GB2302525A

GB2302525A - Submersible Platform for fish-farming.

Info

Publication number: GB2302525A
Application number: GB9613075A
Authority: GB
Inventors: Nigel Burgess
Original assignee: SUBSEA SHELLFISH Ltd
Current assignee: SUBSEA SHELLFISH Ltd
Priority date: 1995-06-23
Filing date: 1996-06-21
Publication date: 1997-01-22
Anticipated expiration: 2016-06-21
Also published as: GB9512886D0; GB9613075D0; GB2302525B

Abstract

A submersible fish-farming platform 5a, particularly for shellfish such as mussels, oysters, scallops and like marine molluscs, comprises a frame having one or more chambers 40a of adjustable buoyancy retained in association therewith, the frame further having means for retaining fish stocking means therebelow, the platform being adapted to be submersible to a chosen depth and retained substantially thereat by means of the one or more chambers. Buoyancy control is by way of air supply via valve 70a which controls the amount of water entering the bottom of chamber 40a. The shellfish may be suspended in lantern nets (250b, Fig 3) or attached to ropes. The platform has a permanent buoyancy hose 30a sufficient to maintain the platform on the surface for maintenance or husbandry purposes. Access to the platform is via a walkway 110a. Means may be provided to improve the flow of nutriet / plankton rich water to shellfish stock suspended from the platform (Figs 17-21). An incubator may be provided within the adjustable buoyancy chamber to improve the food supply available to the stock.

Description

Submersible Platform and Related Method This invention relates to a submersible platform and related method for use in fish-farming and particularly, though not exclusively, the farming of shellfish such as mussels, oysters, scallops and like marine molluscs.

Presently known apparatus employed in shellfish farming suffer from a variety of problems. For example, predation, surface motion, overcrowding of sea loches, visual impact, equipment failure and safety.

It is, therefore, an object of at least one aspect of the present invention to obviate one or more of the aforementioned problems in the prior art.

According to a first aspect of the invention there is provided a submersible fish-farming platform comprising a frame having one or more chambers of adjustable buoyancy retained in association therewith, the frame further having means for retaining fish stocking means therebelow, the platform being adapted to be submersible to a chosen depth and retained substantially thereat by means of the one or more chambers.

The platform is particularly suitable for farming shellfish. The fish stocking means may, therefore, comprise ropes in the case of, for example, mussels, or lantern nets in the case of, for example, scallops.

Preferably there is also provided one or more reserve buoyancy chambers which, in use, are located at the surface and connected to the platform by a flexible connection(s) such as a chain(s) or pipe(s).

In one embodiment of the invention the frame is substantially circular in shape, the frame comprising a peripheral member and a hub, a plurality of spokes extending between the hub and the peripheral member.

Adjacent spokes may have the retaining means comprising a plurality of wires extending therebetween.

There may be at least one chamber of adjustable buoyancy which in said one embodiment may be substantially at the centre of the frame, which may be of cylindrical shape, and which may have an open base.

Preferably also the shellfish supporting ropes/lantern nets may be suspended from frames supported between the spokes of the platform.

The frames may be configured in a rigid lattice arrangement or made from netting strung between a rigid parameter depending on the shellfish to be supported.

In another embodiment of the invention the frame is substantially rectangular in shape. In this embodiment, the retaining means may comprise a plurality of wires extending between first and second substantially parallel sides of the frame.

The platform may also provide a walkway moveable over the retaining means.

The platform may also be provided with permanent buoyancy means.

The platform may also include means to improve the food supply available to the stock by providing an environment conducive to the production of algae/phytoplankton.

Such an environment may be provided by an incubator provided within the at least one chamber of adjustable buoyancy, said chamber having an aperture, said incubator comprising an ultraviolet light source, means for heating the water contained within the chamber and insulating means.

Said aperture may be formed in the base of said chamber.

Energy for the light source and heating means may be provided by wind or wave power generation or any other suitable means.

The platform may be provided with means to improve the flow of nutrient/plankton rich water to shellfish stock suspended from said platform.

According to a second aspect of the invention there is provided a method of fish-farming comprising submerging a platform to a chosen depth and retaining same substantially thereat, the platform comprising a frame having one or more chambers of adjustable buoyancy retained in association therewith, the frame further having means for retaining fish stocking means therebelow, the platform being retained at the chosen depth by means or the one or more chambers.

