WO2009009838A1

WO2009009838A1 - Improvements in or relating to mollusc farming

Info

Publication number: WO2009009838A1
Application number: PCT/AU2008/001044
Authority: WO
Inventors: Peter Kvietelaitis
Original assignee: Peter Kvietelaitis
Priority date: 2007-07-19
Filing date: 2008-07-18
Publication date: 2009-01-22

Abstract

The present invention provides an organic or plastics material aquaculture substrate or medium for use with or as a mollusc collection and/or growing aid, sock or oversock, the aquaculture substrate or medium including a source of iron that is provided within or on the surface of the substrate or medium.

Description

IMPROVEMENTS IN OR RELATING TO MOLLUSC FARMING

TECHNICAL FIELD

The present invention relates to improved apparatus and/or methods for use in the aquaculture farming industry, and relates particularly, though not exclusively, to apparatus and/or methods for collecting and/or growing molluscs. It will be convenient to hereinafter describe the invention in relation to the farming of mussels, however it should be appreciated that the present invention is not limited to that use only.

BACKGROUND ART

Any discussion of documents, devices, acts or knowledge in this specification is included to explain the context of the invention. It should not be taken as an admission that any of the material forms a part of the prior art base or the common general knowledge in the relevant art in Australia or elsewhere on or before the priority date of the disclosure herein.

With increased demand for high quality produce, the aquaculture farming industry has developed smarter and more reliable techniques for culturing and harvesting marine life. Mussels, like other marine life, were historically harvested from the wild. However, as stocks have diminished, new methods of farming mussels have evolved.

A common mussel farming method now in vogue utilises collection lines, such as ropes or the like, which are suspended below the surface of a suitable body of water in order to collect seed mussels or mussel spat, which attach themselves to the lines in order to grow. "Mussel spat" means young mussel in the post larval stage, which is usually larger than 0.5 mm. They are usually measured as being up to a certain length, e.g. in accordance with Tasmanian Regulations, "mussel spat" means a mussel the shell of which is less than 40 mm in length. Mussel spat collect on these lines and as they grow form dense clusters, in fact often to a density which is too large to allow growth and maturity. When the spat have reached sufficient size while growing on the collection line, a mussel farmer will withdraw the lines from the water to perform "mechanical" density adjustment, by separating, declumping, grading and injecting the immature mussel spat into a mesh sleeve, sock, net or the like, which forms part of a growing line.

"Sleeving" or "socking" is the operation by which mussel spat stripped from a collection line are loaded at a particular density per length into mesh sleeves or socks that make up part of a growing line. A sock is a long mesh tube commonly made of cotton and often strengthened with a strand of polypropylene twine which facilitates mussel attachment to a growing line at a more appropriate density to assist the growth of mussels when they are reintroduced into the water. Such socks can be decomposable, and hence, may only provide support for mussels for a short period of time. After a sock has perished, the mussels must rely on other parts of the growing line, or other mussels, for support.

A growing line may consist of a simple rope, or may be formed in a more complex manner, e.g. it may include a sock or other additional integers. For example, a growing line may incorporate a collection and/or growing medium such as the medium disclosed in International Patent Application No. PCT/AU2007/001890, filed on 7 December 2007 in the name of the present applicant, Peter Kvietelaitis, the entire contents of which is incorporated herein by this reference thereto. As mussels increase in size, those closest to the growing line rely on support from the growing line itself, by attaching themselves thereto, whilst those disposed radially outwardly thereof rely on attachment to other mussels for support. If a perishable sock is utilised, mussels in the vicinity thereof can initially also rely on this sock for support. After the sock disintegrates, mussels in the vicinity thereof can only rely on support from those mussels beneath them, or radially inward from them. It is at this point that the entire mussel crop is reliant on the foothold of those mussels (the supporting mussels) that have directly attached themselves to the growing line. The number of mussels that can safely attach themselves directly to a growing line is dependent on the diameter or surface area of the growing line itself. It thus becomes evident that, as mussels grow and hence weight increases, if supporting mussels lose their foothold, significant losses of crop can occur as large clusters of mussels fall away from the growing line and are lost. Furthermore, as heavily laden mussel growing lines are immersed in water, the water itself serves to create a buoyancy effect for the mussels that are attached to the growing lines. However, during harvest the mussel growing lines are lifted out of the water, meaning this buoyancy effect is lost. This loss of buoyancy means the weight of the mussels needs to be self-supporting, and can result in a significant increase in the losses associated with mussels falling away from the lines at the time of harvesting, in addition to any losses suffered during the growing period.

