AU2007200790A1 - Shellfish farming device - Google Patents

Description

a) C4 Regulation 3.2

AUSTRALIA

Patents Act 1990 (Cth) KATIE RAE McCANN COMPLETE SPECIFICATION FOR A STANDARD PATENT (ORIGINAL) Invention Title: SHELLFISH FARMING DEVICE The following statement is a full description of this invention, including the best method of performing it known to me: 201943012_1 SHELLFISH FARMING DEVICE SFIELD OF THE INVENTION c The present invention relates broadly to a device for farming shellfish, and relates particularly although not exclusively to a device for holding immature oysters, or spats during their maturation at an oyster farm.

BACKGROUND OF THE INVENTION Traditional oyster farming in coastal and estuarine waters uses stick and tray culture.

Initially, sticks that have been dipped in tar and then coated in concrete are attached to cross beams placed in water. These sticks are then populated by natural spat fall. The concrete surface is good for the spat to adhere to, while the tar protects the stick from borers and rot. The spats are allowed to mature on the sticks for approximately 18 months.

The oysters are then shaken off the sticks and put loosely in trays for approximately 9 more months to fatten or grow out.

The stick system is very costly and time consuming, not only to construct but also to maintain. Because the tar coating leaches and pollutes the water the stick system also impacts the natural marine environment it is used in. Also, the densely packed sticks shade the ground beneath them killing up to 90% of sea grass. The tar is also carcinogenic and so its use is undesirable in the production of food.

Some of the disadvantages of stick and tray culture have been overcome using single seed culture. In this technique immature spats derived from natural spat fall or from a hatchery are put into trays. Single cell culture produces highly desirable cup shaped oysters.

However, the oysters that are grown using this technique are usually of different sizes and the yield is very low. This is because strong winds, a storm or a tide can agitate the trays causing the spats to crowd at one end. This restricts them from feeding and growing properly. This problem can be overcome by continually attending to the trays to ensure the spats are evenly distributed within them. However, this is labour intensive and thus expensive.

It is clear that current oyster farming methods suffer from at least the following problems: 201943150vl S1. The ground below the sticks or trays is shaded, killing sea grass and preventing Sregrowth; 2. tar coating the sticks can pollute the water and contaminate the food oysters; S3. the farming methods are highly labour intensive; 4. when the spats crowd they grow to different sizes; and the yield of mature spats is low.

SUMMARY OF THE INVENTION According to one aspect of the invention there is provided a shellfish farming device comprising: a container being adapted to hold shellfish; and floatation means associated with the container, the flotation means being arranged to float the container at or near a water surface.

Preferably the container is perforated. More preferably the size of the perforations are smaller than the predominant size of the shellfish. Even more preferably the size of the perforations is also smaller than a significant predator in a local shellfish farming area.

Preferably the flotation means is attached to the outside of the container by attaching means. More preferably the attaching means include a line or fasteners for securing the flotation means to the container.

Preferably the container is formed of an elongated mesh sleeve having closed opposing ends. More preferably the device also comprises closure means for attachment to the mesh sleeve for its closure. Even more preferably the closure means include cable ties.

Preferably the device further comprises tensioning means operatively coupled to the container for its retention into a substantially rigid form of the mesh sleeve. More preferably the tensioning means extends longitudinally along the mesh sleeve and wraps around its ends for closure of the sleeve.

Preferably the tensioning means includes an elongate member secured along its length to the mesh sleeve and anchored at its opposing ends to said sleeve. More preferably the member is in the form of a wire interwoven through the mesh and anchored to the mesh by a hook formed at each end of the wire.

Preferably the container intermediate its ends is shaped generally ellipsoidal in transverse cross section.

Preferably the flotation means is elongated and positioned lengthwise against a flatter side of the container.

According to another aspect of the invention there is provided a shellfish farming apparatus comprising: a container being adapted to hold shellfish; floatation means associated with the container, the floatation means being arranged to float the container at or near a water surface; and anchoring means, being arranged to connect the container to a fixed point of ground.

Preferably the anchoring means includes one or more couplings connected to the container.

More preferably the anchoring means also includes a tethering line connected at one end to each of the couplings. Still preferably the anchoring means further includes a post secured to the ground to which one end of the tethering line is connected. Still more preferably the post is a PVC tube. Yet still more preferably the post is secured by thrusting one of its ends into the ground.

Preferably the flotation means is at least in part made of closed cell foam.

Preferably the mesh sleeve is at least in part made of polymer.

