50% by volume H₂0₂ required to treat various pens sizes for various constrainer apex depths to a desired H₂0₂

concentration.

- Fig 18 shows the distribution of various aperture sizes on the central portion of the delivery device of Fig 1 The present invention relates to improving methods for treatment of aquaculture enclosures. Of particular interest are fish pens/cages located in oceans or lochs/lakes or the like.

However, the invention has utility in treating any type of aquaculture enclosure in which organisms are held in enclosures which sit in a larger body of water. The problems associated with known systems for constraining and isolating a volume of water for treatment include:

- Unpredictable volumes of water constrained.

- Difficult to deploy / retrieve known tarpaulins.

- Duration of time to take in deploying and retrieving the tarpaulin is excessive.

- Negative effects on fish health and therefore reduced treatment success rates.

- Unable to treat large number of units per day.

- Excessive time taken to complete one site (importance in reducing infestation pressure from untreated pens).

- High service costs and down-time due to failures.

- Tarpaulins expensive to produce.

- Not easy to disinfect tarpaulin (between sites/locations)

- Poor mixing and 'hot' and 'cold' spots due to shape and more importantly unpredictable volumes.

- Bulky designs had to be made from lighter materials to make handling easier but this made them more prone to failure.

- More equipment and personnel required.

- Not user or fish friendly.

The problems associated with known dosing systems include:

- Unpredictable distribution / poor mixing of products within the volume to be treated

- Lack of capacity for high volumes of water and product - Hot and cold spots within the treatment volume

- Poor results/efficacy, failed treatments which require a follow up treatment

- Treatment doses increased to make up for the inferior distribution. Higher costs and more risk of overdosing.

- Increased use of product.

- Builds resistance to products.

- Higher risk of mortality.

- Lack of focus on the importance of the setup from personnel. Standardized design allows SOP to be drawn up and followed.

- Systems are not snag free, which carries a risk of damage to nets.

- Difficult to deploy and retrieve.

The present invention provides improved an improved delivery device and an improved constrainer. The delivery device and constrainer are adapted to work together to allow efficient and effective treatment of aquaculture enclosures. Each of the delivery device and the constrainer can, however, be used independently of each other. For example, the delivery device can be used to deliver a treatment fluid to any volume of water to be treated, e.g. a tank. The constrainer can be used to constrain a volume of water for treatment with a device other than the delivery device of the present invention.

Referring to Fig 1 , key components of a treatment fluid delivery device 10 are shown in. The components are shown in a vertical orientation for convenience, with the lateral hoses sunning vertically, and the branch hoses running horizontally on the page. In use, the lateral hoses run across the top of the water, with the branches descending downwards.

The key components of the delivery system 10 include a central portion 12 and two side potions 14a, 14b. Each portion comprises a lateral hose and five branch hoses 22,24,26. The lateral and branch hoses comprise a plurality of hose sections 16, which are joined to each other via couplers, in the form of straight couplers 18 and T-piece couplers 20. The couplers are provided with apertures through which the treatment fluid can exit the delivery device 10. Floats 30 are provided on the lateral hoses so that they are buoyant and thus remain at the surface of the volume of water to be treated. The end of the lateral hoses are provided with end caps 32, which comprise apertures for delivering the treatment fluid.

Likewise, the end of the branch hoses are provided with end caps 34, which comprise apertures for delivering the treatment fluid. As can be seen from Fig 2, in use the central portion of the delivery device 10 extends across the diameter of a circular enclosure 30. The side portions 14a and 14b extend across parallel chords, approximately halfway between the diameter and the distal edge of the enclosure. It will be apparent to the skilled person that many other arrangements of the delivery device are possible. For example, there could be more or fewer lateral hoses, or the lateral hoses could be curved or the like.

The branch hoses descend from the lateral hoses, essentially vertically, into the volume to be treated. As can be seen from Fig 1 , the length of the branch hoses varies along the length of the lateral hoses. The length of the branch hoses is adapted to complement the shape of the isolated volume of water defined by the constrainer, which will be described below. It is of course possible that the delivery device can be used without a constrainer, and in that case the branch hoses can be adapted to any suitable length, e.g. to match the shape of an enclosure.