Losses associated with mussels peeling off or falling away from collection and/or growing lines will hereinafter generally be referred to as the "slide off effect".

Issues relating to the slide off effect and apparatus and methods for partially alleviating this problem are presented in International Patent Application Nos. PCT/AU2004/001238 and PCT/AU2005/000217, filed on 10 September 2004 and 18 February 2005 respectively, both in the name of the present applicant, Peter Kvietelaitis, the entire contents of which are incorporated herein by this reference thereto.

Traditionally, the slide off effect is dealt with by the attachment of support structures to a growing line (which is usually a rope), or by the process of oversocking at the appropriate time using diamond-shaped tubular mesh socks, which are non perishable. Oversocking may be applied to or incorporated onto a growing line to help provide more support to the maturing mussel crop, so that the supporting mussels are less likely to lose their foothold on the growing line and hence the risk of the slide off effect is reduced. The oversock completely encases the spat/maturing mussels and the growing line, which may include a sock (or partially decomposed sock). Alternatively, a collection line may be oversocked prior to any "mechanical" density adjustment, to reduce slide off effect.

In commercial mussel harvesting operations, a plurality of collection and/or growing lines may be suspended from a support structure (such as a buoy or another line). These lines are known as drop lines, or "droppers", and they may be attached at either end to buoys, or be otherwise supported. An alternative to a plurality of drop lines is a continuous line. Continuous lines may allow for easier handling as the collection or growing line can be removed from the marine environment, processed and returned to the marine environment in a continuous fashion. However, continuous spat collection or growing lines are onerous to attempt to oversock. As the available diamond-shaped oversock material is relatively stiff, same is generally unsuitable for oversocking continuous collection and/or growing lines/mediums.

A tubular oversock must be applied from a cartridge of oversock, in order to encase a growing line — the growing line is fed downwardly through the tubular cartridge, and oversock loaded on the outer sides of the cartridge is drawn up the outer sides of the cartridge and then drawn downwardly through the cartridge as the growing line passes therethrough. However, due to the properties of known (relatively stiff) oversocking material, only a limited amount can be placed on a cartridge. For a typical oversocking operation, only around 50 to 100 metres of this known oversock material can be loaded onto a cartridge. In comparison, for a socking operation using a cotton sock, around 1000 metres of material can be loaded onto a cartridge.

Known oversock material does not lend itself well to mechanisation of the process, particularly for a continuous growing line — changing or reloading cartridges is an onerous exercise for continuous lines. This oversock material is also onerous to apply to a single drop line and due to the relative stiffness of the material, does not load well onto cartridges and a far smaller length of material can be loaded onto a cartridge.

Another problem with the use of diamond-shaped tubular non-perishable netting is that its capacity to inhibit the slide off effect is negated once mussels have migrated to the outside of the mesh as the weight of those mussels tends to make the diamond shaped tubular netting rope-like. That is, it increases in length as it constricts.

In addition to all of the issues outlined above, of concern to mussel farmers is the problem faced when initially collecting commercially viable mussel spat. This problem often becomes apparent after a spat collection zone has produced good settlement initially but quantity, quality and reliability aspects diminish over time. It has also been observed that mussel byssal attachment becomes weaker over time (a period of years) in some "grown out" zones, particularly during critical periods of a growth cycle. This weakness of attachment leads to loss of mussels through the slide off effect, and hence, a reduced harvest.

