AU3522601A - Shellfish aquaculture method and apparatus - Google Patents

Description

Regulation 3.2

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

(ORIGINAL)

Name of Applicant: Actual Inventor: Address for Service: Invention Title: Searl Seafoods Pty Limited Charles Mark Searl DAVIES COLLISON CAVE, Patent Attorneys, 1 Little Collins Street, Melbourne, Victoria 3000.

Shellfish aquaculture method and apparatus Details of Associated Provisional Application No: PQ6943 17 April 2000 The following statement is a full description of this invention, including the best method of performing it known to me/us: -1- P:'OPER\MKRSPEClIrack-capdoc- 1714,00 -2- SHELLFISH AQUACULTURE METHOD AND APPARATUS FIELD OF THE INVENTION The present invention relates to an artificial shellfish aquaculture environment and to related methods of culturing shellfish.

BACKGROUND OF THE INVENTION 10 It is an increasingly recognised problem that the fishing industry has for many years been engaging in non-sustainable levels of fishing with the result that world fish stocks are rapidly being depleted. For this reason government, environmental and fisheries agencies in many countries have introduced fisheries boundaries and strict quotas of the types of catch which may be harvested from them. This system of quotas applies equally to 15 shellfish which may be removed from natural reefs, for example, by divers.

In Australia State Departments of Fisheries and Wildlife have introduced marine parks which set aside coastal marine regions as conservation areas where no fishing is allowed.

The introduction of these marine parks has meant that the area available for exploitation by the fishing industry has been reduced. This has particularly affected the shellfish section i of the industry which had previously relied upon harvesting shellfish such as abalone, muscles, clams and oysters from reef areas which now fall within the boundaries of marine parks. The result of these restrictions, which are necessary from an environmental and industry sustainability perspective, is that it will be increasingly difficult to meet the demands for shellfish, and in particular for abalone, which is considered to be a delicacy particularly in a number of Asian countries. It is apparent therefore that other more sustainable methods of meeting the international demand for shellfish will be required.

Methods of culturing oysters in a tidal marine environment are well known. These methods, in their simplest form, simply involve providing racks on the sea floor, which will generally be immersed in water at high tide and dry at low tide, to which the oysters P.OPERi KR\SPECI'rack-~cp do-I7/4100 -3attach and grow until they reach an appropriate size for harvesting. This relatively simple process is effective because oysters will happily grow on a wide variety of substrates and do not require special care or attention. This is not the case with other species of shellfish, and particularly abalone, which have not previously been successfully cultured in a marine environment.

Numerous aquaculture methods for culturing shellfish have been, and continue to be conducted on land. These methods generally involve breeding of the organism in tanks of sea water which is filtered and maintained at an appropriate temperature. Immature 10 organisms are then transferred to growing tanks where they are maintained until ready for harvest. Although such methods may be successful in producing a good quality shellfish S•product they involve high capital and ongoing costs. There are also significant risks associated with disease which can readily affect the whole shellfish stock in this type of contained environment.

•It has been proposed in the past to breed young shellfish in a controlled environment on land and to then reintroduce the shellfish once they reach an appropriate size to a controlled marine environment where they can be monitored and where predators can be .o excluded. Again, however, such methods involve significant capital and operational costs and can be affected by disease transmission in the immature organisms.

ooooe The present invention seeks to overcome problems associated with prior art shellfish aquaculture methods and in particular, to provide a lower capital and operational cost system which can be used in a marine environment. Other objects of the present invention will become apparent from the following detailed description thereof.

SUMMARY OF THE INVENTION According to one embodiment of the present invention there is provided an artificial shellfish aquaculture environment comprising a platform installed above a sea floor and P:\OPER\NIKR\SPECr.ck-ckp doc.- 171400 -4under water level, the platform supported at a height above the sea floor sufficient to ensure clearance above variable sea floor level; the platform adapted to retain a plurality of shellfish support blocks to which is attached flora appropriate for cultivation of particular shellfish species.

Preferably the shellfish support blocks are bricks or building blocks having one or more bores or channels therein.

In one embodiment a non-corrodible material is located between the shellfish support 10 blocks and the platform. In a further embodiment the platform is produced from metal and is in electrical communication with a sacrificial anode.

:In another embodiment of the invention the platform has a modular construction.

Preferably the shellfish are oysters, muscles or clams. Particularly preferably the shellfish .are abalone.