According to a third aspect of the present invention there is provided a fish-farming platform comprising a frame having one or more buoyant chambers retained in association therewith, the frame further having means for retaining fish stocking means therebelow, the retaining means comprising one or more wires extending at least partially across the frame such that fish stocking means, such as ropes or lantern nets, may be hung therefrom.

According to a fourth aspect of the present invention there is provided a fish-farming platform having fish stocking means and including circulation apparatus adapted to provide flow of nutrients/plankton rich water to the fish stocking means.

Preferably the fish stocks may be shellfish.

Preferably also the fish farming platform may be wholly or at least partially submersible.

The means may comprise the redirection of water from or near the surface of the body of water in which the platform is located to a position at or below the lowermost shellfish stocks suspended from the platform.

The means may also comprise the rotation of the platform as a whole.

Said means may utilise wave, wind or tidal power, or any combination of the three.

The means may comprise a plurality of sails intended to impart rotational motion to the platform when acted upon by tidal current flow.

The sails may further serve to direct water captured by the sails towards the shellfish stocks.

Alternatively the means to improve the flow of nutrient/plankton rich water to shellfish stocks may comprise at least one pump located within the platform, said pump having at least one inlet and an outlet, and means to drive said pump.

The pump may be driven by energy derived from either a wind turbine or by wave motion.

The pump may take the form of a shaft driven low head/high volume type pump.

Alternatively the pump may take the form of a buoyant spool which is free to oscillate under wave motion.

According to a fifth aspect of the present invention there is provided circulation apparatus adapted to provide flow of nutrient/plankton rich water to fish stocking means of a fish-farming platform.

Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings which are: Fig 1 a side view of a first embodiment of a platform according to the present invention; Fig 2 a plan view of the platform of Fig 1; Fig 3 a perspective view of a second embodiment of a platform according to the present invention, which shows the equipment needed to stock/harvest the platform; Fig 4 a plan view of the platform of Fig 3; Fig 5 a side elevation of the platform of Fig 3; Fig 6 a plan view of an embodiment of a tray used to support shellfish ropes/lantern nets for use with a platform according to the present invention.

Fig 7 a plan view of a third embodiment of a platform according to the present invention; Fig 8 a view of a longer side of the platform of Fig 7; Fig 9 a view of a shorter side of the platform of Fig 7; Figs 10 (a)-(d) a series of side views of the platform of Fig 7 showing the platform being submersed in use; Fig 11 an enlarged view of a portion of the platform of Fig 7, when the platform is on the surface; Fig 12 an enlarged view of a portion of the platform of Fig 7, when the platform is below the surface; Figs 13 (a)-(b) a first mooring arrangement for the platform of Fig 7; Fig 14 a second mooring arrangement for the platform of Fig 7; Fig 15 an enlarged view of another portion of the platform of Fig 7; Fig 16 a plan view of the platform of Fig 7.

Fig 17 a plan view of a fourth embodiment of a platform according to the present invention incorporating a tidal powered circulating system; Fig 18 a side view of the platform of Fig 17; Fig 19 a plan view of a rope arrangement for the platform of Fig 17; Fig 20 a perspective view of a fifth embodiment of a platform according to the present invention incorporating a wind powered circulating system; Fig 21 a partially cut-away view of a wind powered pump apparatus for the platform of Fig 20; and Figs 22a-22c a series of side views of a wave-powered pump for use in conjunction with a platform according with the present invention.

Referring to Figs 1 to 16 there are provided first, second and third embodiments of submersible shellfish growing platforms according to the present invention, generally designated 5a, 25b and 35c.

The platforms 5a, 25b and 35c enable a shellfish grower to keep shellfish stock at a constant depth, eg 2 to lOm, below surface. At such a depth, the equipment and stock is out of damaging surface wind and wave action, and yet also clear of the seabed and bottom dwelling predators.

Referring to Fig 1 the shellfish platform 5a is maintained at a fixed depth by a large buoy 40a which provides sufficient reserve buoyancy for the platform 5a plus the on-growing weight of stock.

Reserve buoy 10a is in turn attached to a single mooring buoy 20a, serving a 3 leg swinging mooring.

The platform 5a has permanent buoyancy in a perimeter hose, 30a which is sufficient to maintain the platform 5a on the surface. The hose 30a is closed on itself, forming a circular frame shape.