BRIEF DESCRIPTION OF THE FIGURES In order to achieve a better understanding of the nature of the invention a preferred embodiment of a shellfish farming device will now be described, by way of example only, with reference to the accompanying figures.

Figure 1 is a perspective view of the device from above and off to one side of the device.

Figure 2 is an elevational view of one end of the device.

Figure 3 is an elevational view of the other end of the device Figure 4 is another perspective view of the device from below and off to one side of the device.

Figure 5 depicts the removal of spats from one end of the open device.

Figure 6 is a side elevational view of the device floating in water and tethered to posts.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Figure 1 shows one embodiment of a shellfish farming device 10 according to the invention. The device 10 comprises a container 12 being adapted to hold immature shellfish, such as oyster spats, during one stage of their production. There are floatation means 14 associated with the container 12. The floatation means is shown with a cutaway to aid in the visualisation of the device. The flotation means 14 are arranged to float the container 12 at or near a water surface. The floatation means 14 are attached to the container 12 by attaching means, such as line 16, although other attaching means such as fasteners may be used.

In this embodiment the container is formed as an elongated mesh sleeve 12 closed at its opposing respective ends 18 and 20. The perforations such as 22 of the mesh 12 allow water to freely flow across the spats, carrying nutrients to the spats and removing waste excreted by them. Water flow across the spats is aided by the action of waves or wind which cause the device 10 to rock and thus move the container through the water. The size of the perforations 22 are smaller than the predominant size of the spats when they are first put into the container 12 enabling their retention. The perforations, such as 22, are also smaller than any significant spat predator in a local shellfish farming area, and thus the mesh 12 forms a protective barrier between the spats and their predators.

The mesh sleeve 12 is at least in part made of a pliable inert polymer and can thus be easily forced into shape. As shown in figure 2 at least one end 18 of the mesh sleeve 12 is closed by closure means such as cable ties 24. In this embodiment the device 10 also comprises tensioning means 26 in the form of an elongated member such as a resiliently bendable plastic wire. The wire 26 extends along the mesh sleeve 12 and wraps around the ends 18 and 20 for securement of the sleeve 12. Figure 3 shows the other end 20 being closed by the tensioning means 26. The tensioned wire 26 also acts to close an opposite end 20 of the mesh sleeve 12. As shown in figure 4 the wire 26 is generally held in tension by hooks 28 and 30 formed at each end of the wire 26 that are anchored to the mesh 12. As can be seen through the cutaway of the floatation means in figure 1 the wire 26 is interwoven through the mesh 12 to secure it along its length to the mesh container 12. The tensioning means 26 also retains the mesh sleeve 12 in a substantially rigid form such that intermediate its ends 18 and 20 it has a generally ellipsoidal transverse cross section.

The floatation means 14 is at least in part made of closed cell foam. The best known foam to use is or is similar to "floatation 28" manufactured by Thermoplastic Foam Industries of NSW, Australia. The properties of this foam which makes it desirable to use include its low water (or other fluid) absorption even when punctured, durability, cost effectiveness, environmental friendliness, lack of toxicity and the absence of any maintenance needs.

The foam 14 is elongated and is positioned lengthwise against a flat side of the container- 12. This helps stabilise the device 12 in strong winds, storms or tides. This stabilisation is particularly desirable because it prevents the unwanted movement of the spats to one end of the container 12. When the spats are not uniformally distributed throughout the container 12 more spats die than otherwise. The surviving spats tend to be of a lower quality, a smaller average size and have large size variations. Size variations in oysters is undesirable because it slows down shucking during their processing stage. To prevent these problems without stabilisation, each container would require regular attention to redistribute the spats evenly, which is a labour intensive and an expensive process. Thus, a stabilised device 12 results in less spat death, higher quality and larger spats, and less variation in spat size for less costs.

As shown in figure 5 the container 12 is openable to allow the insertion or the removal of spats. This is achieved by pulling the hook 28, near to the container end 20 without cable ties 24, until it deforms sufficiently to disengage from the mesh. The end of the sleeve 12 is then opened to allow access to the spats. Reclosure of the container is achieved by reengaging the hook 28 to the mesh 12.

As shown in figure 6, the device 10 is anchored to the ground 31 beneath the water 33.

There are couplings 32 and 34 connected to the container. In this embodiment the couplings are shark clips 32 and 34, best observed in figure 1, with an eye, such as 36, at one end through which the wire tensioning means 26 pass through. One end of a tethering line, such as 38, is tied to the shark clip, such as 32 and 34, and the other end is tied to a PVC tube such as 40 that has been thrust into the ground 31 beneath the water 33. This prevents the device from being washed away by tide or storm, or blown away.