When the shellfish are abalone the flora includes buoyant weed attached by its roots to the oooo shellfish support blocks. Preferably the buoyant weed is cray weed and/or bubble weed.

Also when the shellfish is abalone the flora include algae. Preferably the algae is red algae and/or pink coralline algae. Preferably the algae is attached on abalone shells transferred from a natural abalone growth environment, and which are attached to the shellfish support blocks.

In another embodiment of the present invention there is provided a method of culturing abalone comprising the steps of: introducing abalone on to shellfish support blocks of an artificial shellfish aquaculture environment which comprises a platform adapted to retain the blocks, installed above a sea floor and under water level, the platform supported at a height above the sea floor sufficient to ensure clearance above variable sea floor level; P:'OPERWMKR SPEClVck-ap doc-174/00 buoyant weed being attached to the blocks by its roots and abalone shells transferred from a natural abalone growth environment which have algae thereon also being attached to the blocks; (ii) regularly inspecting artificial shellfish aquaculture environment and removing abalone predators if present; (iii) harvesting cultured abalone when they reach an acceptable size.

Preferably the buoyant weed is cray weed and/or bubble weed and preferably the algae is red algae and/or pink coralline algae.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be described by way of example only with reference to the drawings, wherein: Fig. 1 shows an upper perspective view of a platform according to the invention on its supporting legs, with shellfish support blocks in position thereon; and Fig. 2 shows a side view of an artificial shellfish aquaculture environment 20 according to the invention which is located on the sea floor.

o* ooooo DETAILED DESCRIPTION OF THE INVENTION Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

The present invention provides a habitat suitable for culturing shellfish which can be installed in a marine environment. The artificial shellfish aquaculture environment according to the invention can be used for culture of a variety of shellfish such as oysters, P.OPER\V KR\SPECr ack-cap d- 17/4/00 -6muscles, clams and abalone. It has, however, been found particularly useful for the culture of abalone which to date have been difficult to culture successfully on a commercial scale at a reasonable cost. By installing the artificial aquaculture environment on the sea floor there is as a result no need to provide buildings, tanks, water filtration and temperature monitoring equipment, lighting or the like.

The invention comprises a platform which can be installed above the sea floor but under water level, although installation in a tidal zone may be appropriate for particular shellfish types. The platform is configured in such a manner that it can retain a number of shellfish 10 support blocks which provide the environment for shellfish habitat. In one aspect of the invention, the platform constitutes a modular metallic frame where individual modules can be pieced together to form a large platform area. The platform may include inverted Tsection crossbearers sized to fit rows of shellfish support blocks therebetween and to provide a slight separation between each of the rows. It is, however, possible for the S 15 platform to be constructed from timber or concrete, or indeed for it to retain the shellfish support blocks or other shellfish growth habitat matrix by a different means.

The platform will be supported by legs so that it is positioned above the sea floor.

Preferably the legs will penetrate some considerable depth, for example at least one and preferably at least two to three metres beneath the sea floor in order to at the same time provide stability for the platform and to ensure clearance of the platform above the variable sea floor level. The sea floor level may vary as a result of the tides, currents and water turbulence by the deposition or removal of sand. Preferably therefore the platform will be retained at least about a meter above the sea floor. In a preferred embodiment of the invention the platform support legs will penetrate approximately two thirds of their length beneath the sea floor and will have approximately one third of their length above the sea floor.

The platform and its supporting legs may conveniently be constructed from metal such as for example aluminium, stainless steel, galvanised iron or the like. In order to prevent corrosion of the platform and its supporting legs it may conveniently be placed in electrical P:\OPERMKR\SPECI-ack-cp do- 17/4/00 -7communication with a sacrificial anode, as would be well understood by persons skilled in the art. Because the present inventors have identified that contact of concrete blocks with an aluminium platform may result in chemical degradation of both components, if the platform is to be produced from aluminium it is preferable that a layer of non-corrosive material should separate these two components. Layers or sheets of polymer or plastics material may be utilised in this manner. In particular, the use of polyurethane has been found to be advantageous. In one embodiment polyurethane based material known as SikaflexTM, which is applied in a flowable form, has been used effectively.