Adjustable buoyancy for the growing stock is provided by an open bottomed, cylindrical chamber 40a mounted with its centre axis vertical. Steel radial spokes 50a connect the perimeter hose 30a to the central chamber 40a. Steel cables 60a to which the growing stock is attached intersect with the spokes 50a, so that in plan view the structure has the appearance of a spiders web. The growing stock may be attached by means of ropes, for example at 0.5m intervals in the case of mussels, or lantern nets, for example, at im intervals in the case of scallops.

Buoyancy control is by means of an air activated valve 70a which is normally in the closed position. A hose 31a for filling and operating terminate in a manifold 90a attached to the reserve buoyancy 10a. To submerge the platform 5a, the operating line is pressurised, opening the valve 70a at the top of the buoyancy chamber 40a, and venting air to allow water into the bottom of the chamber 40a. When the platform 5a submerges the operating line is depressurised, closing the top valve 90a. The platform 5a now hangs down on the reserve buoyancy 10a and can be monitored for on-growing weight of stock by draught marks on the reserve buoy 10a. When, for example, 75% of the reserve buoyancy l0a is immersed an operator will supply air into the chamber 40a.

When maintenance or husbandry is to be carried out, the platform 5a can be raised to the surface by injecting sufficient air to lift the whole platform 5a to the surface.

This operation should be carried out when there is a good, sufficient tidal current to keep the platform 5a downstream of the mooring buoy 20a and service craft 100a.

Access to the platform 5a is provided by a radial walkway l10a which rotates about the central buoyancy chamber 40a. The outer end of the walkway ll0a has a trolley mounting 120a onto the perimeter hose 30a, which allows the services craft 100a to berth alongside.

Harvesting can be carried out by transferring stock to the service craft 100a or by lifting tackle fitted directly to the walkway 110a.

Referring now to Figs 3 to 5 there is shown a submersible platform 25b comprising a substantially cylindrical central structure 210b, and a circular frame 215b. The frame 215b comprises a plurality of radially extending rigid spokes 220b and a permanently buoyant peripheral member 225b. The central structure 210b further comprises a chamber of adjustable buoyancy 230b, the lower portion 235b of which is open to the water, and a mast 240b.

The central structure 210b and peripheral member 225b exhibit sufficient permanent buoyancy to maintain the unladen platform 25b on the surface, while the frame 215b is free to rotate about the central structure 210b under the influence of wind, wave and tidal conditions. Shellfish may be attached to trays 245b, which in turn are suspended between the spokes 220b of the frame 215b. The shellfish may be suspended in lantern nets 250b, or attached to ropes (not shown).

In use, the platform 25b is towed to its intended site and moored by at least three rising anchors 252b. The platform 25b may then be stocked as follows: trays 245b are loaded with shellfish stock and transported to the moored platform 25b by a harvesting vessel 255b. An embodiment of such a vessel 255b is shown in Figure 1 and comprises a pair or hulls 260b, a deployable skip 265b provided therebetween, winch means 270b to raise and lower said skip 26 5b, and winch means 275b to aid in the transport of a tray 245b from the harvesting vessel 255b to the platform 25b. The harvesting vessel 255b, is moved into contact with the frame peripheral member 225b and secured by means of a docking clamp (not shown). A tray 245b can then be transferred to the platform 25b by two lines 280b, 285b which are passed below the peripheral member 225b.The first line 280b is threaded through a pulley 290b, provided on the mast 240b, and down to a winch 295b positioned at the base of the mast 240b. The tray 245b can then be lowered beneath the harvesting vessel 255b and simultaneously lifted by the mast winch 295b. The second line 285b is used to guide the tray 245b into position between the spokes 220b. Once the tray 245b is in position the first line 280b is secured by a ratchet strap 297b to prevent it from working loose, while the second line 285b is released from the harvesting vessel 255b with a small float attached (not shown). The operation can be repeated until the platform 25b is fully stocked with shellfish.

Once fully stocked, the platform 25b can be submerged to the required depth for shellfish growth by allowing air to be vented from the adjustable buoyancy chamber 230b. The resulting ingress of water into said chamber 230b through its open end 235b reduces the overall buoyancy of the platform 25b and hence causes it to submerge. The vent valve (not shown) may be positioned atop the mast 240b allowing it to be operated from a service craft. Once the platform 25b reaches the required depth below the surface the vent valve is closed. The mast 240b may also be provided with draught markings 298b which can be used to indicate the weight of the growing shellfish stock.