Not shown in the figures are feed lines which extend from a pumping apparatus to the lateral hoses. These feed conduct the treatment fluid from the pumping apparatus to the lateral hoses. Fig 3 shows a coupler 40 of the present invention coupling two sections of hose 42,44 together. As can be seen, the hose is flexible and, in the absence of positive pressure within the lumen of the hose, collapses to be substantially flat. This has advantages for compact storage, and the hose can easily be coiled or rolled, and the volume is significantly reduced. The ends of the sections of hose 42,44 are passed over cylindrical interface portions of the coupler and slid along until they abut against an annular shoulder having a greater diameter than the cylindrical interface portions. The sections of hose 42,44 are secured in place using fixing means 46,48. As can be seen, the fixing means 46,48 are adapter to be non- snagging; that are smooth annuluses and are flush with the annular shoulder of the coupler. This is advantageous as it reduces the risk of snags occurring during deployment or retrieval of the delivery device. A similar arrangement is used on all couplers and end caps and the like. The fixing means are suitably crimps which are well-known for securing and sealing hydraulic hoses. The coupler comprises an aperture 48 through which the treatment fluid can pass. Fig 8 shows a cross-section of coupler as set out in Fig 3, which is suitable for use with a 75mm hose. Like features are shown with the same reference number. However, this cross section reveals the additional apertures 48' orthogonal to the first aperture 48. Furthermore, the clamping surfaces 49 against which the hose is retained by crimps are show. Annular lips 47 are present at the end of each clamping surface which prevents the hose and crimp slipping off the coupler. Fig 4 shows a T-piece coupler 50 which couples a branch hose to the lateral hose. An aperture 54 is provided on the portion of the T-piece which descends into the water (the leg) which attaches to the branch hose. A float is attached to one of the arms cross-piece of the T-piece. The two arms of the cross-piece are different lengths. The arm on the right, as viewed in the figure, is longer than the left, and allows for the float to be slid over the cylindrical arm prior to attachment of the hose. Fig 10 shows a cross section of the T-piece and Fig 9 shows the leg piece. The threaded end 56 of leg piece screws into a

corresponding threaded aperture 58 on the cross-piece to form the complete T-piece.

Clamping surfaces 57 are shown against which the hose is crimped. The additional apertures 54' not visible in Fig 4 can be seen in Fog 10. On the cross-piece, a mounting surface 59about which the annular float is attached is shown, and the float is retained by retaining ring 53.

Figure 5 shows a coupler 60 in which a replaceable nozzle 62 has been installed. In one embodiment the couple comprises one or more threaded apertures 48 having a diameter of 12.25mm, into which a corresponding cylindrical threaded nozzle is screwed. In another embodiment the coupler 60 comprises an aperture through the annular shoulder. A shoulder (not shown) is provided at the inside of the aperture against which the nozzle 62 abuts and thus cannot pass completely through the aperture. The nozzle is retained in position by a retainer 64. The aperture is provided with a thread into which the retainer 64 screws and the nozzle is thereby sandwiched between the shoulder and the retainer 64. As discussed above, the nozzle can be removed and replaced with a different sized nozzle, and the flow rate through the installed nozzle can thereby be adjusted.

Figs 6a and 6b show one embodiment of an end cap system for the lateral hoses. Fig 12 shows a cross section of an end-piece as shown in Figs 6a and 6b. As can be seen, the lateral hose terminates with an end piece 72. The end piece comprises an interface portion onto which the end of the hose section is fixed using the fixing means in the manner described preciously in respect of the couplers 60. An end cap 70 is adapted to fit onto the open end of the end piece 72 and thereby seal the end of the hose. In the embodiment shown, the end piece is provided with a screw thread 75 onto which the end cap is screwed via corresponding thread 75'. An O-ring 74 is provided which is compressed between the end cap and an annular shoulder provided on the end-piece, thereby substantially hermetically sealing the end of the lateral hose. As can be seen in Fig 6, the end cap 70 comprises an attachment point 76 for attachment of a rope 78, in this case in the form of a metal loop to which the rope is attached (not shown in Fig 12). A revolute joint is preferably provided to allow the end cap to rotate without introducing twists into the rope, as this could lead to tangling. Having a rope attached to the end of the lateral hoses is very useful when deploying the delivery device as the lateral hoses can be pulled across the surface of an enclosure using the ropes.