Settlement becomes less reliable over time and commercially viable settlement does not occur in some instances, particularly where settlement is sporadic along the collection and/or growing medium. Spat may tend to settle in one region only (usually the upper region). It is not uncommon for the lower portion of a collection and/or growing medium to be unpopulated by mussel spat, allowing undesired organisms to colonise the vacant sections of the medium. These organisms can grow and add significant weight to the collection and/or growing medium and, in time, can even displace the settled spat.

A need therefore exists for improved mussel farming apparatus and methods that: may increase spat collection yield; may be used to decrease the tendency for collected spat and/or growing mussels to settle in uneven density distributions on a collection and/or growing line; and/or, may improve mussel byssal attachment to a collection and/or growing line leading to an increased harvest. It is also desirable to provide improved oversocking apparatus and methods to simplify the ease by which oversocking material may be applied to a collection and/or growing line.

Accordingly, it is an object of the present invention to provide an improved aquaculture apparatus and/or method which overcomes one or more of the difficulties of the prior art, or at least provides a useful alternative.

DISCLOSURE OF THE INVENTION

According to one aspect of the present invention there is provided an organic or plastics material aquaculture substrate or medium for use with or as a mollusc collection and/or growing aid, sock or oversock, the aquaculture substrate or medium including a source of iron that is provided within or on the surface of the substrate or medium.

In a practical preferred embodiment, said substrate or medium is a cotton sock that has been impregnated with iron, or an iron compound. In an alternative practical preferred embodiment, said substrate or medium is a cotton sock that includes strands of twine or yarn that has been impregnated with iron, or an iron compound. In either practical embodiment, it is further preferred that an additional source of iron is provided by way of the provision of a sacrificial linear strand containing iron, or an iron compound. In yet a further practical preferred embodiment, said substrate or medium is a plastics material collection and/or growing line or aid that has had an iron compound introduced therein during the plastics extrusion or molding process. Preferably said iron compound introduced therein during the plastics extrusion or molding process is an iron oxide colouring agent. In an alternative embodiment, said substrate or medium is a plastics material collection and/or growing line or aid that has been coated with a substance containing a source of iron. In this alternative embodiment, it is preferred that the substance containing a source of iron is an iron oxide or iron solution. In any of these plastics material preferred embodiments it is further preferred that an additional source of iron is provided by way of the provision of a sacrificial linear strand containing iron, or an iron compound.

In the case of the substrate or medium being constructed of an organic material, as for example cotton as previously defined, it is preferred that the substrate or medium is decomposable or perishable. According to yet a further aspect of the present invention there is provided an apparatus for applying an oversock produced from a planar aquaculture substrate to a collection and/or growing line, said apparatus including: a first guide means through which said collection and/or growing line and said planar aquaculture substrate are fed, said first guide means guiding said planar aquaculture substrate into a semi-tubular form around said collection and/or growing line; and, a second guide means located downstream of said first guide means through which said collection and/or growing line and said semi-tubular substrate are fed, said second guide means guiding said semi-tubular substrate into a tubular oversock, encasing said collection and/or growing line inside said oversock.

Preferably said first guide means is a circular orifice and said second guide means is a circular orifice having a smaller diameter than said first circular orifice. It is also preferred that said apparatus further includes a binding mechanism for applying a binding means to said oversock. Preferably said binding mechanism is a cartridge housing, and said binding means is a cotton sock. In an alternative embodiment, it is preferred that said binding means is a linear strand and said binding mechanism is a turret located downstream of said second guide means, said turret rotatable about the oversocked collection and/or growing line whereby said linear strand fed through said turret is wrapped about the oversocked collection and/or growing line.