In order to harvest the shellfish stock from the platform 25b, or to inspect/maintain the stock, the platform 25b must be raised to the surface. This is accomplished by the introduction of compressed gas into the adjustable buoyancy chamber 230b. Means for introducing gas into the chamber 230b may be provided in the mast 240b and comprise a compressed gas storage cannister and a supply valve, said valve being operable from a service craft. Such an arrangement of cannister and valve may be automated to maintain the submerged platforms 25b at the correct depth.

As the weight of the shellfish stock increases, the platform 25b is inclined to sink lower below the surface. An automatic control system, responsive to the depth of the platform 25b, may be used in conjunction with the gas cannister and valve to offset the sinking of the platform 25b.

At harvest time, the trays 245b are removed as follows.

When the stock is due for harvesting, the platform 25b is raised to the surface by injecting gas into the adjustable buoyancy chamber 230b. The harvesting vessel 255b is berthed bow onto the platform 25b facing up wind/tide and docked onto the perimeter hose 225b. A gangway 296b can be lowered to the central platform to allow personnel to transfer. The harvesting skip 265b is lowered with curtain debris net hanked to sides and back. The securing line for the harvesting tray is now released from the toe rail, and the buoyed lifting line picked up by the harvesting vessel 255b. The tray is now released from the platform by the use of a pinch bar bearing between the top of the segment tray 245b and a fulcrum bar. When the tray 245b comes free from the platform 25b, it is lifted into position over the skip 265b and inside debris net.The harvesting skip 265b can now be mechanically raised to gather up the stock. The whole basket and tray remain slung between the hulls and are transported ashore for processing.

The platform 25b may be further provided with means to improve the available food supply to the growing shellfish and thus reduce the length of the growth cycle. The inside of the adjustable buoyancy chamber 230b is provided with a W light source, heating elements and insulating means. The combination of heat and light combines to promote the growth of algae, which in turn provide foodstuff for the shellfish.

The power for the light source and heating elements may be provided by a wind turbine placed atop the mast 240b, or by a damper piston arrangement present upon the platform 25b which converts wave motion to electrical power.

The embodiment shown in Fig 7 is similar in construction to that of Fig 1 except that the perimeter hose 30a is replaced by a plurality of adjacent elongate floats 330c which form a rectangular frame shape. Steel cables 360c, therefore, extend across the frame so formed, a walkway 396c being slidable along the frame to allow access.

Studies of raft culture growth rates have shown that normal stocking densities prohibit optimum growth of the shellfish stock. For example growth rates of shellfish stock upon platforms moored in locations where tidal currents are low may be as little as 15% of the optimum rate. Thus site selection has been a limiting factor for traditional raft systems. Although the present invention is designed for use in previously unsuitable locations it has been noted from tidal data that minimum water velocities required for shellfish stock growth are experienced for only 75% of the time. Furthermore the shellfish stock experiences little or no phytoplankton replenishment at slack water.

Referring to Figs 17 and 18 there is shown a submersible platform 25d in accordance with an aspect of the present invention adapted to improve water flow to the shellfish stock. The platform 25d is provided with a second permanently buoyant peripheral member 400d above the first peripheral member 225d. Held between said peripheral members 400d, 225d and the central structure of the platform 25d are three sails 405d, the geometry and position of which promote rotation A of the platform 25d about a central mooring swivel under tidal current flow B.

In addition to promoting rotation of the platform 25d, the sails 405d serve to funnel water towards the central structure 210d of the platform 25d. At the point where the sails 405d meet the central structure 210d of the platform there are provided ducts 410d which direct nutrient/plankton rich water captured by the sails 405d down towards the lowest levels of the shellfish stock. Salinity and temperature gradients ensure that this water is transported back towards the surface and hence comes into contact with all the shellfish stock.

Fig 19 shows an arrangement of ropes 415d from which the shellfish stock may be suspended. The arrangement may be likened to the vanes of an axial flow pump.

Figs 20 and 21 show a platform 25e in accordance with an aspect of the present invention incorporating wind powered means 420e to improve water flow to the shellfish stock. The central structure 210e of the platform 25e is surmounted by a wind turbine 425e which is connected via suitable gearbox means (not shown) and a drive shaft 430e to a pump 435e provided within the central structure 210e. A pipe 440e extends downwards from the central structure 210e to a point at or below the depth of the lowest level of shellfish stock. The pipe 440e is fitted at its lowermost end with a diffuser 445e.