Fig 7 shows an end piece 82 for the lower end of a branch hose 80. Fig 11 shows a cross section of an end-piece as shown in Fig 7. As can be seen, the end-piece 82 is provided as a one-piece construction with an integrated cap, in contrast to the 2-piece system used on the lateral hoses. In this case the end piece is formed from a piece of a polymeric material, such as high-density polyethylene (which can also be the material from which the couplers are formed). The end piece 82 is fitted to the end of the hose by the fixing means described above. An aperture 84 is provided in the side of the end piece, and another is provided in the middle of the cap. To facilitate the branch hose descending into the desired position, the end piece 82 can be provided with a weight 85, for example mounted in the body of the end- piece. Suitably this weight defines a nozzle. The 84 weight can suitably be threaded and inserted into a threated section of the end-piece.

The hose sections used in the delivery device can have different diameters, depending on the intended flow capacity of any the section of hose. Suitable diameters for the hoses are 75 mm and 125 mm, but other diameters can of course be used. It is advantageous to use narrower hoses where possible as this reduces the weight and cost of the delivery device, and allows for more compact storage. Couplers and end pieces will of course have to be adapted for the relevant hose diameters. In one example, the lateral hoses can have a larger diameter, e.g. 125 mm, than the branch hoses, e.g. 75mm. The lateral hoses typically have to carry more fluid than branch hoses because they supply several branch hoses. It will be appreciated that many permutations of different hose sections are possible. Where a wide hose, e.g. 125mm, is connected to a narrower hose, e.g. 75mm, some form of step- down means must be provided; this can be conveniently be achieved using the couplers to step-down the diameter, e.g. by having interface portions having different diameters.

Table 2 provides an example of a possible delivery device configuration, with the relevant aperture sizes. In this case the delivery device used a hose of 50mm diameter and all the nozzles were 8mm ID. This configuration was prepared as an initial proof of principle test. Table 2

However, it has been found that increasing the aperture diameter towards the distal ends of the delivery device (i.e. those apertures further from the inlet into the delivery device) helps to allow balanced deliver. This is largely because the increased aperture size compensates for pressure drop along the length of the hoses.

Fig 18 shows the distribution of various aperture sizes on the central portion of the delivery device of Fig 1. 8mm apertures 1 10 are used proximal to the inlet, then 10 mm apertures 1 12, followed by 12 mm apertures (1 14), and finally the most distal apertures are 13mm apertures 1 16.

A constrainer 90 according to the present invention is shown in Fig 13. The constrainer is a tarpaulin. It is pyramidal in form, and comprises a plurality of triangular panels 92, which are joined together via their edges 94 to form the pyramid shape. The panels are suitably made from a water proof fabric such as nylon, which can be coated to reduce permeability. The points of the pyramidal panels meet at the apex 96 of the pyramid. The bases of the triangles define the perimeter 100 of the constrainer. Reinforcement webbing straps pass around the perimeter 100 of the constrainer, and also along the joints between the edges 94 of the panels 92 and running down to the apex 96. The webbing straps reinforce the structure so that it can withstand the loads imparted during deployment, use and retrieval. On the perimeter of the constrainer 10, at the location joints between the panels, there are provided lifting/attachment points 98. Fig 14 shows another view of the constrainer 90. Figure 15 shows in more detail the perimeter of the constrainer. The reinforcing webbing strap 102 running around the perimeter 100 is shown. Another reinforcing webbing strap 104 runs down the panel joint to the apex. Further reinforcement panels 106 and 108 are provided to further reinforce this node. Panel 106 is coloured red, and panel 108 is coloured blue. This colour coding assists in the deployment and installation process. Metal eyes 108 are provided at the lifting/attachment points 98. A rope 1 10 is attached to the eye 108. In use, a weight (not shown) can be attached to the apex of the constrainer 96. An example of the deployment, use and retrieval of the treatment system of the present invention will now be described. In the present case the method is described as it would be applied to a typical salmon pen.

Two vessels are typically used to effectively deploy and install the tarpaulin. One is the 'workboat' carrying the tarpaulin and an oxygen delivery system. The other boat is the 'site boat', preferably with two capstans.

The workboat is positioned at the appropriate side of the enclosure which allows the tarpaulin to be deployed into the tide. This will ensure that the maximum amount of water enclosed in the tarpaulin for the treatment, i.e. that the tarpaulin is fully 'inflate' by the tide. The site boat is positioned directly opposite.

The net of the pen is lifted to reduce the volume of the enclosure, and thereby reduce the volume of water to be treated.