Preferably said aquaculture substrate and/or said binding means includes a source of iron. In a practical preferred embodiment, said binding means is a cotton sock that has been impregnated with iron, or an iron compound. In an alternative practical preferred embodiment, said binding means is a linear strand that includes a source of iron, or an iron compound.

According to yet a further aspect of the present invention there is provided a method for applying an oversock to a collection and/or growing line, said method including the steps of: feeding a planar aquaculture substrate and said collection and/or growing line through a first guide means, said first guide means guiding said planar aquaculture substrate into a semi-tubular form around said collection and/or growing line; and, feeding said collection and/or growing line and the semi-tubular substrate through a second guide means, said second guide means guiding the semi-tubular substrate into a tubular oversock; whereby said collection and/or growing line is encased inside said oversock.

In accordance with a practical preferred embodiment, said method further includes the step of applying a binding means to said oversock. Preferably said aquaculture substrate and/or said binding means includes a source of iron. In one embodiment, said binding means may be a cotton sock which has been impregnated with iron, or an iron compound. In an alternative embodiment, said binding means may be a linear strand which includes a source of iron, or an iron compound.

According to yet a further aspect of the present invention there is provided a mussel cultivation method including the steps of: collecting spat mussels utilising a collection medium that is suspended in a body of water; declumping and/or grading the collected spat mussels; and, socking the collected spat mussels onto a growing medium utilising an organic material sock that contains a source of iron.

Preferably said organic material sock that contains a source of iron is a cotton sock that has been impregnated with iron or an iron compound. It is also preferred that said collection and/or growing medium also includes a source of iron.

The present invention may also provides for: molluscs produced through use of an aquaculture substrate, apparatus and/or method according to any one of the preceding paragraphs; and/or, use of an aquaculture substrate according to any one of the preceding paragraphs for collecting and/or growing mussels.

BRIEF DESCRIPTION OF THE DRAWINGS In order that the invention may be more clearly understood and put into practical effect there shall now be described in detail preferred constructions of improved mollusc farming apparatus and methods in accordance with the invention. The ensuing description is given by way of non-limitative example only and is with reference to the accompanying drawings, wherein: Figure 1 is a side view of a prior art mollusc culture growing arrangement, showing growing lines suspended beneath the surface of the water in order to provide support for molluscs as they grow;

Figure 2 is a side view of a further prior art mollusc culture growing arrangement, this time being a continuous collection or growing line arrangement showing the lines suspended beneath the surface of the water in loops in order to provide support for molluscs as they grow;

Figure 3 is a perspective view of a collection and/or growing line that has been oversocked in accordance with a preferred embodiment of the present invention; Figure 4 is a perspective view of an apparatus made in accordance with a preferred embodiment of the invention for applying an oversock to a collection and/or growing line;

Figure 5 is a perspective view of a roll of oversocking material used in accordance with a preferred embodiment of the present invention; and, Figures 6 to 10 are enlarged perspective views of various components or sections of the preferred oversocking apparatus shown in Figure 4, these views illustrating the preferred oversocking action that may be performed by utilising the preferred oversocking apparatus of the present invention.

MODES FOR CARRYING OUT THE INVENTION

In Figure 1 there is shown a prior art mollusc growing arrangement 10 suitable, for example, for growing mussels (not shown). Mollusc growing arrangement 10 includes a plurality of growing lines 12 adapted to be vertically suspended below the surface of the water 14 to provide a series of collection and/or growing media for mollusc cultivation. Growing lines 12 are suspended from a substantially horizontal support line 16. Support line 16 is suspended beneath the water surface 14 between a pair of buoys 18. Two substantially vertical support lines 20,22, each anchored to the seabed 24 at anchor points 26,28, are attached to respective buoys 18 in order to maintain the overall mollusc growing arrangement 10 at a chosen location.