Rotation of the wind turbine 425e, and hence the drive shaft 430e and pump 435e, causes water to be drawn into the central structure 210e through ports 450e provided in the hull of the central structure 210e below the water-line.

The water is then pumped down the pipe 440e and out through the diffuser 445e. Salinity and temperature gradients carry the nutrient rich water back to the surface past the shellfish stock. Replenishment of the surface water requires minimal tidal velocity to avoid recirculating stale water.

In addition to driving the pump 435e the wind turbine 425e may be utilised to generate electrical power for use in providing, for example, illumination or a radio link to the shore. In order to minimise the shear forces experienced by the plankton/nutrient rich water the pump 435e may preferably be of the low head/high volume type.

Referring finally to Figs 22a to 22c there is shown a wave powered pump 455f for use in conjunction with a platform according to an aspect of the present invention.

The pump 455f comprises a cylindrical mast 240f extending both above and below the water-line and which is provided within the central structure 210f of the platform. Within the mast 240f there is provided coaxially with the mast 240f a pipe 440f and a float member 460f, said float member 460f being free to travel relative to the pipe 440f and the mast 240f. The float member 460f takes the form of a spool with a lower float body 465f, an upper disc member 470f and a port 475f in the stem of the spool. The float body 465f and disc member 470f are toleranced such that the float member 460f may move freely along the pipe 440f while providing a degree of sealing to the space 480f provided between the float member 460f and the mast 240f.The mast 240f is further provided with inlet ports 485f and a shroud 490f incorporating a non-return valve system 495f. The pipe 440f is provided with ports 500f to allow fluid communication between the annular space 480f provided between the mast 240f and the pipe 440f, and the interior of the pipe 440f.

The wave pump 455f exploits the low motion response of the platform once it is submerged by allowing the float member 460f to oscillate freely under wave motion relative to the mast 240f and pipe 440f. The trough of a wave 505f causes water to be drawn through the non-return valve system 495f and into the mast 240f via the inlet ports 485f. Water drawn in thus is held in the space 480f defined between the float member 460f and the mast 240f. The rising crest of a wave 510f causes the float member 460f to rise and with it is carried the water held the space 480f. When the pipe and float member stem ports 475f, 500f align the water is transferred to the interior of the pipe 440f and subsequently discharged at or below the lowermost shellfish stocks.As before salinity and temperature gradients combine to transport the water back towards the surface.

Ideal wave characteristics take the form of a long swell attenuated by a long fetch, and such conditions are commonly found where submersible platforms are sited.

The embodiments of the invention described hereinbefore are given by way of example only and are not meant to limit the scope of the invention in any way. It will be apparent to a person skilled in this particular art that at least some embodiments of the present invention provide the following advantages over the known art: Improved growth rates; Safe working environment meets with new HSE requirements; Increased production by reduced stock disturbance; Minimum visual impact in sensitive environments; Reduces personnel time spent on the water; Easy handling of stock at harvest, increasing yield per man hour; Reduction in stock lost at harvest; Protection from surface and seabed predators; Even stock growth; Stock and equipment free of damaging wind/wave action; Low maintenance; Cost effective; and Useful for all types of shellfish.

Claims

1. A submersible fish-farming platform comprising a frame having one or more chambers of adjustable buoyancy retained in association therewith, the frame further having means for retaining fish stocking means therebelow, the platform being adapted to be submersible to a chosen depth and retained substantially thereat by means of the one or more chambers.

2. A platform as claimed in claim 1, wherein the platform is adapted for stocking of shellfish, the fish stocking means preferably comprising ropes in the case of, for example, mussels, or lantern nets in the case of, for example, scallops.

3. A platform as claimed in any preceding claim, wherein there is also provided one or more reserve buoyancy chambers which, in use, are preferably located at the surface and connected to the platform by a flexible connection(s) such as a chain(s) or pipe(s).

4. A platform as claimed in any preceding claim, wherein the frame is substantially circular in shape, the frame comprising a peripheral member and a hub, a plurality of spokes extending between the hub and the peripheral member.

5. A platform as claimed in claim 4, wherein adjacent spokes of the frame have the retaining means comprising a plurality of wires extending therebetween.

6. A platform as claimed in either of claims 4 or 5, wherein one chamber of adjustable buoyancy is provided substantially at the centre of the frame, which is of cylindrical shape, and which has an open base.

7. A platform as claimed in claim 4, wherein the fish stocking means are suspended from frames supported between the spokes of the platform.