10 The shellfish support blocks may for example constitute bricks, building blocks or rocks which preferably have pitted surfaces which immature shellfish may utilise as a habitat protected from water currents and predators. It is also preferred that the shellfish support S °blocks have larger bores or cavities which will serve to increase the surface area to which shellfish can attach. Particularly suited therefore as the shellfish support blocks are building blocks or bricks produced with internal cavities. While the shellfish support blocks may be maintained within the platform simply by virtue of their weight, it is of course possible for fastening means to be provided within the platform to ensure the blocks are not dislodged in rough seas. For example a retaining clip attached to the border of each g platform module may extend past an edge of each row of blocks. Alternatively, the bores 20 or cavities within the blocks can be used to pass securing straps or other fastening means through each row of blocks retained on the platform and to then in turn fasten these blocks to the platform structure.

It is preferred that the artificial shellfish aquaculture environment will be established on a region of the sea floor which has a sandy, shale or muddy base but which does not support significant amounts of vegetation. Establishing the aquaculture environment in such an area will help to prevent the influx of predators. The prevention of infestations of predators within the artificial shellfish aquaculture environment is also aided by retaining the platform above the sea floor so that water flow beneath the platform is maintained.

P:OPER\IKRSPECIack-p doc- I 7/400 -8- An example of the platform according to the invention is shown in Fig. 1 wherein the platform is comprised of four modular sections 2 each containing rows of hollow shellfish support blocks 3. The platform is supported by a number of support legs 4 intended to be embedded within the sea floor. Naturally, the number and location of the support legs will need to be appropriate for retaining the weight of the platform and its contents. In the example of the invention shown in Fig. 1 the support legs 4 have feet 5 along their length which serve to minimise movement of the legs within the sea floor. Braces 6 between adjacent legs and the platform are also provided in order to ensure stability of the structure.

10 Fig. 2 shows a side view of one embodiment of an artificial shellfish aquaculture .environment according to the invention. In this embodiment the platform 1 which constitutes two modules 2 joined together is supported above the sea floor 7 by the support legs 4. The support legs include feet 5 within the sections embedded within the sea floor 7 to aid stabilisation and braces 6 are present between adjacent support legs 4 and the 15 platform 1. Shellfish support blocks 3 are retained within the platform 1 to which are 0 °"attached buoyant weeds 8 to provide a protected habitat for shellfish cultivation.

oooo The present inventor has determined that the most satisfactory environment for shellfish 0 ro can be established by ensuring the presence of flora including buoyant weed or kelps, on the shellfish support blocks. The buoyant weed serves to provide a protected environment for the shellfish and also provides a site for location and fertilisation of shellfish sporn which can then migrate down along the weed to the protected habitat provided by the shellfish support blocks. The buoyant weeds will be attached by their roots to the shellfish support blocks, for example by the use of a non-toxic adhesive or by strapping around the blocks with wire, rope or preferably plastics or rubber material such as elastic bands or bicycle inner tubes. Attachment in this way will allow weed which has been transplanted from its natural location an opportunity to grow into and around the shellfish support blocks to be permanently retained thereon. For example, and especially in the case where the shellfish is abalone, the buoyant weed may constitute cray weed and/or bubble weed.

PAOPER,\MKR\SPECIkr.ck-cap doc- 17/4/00 -9- The present inventors have also determined that the most successful shellfish growth is achieved when sources of algae (also considered to constitute "flora") are present within the shellfish aquaculture environment. One successful means by which algae can be introduced into the aquaculture environment is by the transplant of shells from their natural habitat, which have algal growth on their outer surface. For example, in the case of abalone, organisms which have been removed from a natural reef and have had their meat removed may then have the shell attached, for example by the use of adhesive or similar means to the attachment of the weeds as referred to above, to the shellfish support blocks.

In this way algal populations can readily be established which will be in close proximity to 10 the shellfish so that the shellfish may utilise them as a food source. In the case of abalone it may be beneficial to establish the growth of pink coralline algae and/or red algae in order to support abalone cultivation.

.o.

S In cultivating the shellfish it is necessary to initially establish a parent colony of organisms.

This may for example be conducted by transplanting a number of male and female shellfish from a natural habitat. Sporn from these shellfish will be released into the water about the aquaculture environment, some of which may be retained upon the buoyant i" weeds, which provide an ideal location for fertilisation. Fertilised shellfish can then migrate (as they are generally light sensitive and will seek to migrate away from light) down the weeds and into protected pits or cavities of the shellfish support blocks. It is here that they will be able to grow and mature into larger organisms, particularly with the assistance of the food source provided by the presence of algae.