The prior art growing lines 12 shown in Figure 1 each consist of a growing rope 30 carrying mussels (not shown) which have been socked with a mesh sock 32. Although shown in mollusc growing arrangement 10 as each including growing rope 30 and mesh sock 32, growing lines 12 may be embodied as a growing rope 30, or (less desirably) a mesh sock 32 used on their own. Alternative collection and/or growing mediums (not shown) such as those described in the present applicants aforementioned International Patent Application No. PCT/AU2007/001890 may also be substituted for a growing rope 30.

Mesh socks 32 are typically about 40 mm in diameter, and are usually knitted for ease of manufacture. Mesh socks 32 can be knitted into a variety of patterns, including square and diamond shapes.

Mesh tubes having a 40 mm diameter made of industry standard materials such as cotton, as are generally used for this purpose, do not have sufficient strength to support (for example) a two to four metre length of mature mussels growing thereupon. If so used, as mussel weight increases, the mesh sock 32 elongates, or stretches such that the "tube" is more akin to a rope. As socks 32 perish, or rot, crop loss becomes likely. For this reason, a central rope 30 is typically provided for the mussels to attach to, and such a rope 30 provides the strength of the growing line 12, or elongate support.

Shown attached to growing lines 12 and positioned at spaced-apart locations thereon are a plurality of aquaculture support devices 34 which reduce the incidence of slide off effect. In mollusc growing arrangement 10, aquaculture support devices 34 are embodied as support structures which are adapted to provide additional support for mussels to attach to as they grow. These support devices 34 may be those shown and described in the present applicants International Patent Application No. PCT/AU2004/001238.

In the harvesting operation, when aquaculture devices 34 have been attached to growing lines 12 and placed in the environment of mollusc growing arrangement 10, mussels are not only able to attach themselves to other mussels, growing ropes 30 and mesh sock 32, but can also attach themselves to support devices 34 for additional support. Support devices 34 provide platform-like supports for mussels that radiate from the vertically suspended growing lines 12. This platform-like attachment of mussels helps to reduce losses associated with the slide off effect.

In Figure 2 there is shown a further prior art mollusc growing arrangement 100 also suitable, for example, for growing mussels (not shown). Mollusc growing arrangement 100 includes continuous growing lines 120 adapted to be vertically suspended in loops below the surface of the water 140 for mollusc cultivation. Growing lines 120 are suspended from a substantially horizontal support line 160 (also known as long line) and can be looped over the support line 160 or otherwise attached. Support line 160 is suspended beneath the water surface 140 supported by a series of buoys 180. Two support lines 200, each anchored to the seabed 240 at anchor points 260, are attached to the support line 160 in order to maintain the overall mollusc growing arrangement 100 at a chosen location. As is clearly demonstrated by way of the prior art mollusc growing arrangements 10,100, shown in Figures 1 & 2, the advent of aquaculture generally means that intensive aquaculture farming within a relatively small area occurs, and this has the potential to deplete the required amounts of nutrients, particularly iron, in the environment. The demands of the industry on the water available mean that the nutrients freely available in the water are depleted, leading to a reduction in the production levels of high quality product.

The physical nature of aquaculture means that the water used, particularly for mussel production, is water in a natural environment, subject to natural events such as currents, tidal effects and increased or decreased run-off from the land, depending upon weather conditions. This can lead to a continual variation in the supply and availability of various nutrients to the organisms being farmed.

An aspect of the present invention stems from the inventor's realisation that bio-available iron in marine waters tends to be more concentrated at the surface with concentration decreasing in proportion to depth. Spat settlement occurs on the portions of spat collection or growing media or medium (e.g. lines 12,120) nearest to the water surface 14,140 and often no spat settlement occurs on lower portions of the media 12,120. Hence, a full column of spat is not collected, which impacts on the farmer's options for harvesting and may require the farmer to perform density adjustment and re-socking of the collected spat in order to obtain the correct density, and hence, a full column of spat on lines 12,120.