8. A platform as claimed in claim 7, wherein the frames are configured in a rigid lattice arrangement or are made from netting strung between a rigid parameter depending on the shellfish to be supported.

9. A platform as claimed in claims 1 to 3, wherein the frame is substantially rectangular in shape.

10. A platform as claimed in claim 9, wherein the retaining means comprise a plurality of wires extending between first and second substantially parallel sides of the frame.

11. A platform as claimed in any preceding claim, wherein there is provided a walkway moveable over the retaining means.

12. A platform as claimed in any preceding claim, wherein the platform is also provided with permanent buoyancy means.

13. A platform as claimed in any preceding claim, wherein there is provided means to improve the food supply available to the stock by providing an environment conducive to the production of algae/phytoplankton.

14. A platform as claimed in claim 13, wherein such an environment is provided by an incubator provided within the at least one chamber of adjustable buoyancy.

15. A platform as claimed in claim 14, wherein said chamber has an aperture, and said incubator provides an ultraviolet light source.

16. A platform as claimed in claim 14 or 15, wherein said incubator provides means for heating the water contained within the chamber and insulating means.

17. A platform as claimed in claim 15, wherein said aperture is formed in the base of said chamber.

18. A platform as claimed in claim 16, wherein energy for the light source and heating means is provided by wind or wave power generation or any other suitable means.

19. A platform as claimed in any preceding claim wherein there are provided means to improve the flow of nutrient/plankton rich water to shellfish stock suspended from said platform.

20. A method of fish-farming comprising submerging a platform to a chosen depth and retaining same substantially thereat, the platform comprising a frame having one or more chambers of adjustable buoyancy retained in association therewith, the frame further having means for retaining fish stocking means therebelow, the platform being retained at the chosen depth by means or the one or more chambers.

21. A fish-farming platform comprising a frame having one or more buoyant chambers retained in association therewith, the frame further having means for retaining fish stocking means therebelow, the retaining means comprising one or more wires extending at least partially across the frame such that fish stocking means, such as ropes or lantern nets, may be hung therefrom.

22. A fish-farming platform having fish stocking means and including circulation apparatus adapted to provide flow of nutrients/plankton rich water to the fish stocking means.

23. A fish-farming platform as claimed in claim 22, wherein the fish stocks are shellfish.

24. A fish-farming platform as claimed in claim 22 or claim 23, wherein the platform is wholly or at least partially submersible.

25. A fish-farming platform as claimed in any claims 22 to 24, wherein water is redirected from or near the surface of the body of water in which the platform is located to a position at or below the lowermost shellfish stocks suspended from the platform.

26. A fish-farming platform as claimed in claim 25, wherein the apparatus causes the platform to rotate, in use.

27. A fish-farming platform as claimed in any claims 22 to 26, wherein said apparatus utilises wave, wind or tidal power, or any combination of the three.

28. A fish-farming platform as claimed in claim 27, wherein the apparatus provides a plurality of sails intended to impart rotational motion to the platform when acted upon by tidal current flow.

29. A fish-farming platform as claimed in claim 28, wherein the sails further serve to direct water captured by the sails towards the shellfish stocks.

30. A fish-farming platform as claimed in claim 25, wherein the apparatus provides at least one pump located within the platform, said pump having at least one inlet and an outlet, and means to drive said pump.

31. A fish-farming platform as claimed in claim 30, wherein the pump is being driven by energy derived from either a wind turbine or by wave motion.

32. A fish-farming platform as claimed in claim 31, wherein the pump takes the form of a shaft driven low head/high volume type pump.

33. A fish-farming platform as claimed in claim 31, wherein the pump takes the form of a buoyant spool which is free to oscillate under wave motion.

34. Circulation apparatus adapted to provide flow of nutrient/plankton rich water to fish stocking means of fishfarming platform.

35. A fish-farming platform as hereinbefore described with reference to Figs 1 to 2 of the accompanying drawings.

36. A fish-farming platform as hereinbefore described with reference to Figs 3 to 6 of the accompanying drawings.

37. A fish-farming platform as hereinbefore described with reference to Figs 7 to 16 of the accompanying drawings.

38. A fish-farming platform as hereinbefore described with reference to Figs 17 to 19 of the accompanying drawings.

39. A fish-farming platform as hereinbefore described with reference to Figs 20 to 21 of the accompanying drawings.

40. A fish-farming platform as hereinbefore described with reference to Figs 22a to 22c of the accompanying drawings.