In establishing a colony of organisms it is also possible to transplant juvenile organisms, preferably from a hatchery environment. In the case of abalone, juvenile organisms may for example be from 5 mm to 50 mm, more likely approximately 20 mm, in diameter.

It is a preferred aspect of the invention for divers to conduct regular inspections of the aquaculture environment, particularly in order to identify or eliminate potential predators to the shellfish that may be present. In the case of abalone potential predators include octopus, crayfish, crabs, sea urchins and fish such as Port Jackson sharks and bearded P:'OPER\MKR\SPECIIck-cap.do- 17/4/00 morwong. This regular inspection by divers will serve to increase the survival rate, particularly of immature organisms.

The artificial shellfish aquaculture environment according to the invention can readily be installed by dropping the constituent components from a boat or floating platform to the sea floor in the region where the aquaculture environment is intended to be established.

The support legs of the platform can then be buried into the sea floor in the appropriate position and modular components of the platform can be attached thereto. The shellfish support blocks can then be positioned within the platform and retained as desired, after 10 which the appropriate marine flora, such as buoyant weed or algae, and parent shellfish organisms, can be put in place, as outlined above.

When the shellfish species reach the acceptable size they can be harvested by divers.

It is to be recognised that the present invention has been described by way of example only and that modifications and/or alterations thereto, which would be apparent to a person skilled in the art based upon the disclosure herein are also considered to fall within the scope and spirit of the invention, as defined in the appended claims.

0* 00 0.

Claims (14)

1. An artificial shellfish aquaculture environment comprising a platform installed above a sea floor and under water level, the platform supported at a height above the sea floor sufficient to ensure clearance above variable sea floor level; the platform adapted to retain a plurality of shellfish support blocks to which is attached flora appropriate for cultivation of particular shellfish species.

2. The artificial shellfish aquaculture environment according to claim 1 wherein the 10 shellfish support blocks are bricks or building blocks having one or more bores or channels therein.

3. The artificial shellfish aquaculture environment according to either claim 1 or claim S2 wherein non-corrodible material is located between the shellfish support blocks and the platform.

4. The artificial shellfish aquaculture environment according to either claim 1 or claim 2 wherein the platform is produced from metal and is in electrical communication with a sacrificial anode.

5. The artificial shellfish aquaculture environment according to any one of claims 1 to 4 wherein the platform has a modular construction.

6. The artificial shellfish aquaculture environment according to any one of claims 1 to 5 wherein the shellfish are oysters, mussels or clams.

7. The artificial shellfish aquaculture environment according to any one of claims 1 to 6 wherein the shellfish are abalone.

8. The artificial shellfish aquaculture environment according to claim 7 wherein the flora includes buoyant weed attached by its roots to the shellfish support blocks. P:'OPERM KRSPECIIrack-capdoc- 17/400 -12-

9. The artificial shellfish aquaculture environment according to claim 8 wherein the buoyant weed is cray weed and/or bubble weed.

10. The artificial shellfish aquaculture environment according to any one of claims 7 to 9 wherein the flora includes algae.

11. The artificial shellfish aquaculture environment according to claim 10 wherein the algae is red algae and/or pink coralline algae.

12. The artificial shellfish aquaculture environment according to either claim 10 or claim 11 wherein the algae is on abalone shells transferred from a natural abalone growth environment, which are attached to the shellfish support blocks. 15

13. A method of culturing abalone comprising the steps of: S introducing abalone on to shellfish support blocks of an artificial shellfish aquaculture environment which comprises a platform adapted to retain the blocks, installed above a sea floor and under water level, the platform supported at a height above the sea floor sufficient to ensure clearance above variable sea floor level; buoyant weed being attached to the blocks by its roots and abalone shells :transferred from a natural abalone growth environment which have algae thereon also being attached to the blocks; (ii) regularly inspecting artificial shellfish aquaculture environment and removing abalone predators, if present; (iii) harvesting cultured abalone when they reach an acceptable size.

14. The method according to claim 13 wherein the buoyant weed is cray weed and/or bubble weed. P:\OPER\N1KR'SPECtI k-p.do- 1 7/100O -13- The method according to either claim 12 or claim 13 wherein the algae is red algae and/or pink coralline algae. DATED this 17th day of April 2001 Searl Seafoods Pty Limited By DAVIES COLLISON CAVE Patent Attorneys for the Applicant