The present example relates to a typical 100m circumference salmon pen. However, the method of installation can easily be modified for other pen sizes, e.g. 120m circumference.

The enclosure has a number of vertical stanchions around the perimeter of the pen, in the present example there are 40 stanchions. Designating the stanchion next to where the tarpaulin is deployed by the workboat "0", we can work both directions round the pen identifying every fourth stanchion as the 4's, 8's, 12's, 16's and 20 stanchions and running a rope from the workboat to each of these. These ropes are attached to corresponding haul points on the tarpaulin (for a typical 120m pen there are additionally 2 x 20's and a 24 stanchions). The ropes from the 4's, 8's and 12's are taken back to the workboat. The 16's and 20's are run to the site boat, which is positioned diametrically opposite the workboat. There is also a rope used for pulling the tarpaulin into the water and recovering it after the treatment which is run from the workboat to the site boat under the net of the pen; this is referred to as the 'recovery rope'. This recovery rope is connected to the apex of the tarpaulin, where a weight is also attached; the weight acts to help the apex of the tarpaulin descent into the water and to hold it in the desired cylindrical/conical conformation.

Once all the stanchion ropes are in place the tarpaulin is deployed by tying the "recovery rope" onto the ring next to the weight on the apex of the tarpaulin. The site boat then winches the recovery rope which pulls the tarpaulin into the water under the net of the pen. The weight causes the apex to sink into the water.

Securing the rope at the "0" position haul point of the tarp at the stanchion next to the workboat, the tarp is completely released from the crane on the workboat and the recovery rope is given a last pull to get the tarp into the water. The workboat winches the ropes running though the 4's then 8's then 12's to haul the respective haul points tarpaulin into position. The site boat then winches the ropes for the 16's then the 20.

In the case of a 100m tarp, weights are tied to the haul points on the tarpaulin corresponding to the 16's and 20 (on the 120m tarp the weights go on the 20's and 24). The weights serve to keep the tarpaulin Open' to facilitate complete filling as it is winched into the tide by the site boat - this is a significant advantage of the present design as it ensures that the tarpaulin is completely filled, and thus the treatment volume is as intended, allowing accurate dosing.

The additional tarp positions, i.e. corresponding to the intermediate stanchions between the multiples of 4, are pulled up by hand and tied off ensuring the perimeter of the tarpaulin is clear of the water.

When this is complete, the treatment is ready to begin. The weights attached to the 16's and 20 points on the tarpaulin are removed and put on the site boat and all winching ropes coiled onto the appropriate boat.

The recovery rope is taken from the site boat back to the workboat in preparation for recovering the tarpaulin after the treatment. The site boat is now free to move onto the next pen in the farm to lift the net.

The delivery system is then deployed. The delivery system is typically stored wound around a drum. Ropes connected to the end pieces of the lateral hoses are used to draw the lateral hoses across the top of the pen. The branch hoses sink into the water beneath the lateral hoses. The ropes are tied off to secure the lateral hoses in position.

The work boat also deploys an oxygen delivery system, which is used to maintain oxygen levels within the constrained volume. An option in the present invention is to combine oxygen delivery with hydrogen peroxide delivery through the delivery system.

The treatment agent is then delivered. This is achieved by pumping a fluid containing the treatment agent into the delivery device. Suitable pumping apparatus are well known in the art. A particularly suitable apparatus is described in UK patent application no GB1304148.8. Once the appropriate dosage has been delivered, the pumping process is stopped.

It is advantageous of the treatment agent is diluted prior to it being delivered to the volume of water to be treated, as discussed previously. It can be preferred that water is withdrawn from the volume of water to be treated and then used to dilute the treatment agent. This means that the volume of water within the constrainer is maintained essentially constant as the water used for dilution originates from within the constrainer rather than being obtained from outside and added into the constrained volume. However, it has been found that this is unnecessary and, given the relative volumes of the constrained volume and the amount of water used to dilute the treatment agent, it is perfectly satisfactory and simpler in many ways to collect dilution water from outside of the constrained volume.

The delivery device is suitably fed by three pumps, one for the treatment agent and two for seawater. Table 3 shows pumping rated for 3 exemplary pumps.

Table 3

Delivery of the treatment can be carried out to maximise the rate of delivery of the treatment agent, e.g. as shown Table 4. In all the examples discussed, the source of H₂0₂ is a bulk store of 50% by volume H₂0₂ in water.