It will be appreciated that the mesh container 12 does not block sunlight from reaching the ground 33 beneath it, but only filters the sunlight. Thus the container 12 does not prevent the growth of aquatic grasses. This minimises the environmental impact of using the device 12, and so allows its use in more environmentally sensitive areas.

It will be appreciated by the person skilled in the art that the invention at least in its preferred form has at least the following advantages: 1. Sunlight is not blocked by the device, and so sea grass can grow beneath the device; 2. Due to the device's inert composition, there is no pollution of the water or contamination of the oysters by, for example, tar; 3. There is reduced need to attend to crowded spats; 4. The spats grow to a uniform and relatively larger size because the stabilisation reduces crowding; and The shellfish yield is higher.

It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. For example, the floatation means may be provided by an air pocket in an inverted or closed vessel (or container itself), or the container may be composed of rigid metal or plastic with bored apertures for perforations. It will also be appreciated that the device could be used for the production of shellfish other then oysters, such as abalone. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Claims (25)

1. A shellfish farming device comprising: a container being adapted to hold shellfish; and floatation means associated with the container, the flotation means being arranged to float the container at or near a water surface.

2. A shellfish farming device defined by claim 1 wherein the container is perforated.

3. A shellfish farming device defined by claim 2 wherein the size of the container perforations are smaller than the predominant size of the shellfish.

4. A shellfish farming device defined by either of claims 2 or 3 wherein the size of the container perforations are smaller than a significant predator in a local shellfish farming area.

A shellfish farming device defined by any one of claims 1-4 wherein the flotation means is attached to the outside of the container by attaching means.

6. A shellfish farming device defined by claims 5 wherein the attaching means include a line or fasteners for securing the flotation means to the container.

7. A shellfish farming device defined by any one of claims 1-6 wherein the container is formed of an elongated mesh sleeve having closed opposing ends.

8. A shellfish farming device defined by claim 7 further comprising closure means for attachment to the mesh sleeve for its closure.

9. A shellfish farming device defined by claim 8 wherein the closure means include cable ties.

A shellfish farming device defined by any one of claims 7-9 further comprising tensioning means operatively coupled to the mesh sleeve for its retention into a substantially rigid form of the mesh sleeve.

11. A shellfish farming device defined by claim 10 wherein the tensioning means extends longitudinally along the mesh sleeve and wraps around its ends for closure of the sleeve.

S12. A shellfish farming device defined by claim 11 wherein the tensioning means Sincludes an elongate member secured along its length to the mesh sleeve and anchored at its opposing ends to said sleeve.

13. A shellfish farming device defined by claim 12 wherein the elongate member is in the form of a wire interwoven through the mesh and anchored to the mesh by a hook formed at each end of the wire.

14. A shellfish farming device defined by any one of claims 1-13 wherein the container Sintermediate its ends is shaped generally ellipsoidal in transverse cross section.

A shellfish farming device defined by any one of claims 1-14 wherein the flotation means is elongated and positioned lengthwise against a flatter side of the container.

16. A shellfish farming apparatus comprising: a container being adapted to hold shellfish; floatation means associated with the container, the floatation means being arranged to float the container at or near a water surface; and anchoring means, being arranged to connect the container to a fixed point of ground.

17. A shellfish farming apparatus defined by claim 16 wherein the anchoring means includes one or more couplings connected to the container.

18. A shellfish farming apparatus defined by claim 17 wherein the anchoring means also includes a tethering line connected at one end to each of the couplings.

19. A shellfish farming apparatus defined by claim 18 wherein the anchoring means further includes a post secured to the ground to which one end of the tethering line is connected.

A shellfish farming apparatus defined by claim 19 wherein the post is a PVC tube.

21. A shellfish farming apparatus defined by either claim 19 or 20 wherein the post is secured by thrusting one of its ends into the ground.

22. A shellfish farming device defined by any one of claims 16-21 wherein the container is formed of an elongated mesh sleeve having closed opposing ends.

23. A shellfish farming apparatus or device defined by any one of claims 1-22 wherein the flotation means is at least in part made of closed cell foam.

24. A shellfish farming apparatus or device defined by any one of claims 1-23 wherein the container is at least in part made of polymer.

25. A shellfish farming device substantially as herein described with reference to and as illustrated in the accompanying figures.