Table 4 Calculation based on dose and full pump capacity (Quickest dose rate)

Dose (H202) 5000

Time (mins) 2.50

Dilution 12.50%

Seawater (litres) H₂0₂ (litres) H₂0₂ (100%) Water

Pump 1 0 5000 2500 2500

Pump 2 10000 0 0

Pump 3 10000 0 0

Total 20000 5000 2500 2500

Delivery can be slowed down to some extent in order to achieve higher dilution of the treatment agent, e.g. as shown in Table 5. In this case the amount of 50% H₂0₂ delivered is the same, but it is delivered at a slower rate, while the delivery of seawater is delivered at the same rate as in Table 4 - this results in greater dilution during the delivery phase.

Increased dilution during delivery is a highly desirable property of the present invention, especially for a treatment agent which can be harmful at high concentrations, such as H₂0₂.

Table 5

Figs 16 and 17 give exemplary delivery protocols for various constrainers and pen configurations for delivering 50% by volume H₂0₂. It is well within the skilled person's routine ability to modify such protocols for other agent/pen types/delivery strategies.

When the treatment is complete, starting opposite the workboat and working towards it, the tarpaulin ropes can be released while the recovery rope is winched. This inverts and empties the tarpaulin as the apex is raised to the surface. The crane is then used to recover the tarpaulin from the water to the deck of the workboat. The oxygen and chemical dosing system can now be removed from the pen and the net dropped back into its normal position.

In a variation of the present invention, the constrainer can be provided with a system to allow for the volume of the constrainer to be modified. For example, where the biomass to be treated is lower than usual, it may be desirable to reduce the volume of the constrainer to avoid the need to use excess treatment agent. This can conveniently be achieved through the provision of a system to pull the conical or pyramidal constrainer tight to form a secondary apex at a shallower level; this will result in a constrainer with the same diameter, but a shallower depth and less steeply sloped sides. This can be achieved, for example, by providing a draw-cord running around the circumference of the constrainer at an

intermediate position between the apex and the perimeter, for example at a location approximately one third of the total depth of the constrainer from the 'true' or 'primary' apex. The draw-cord can suitably run through a number of runners (e.g. eyelets) on the outer or inner surface of the constrainer. Preferably the draw-cord does not require any holes through the constrainer, which would allow water to pass through them. When the draw- cord is pulled tight, the constrainer is pulled tight and a secondary apex is formed. Excess fabric simply folds upon itself. This simple, yet effective, system allows for the volume of the constrainer to be adjusted before or after installation at the pen. If adjustment occurs after installation, displaced water can flow over the top of the perimeter, or an opening (e.g. a sealable flap or the like) can be provided in the constrainer to allow the water to pass out. It is typically preferred that adjustment is made prior to completion of installation of the constrainer at a pen. Another variant of the present invention allows for additional water to be forced into the constrainer to ensure it is completely filled. It has been described above how the installation procedure is adapted to ensure complete filling during installation. However, it is possible that, in some cases filling may not be perfect (e.g. following an unexpected change in sea conditions or an error in the installation process). The constrainer can be provided with an air lift pump to deliver water into the interior volume of the constrainer. Conveniently this can be located at or near the apex of the constrainer. Air lift is an extremely efficient mechanism to facilitate movement of water in an upwards direction, and is well known in the art. All that is required is a riser tube and an air compressor to provide air to be entrained in the water, thereby reducing its density and inducing it to rise into the constrainer. Accordingly, a constrainer fitted with such an air lift system can be topped up with water if required.

Benefits of the constrainer of the present invention include: - Predictable and consistent volumes due to the design. This is key to successful and safe treatments.

- Ease of deploying and installation. (Rapid removal once treatment is complete is

advantageous to fish health).

- Ease of removing tarpaulin with a quick turnaround for deploying in the next pen.

- Increased number of treatments completed per day.

- Able to move from one location to another quickly.

- Reduced fish stress.

- Can be used in all current conditions and the design allows weighting that assists in holding the shape and volume if required, which results in less distortion.

- Strength due to shape and design.

- It allows heavier materials to be used, resulting in a stronger more reliable system but without the bulk and weight of previous designs.

- A reduced tarp volume enables the use of a significantly reduced volume of treatment agent.

- Can be easily adapted for all circular or polygonal pen sizes and designs.

- Easily disinfected.

- Ease of use means the fish/nets can be treated in situ hence reduced costs and improve conditions for the fish and reduce the likelihood of disease occurring.

- Cost savings due to the reduction in stress which allows less starvation days pre- treatment (1 day); a well boat treatment requires a minimum of 5 days starvation.

- Quicker return to previous feeding levels.

- Reduced mortality.

- Significantly reduced external influences, such as tide and wind.

- User friendly, easy to train staff in use.

- Ability to vary the volume of the tarp to suit the biomass to be treated. This system allows the volume to be altered both before deployment and also after it has been installed.

- System to aid the installation using air-lift to top up the constrainer. Benefits associated with the treatment agent delivery device include:

- Improved distribution of treatment agent and reduced risk of hotspots.

- Efficient Distribution / High volume dilution capacity.

- Snag free and user friendly.

- Can be balanced to match different dosing systems and volumes by changing the

apertures/hole sizes. - Easy to deploy and retrieve. Can be used in conjunction with a pipe reel for the convenient deployment and storage.

- Reliability and reduced service costs.

- Easily disinfected.

- More accurate dosing with regards to treatment concentration. Achieves effective concentration rapidly throughout the treatment volume.

- Reduced treatments costs due to accurate dosing and the requirement for follow up treatments.

- Reduction in mortality.

- Reduction in repeat treatments and resistance to products.

- Assists in staff focusing on importance of deployment and set up. Allows SOP to be drawn up and followed.

Claims

- a constrainer formed from flexible sheet material, the constrainer having a

generally conical or pyramidal form, the constrainer being adapted to surround a enclosure containing organisms to be treated, and

- a treatment fluid delivery device comprising at least one hose, the hose comprising a plurality of apertures along its length to allow the treatment fluid to exit therethrough.

The system of claim 1 further comprising a pump apparatus adapted to pump a treatment fluid into the delivery device.

The system of claim 1 or 2 wherein the volume constrained by the constrainer is from 500 to 36,000 cubic meters.

The system of any preceding claim wherein the constrainer comprises a plurality of panels which are joined together.

The system of any preceding claim wherein the constrainer comprises reinforcing strips, arranged to align with the main forces applied to the constrainer during installation and/or removal, or when deployed.

The system of any preceding claim wherein there is a substantially continuous stretch of webbing around the perimeter of the constrainer.

The system of any preceding claim wherein lengths of webbing run from lifting/haul points on the perimeter of the constrainer to the apex.

The system of any preceding claim wherein the constrainer is formed from a plurality of triangular panels joined to form a pyramid, each triangular panel defining one face of the pyramid.

The system of any preceding claim wherein the constrainer is adapted to facilitate weighting of the apex in use or wherein the constrainer has a weight associated with the apex.

10. The system of any preceding claim wherein the constrainer is provided with a plurality of attachment points along its perimeter.

11. The system of any claim 5 wherein the reinforcing straps continue below the apex to form a plurality of loops.

12. The system of any preceding claim wherein the constrainer is provided with a system to allow for the volume of the constrainer to be modified.

13. The system of any preceding claim which comprises a pump to fill the constrainer with water.

14. The system of claim 13 wherein the pump comprises and air lift pump.

15. The system of any preceding claim wherein the constrainer is provided with buoyant means at least a portion of the perimeter.

16. The system of any preceding claim wherein the delivery device consists of at least one lateral hose adapted to extend across the surface of the volume of water to which a treatment agent is to be delivered, and at least one branch hose connected to said lateral hose adapted to extend downwards into the volume of water to be treated.

17. The system of claim 16 wherein the delivery device comprises a plurality of lateral hoses adapted to extend across the surface of the volume of water, with each lateral hose comprising at least one branch hose.

18. The system of claim 16 or 17 wherein at least one lateral hose is adapted to be

buoyant during use such that it floats at the surface of the volume of water to be treated.

19. The system of any one of claims 16 to 18 wherein at least one branch hose, preferably all branch hoses, is/are adapted to be negatively buoyant so that they sink into the volume of water to be treated.

20. The system of any one of claims 16 to 19 in which the delivery device comprises: - a feed conduit adapted to connected to a source for supplying the treatment fluid under pressure;

- a splitter to split the fluid flow from the feed conduit into a plurality of lateral hoses adapted to be deployed in parallel across the surface of the treatment volume; - each lateral hose being provided with a plurality of branch hoses adapted to extend downwards into the treatment volume when the device is deployed.

21. The system of any one of claims 16 to 20 wherein the diameter of the hoses is varied within the delivery device.

22. The system of any one of claims 16 to 21 wherein the apertures comprise nozzles to modify the flow of fluid through the apertures.

23. The system of any one of claims 16 to 22 wherein the delivery device comprises one or more collars which are provided with apertures through which the treatment fluid flows.

24. The system of claim 23 wherein the collars comprise a cylindrical body, the wall of which comprises one or more apertures.

25. The system of any one of claims 16 to 24 wherein the apertures comprise removable nozzles.

26. The system of claims 25 wherein the nozzles are removably mounted in a bore

through the wall of a collar.

27. The system of any one of claims 16 to 26 wherein the delivery device comprises a plurality of apertures, some of which have different flow rates from others. 28. The system of any one of claims 16 to 27 wherein the delivery device comprises a plurality of sections of hose joined by coupling members, the coupling members being adapted to allow flow between the sections of hose.

29. The system of any one of claims 16 to 28 wherein the couplers comprise apertures for delivery of the treatment fluid.

30. The system of any one of claims 16 to 29 wherein the delivery device comprises a least one linear coupler comprising a generally cylindrical body, the body having an annular shoulder projecting outward from the body approximately at its middle, the annular shoulder having a larger external diameter than the cylindrical portions to either side of it, the cylindrical portions either side of the annular shoulder defining interface portions adapted to slide into the end of the hose sections.

31. The system of any one of claims 16 to 30 wherein the delivery device it is free from potential snag points.

32. The system of any one of claims 16 to 31 wherein the delivery device comprises a collapsible hose.

33. A constrainer formed from flexible sheet material, and having a generally conical or pyramidal form, the constrainer being adapted to enclose an aquaculture enclosure containing organisms to be treated.

34. A treatment fluid delivery device for an aquaculture enclosure comprising at least one hose, the hose comprising a plurality of apertures along its length to allow the treatment fluid to exit therethrough. 35. A method of preparing an aquaculture enclosure situated in a body of water to facilitate administration of a treatment agent, the method comprising:

- providing a constrainer formed from flexible sheet material, and having a generally conical or pyramidal form, the constrainer being adapted to enclose an enclosure containing organisms to be treated;

- enclosing said enclosure with the constrainer and thereby isolate the constrained volume of water from the larger body of water in which the enclosure is situated;

- providing a treatment fluid delivery device comprising at least one hose, the hose comprising a plurality of apertures along its length to allow the treatment fluid to exit therethrough; and

36. The method of claim 35 which comprises weighting the constrainer to promote

adoption of the intended conformation. 37. The method of claim 35 or 36 which comprises delivering the treatment agent to the constrained volume of water.

38. The method of claim 37 wherein the treatment agent is hydrogen peroxide.

39. The method of claim 37 wherein the hydrogen peroxide is diluted from a concentrated form to a diluted form prior to passage from the delivery device to the volume of water to be treated.

40. The method of any one of claims 35 to 39 comprising oxygenating the volume of water to be treated.

41. A method of isolating an aquaculture enclosure from the body of water in which it is situated, the method comprising:

- providing a constrainer formed from flexible sheet material, and having a generally conical or pyramidal form, the constrainer being adapted to enclose an enclosure containing organisms to be treated; and

- enclosing said aquaculture enclosure with the constrainer and thereby isolate the constrained volume of water from the larger body of water in which the enclosure is situated.

42. The method of claim 41 which comprises installing the constrainer against a tidal flow. 43. The method of claim 41 or 42 which comprises providing a weight on the apex of the constrainer.

44. The method of any one of claims 41 to 43 which comprises providing one or more weights on the perimeter of the constrainer to ensure that the perimeter of the constrainer sinks into the body of water and thereby allow water to enter the constrainer.

45. The method of any one of claims 41 to 44 which comprises the step of retrieving the constrainer, wherein retrieval comprises hauling on the apex of the constrainer to cause the constrainer to empty as it is hauled.

46. A method of treating a volume of water with a treatment fluid, the method comprising:

- providing a treatment fluid delivery device comprising at least one hose, the hose comprising a plurality of apertures along its length to allow the treatment fluid to exit therethrough;

- deploying the treatment agent delivery device into the volume of water; and

- delivering the treatment fluid to the volume of water.