Trials and observations have indicated that the placement of iron into or onto spat collection mediums promotes spat settlement and colonisation and also more vigorous growth of the spat. It has also been observed that commercial spat settlement can fail with mediums that do not have sacrificial iron present, as a lower density of spat collects. Trials have shown that a full column of spat can be collected when an iron weight is added to a suspended spat collection medium, whilst mediums weighted with non-iron weights (such as concrete) did not produce a full column of spat.

In Figure 3 there is shown a collection and/or growing medium 320 which has been oversocked using an oversock 330 made in accordance with a preferred embodiment of the present invention. Oversock 330 is constructed of a flexible material that has been impregnated with iron, or contains a source of iron. When used to oversock a collection and/or growing medium 320, the introduction of iron into the aquaculture environment provided by way of oversock 330 means that farmers could reasonably expect to achieve a full column settlement of mussel spat. This, in turn, allows farmers to select an appropriate diameter of rope (if this is the chosen collection and/or growing medium 320), with the view to attracting the appropriate number of spat per metre on the collection and/or growing medium 320. Farmers could also use alternative collection media or mediums (not shown), such as that described in the present applicants aforementioned International Patent Application No. PCT/AU2007/001890, which may itself have been impregnated with iron, or provided with a source of iron, or when socking spat onto such a growing medium, could use a sock of perishable iron impregnated cotton netting (as will be described in further detail below). The growing medium could also be oversocked with an iron impregnated oversock, whether at the time of socking spat, or later.

As the iron source provided by way of an oversock 320, or any other suitable means made in accordance with the invention (herein after simply referred to as a "substrate"), starts to rust immediately upon being immersed in water, the iron oxide produced will attract marine organisms that assist in converting the iron into a bio-available form. This serves as a cue for mussel larvae that this is a suitable environment for settlement and encourages a strong byssal growth attachment. It is possible for the iron source to be present in the form of oxides, salts, carbohydrates and in virtually any other iron compound form by impregnation, insertion, or otherwise, into any suitable substrate to be used as a collection and/or collection medium, a sock or an oversock.

Impregnation may occur in a variety of ways, such as, for example, through absorption or chemical reaction with the substrate, or alternatively a substrate of cotton netting or twine could be treated or coloured with iron compounds such as oxides.

Similarly, a substrate made in accordance with the invention could be formed by encasing or partially encasing iron wire or pieces, or by encasing iron particles or flakes, i.e. a matrix. The perishability of the substrate and the rate at which iron is released to the local aquaculture environment may be matched to the function to be performed by the substrate, e.g. as a collection and/or growing medium, sock, oversock, etc. Alternatively, wire used within a collection and/or growing medium could be replaced with (for example) jute twine, which can absorb and retain any number of ferrous compounds. Whilst jute twine over a period of time decomposes, before total dispersement occurs the appropriate ecosystems would have been developed and iron would have become bio-available to mussels, together with accompanying benefits.

Iron compounds could be incorporated into any of a variety of substrates in accordance with the invention, including plastics products, such as the collection and/or growing medium described in the present applicants aforementioned International Patent Application No. PCT/AU2007/001890. The iron compound could be any suitable iron compound such as sulphides or ferrous oxides. Alternatively, plastic granules could be mixed with blowing agents such as bicarbonates, or any other suitable blowing agents available on the market, before the injection or the extrusion process of the substrate. The blowing agent serving to create aeration pores within the substrate that renders it more readily able to absorb the required iron compounds. The substrate could then be cooled in water that contains soluble iron salts or other suitable compounds. Alternatively, the plastic granules could be mixed with an agent that can induce a chemical reaction that is hot detrimental to the plastics substrate but permits iron to be present on the surface of the substrate.

Plastics products that incorporate iron as a colouring agent could serve to induce stronger byssal attachment to a plastic substrate formed therefrom as opposed to one which has no iron incorporated within.

When iron or iron compounds are entrapped within plastic substrates, it may appear that the iron source is unavailable. However, trials have indicated that this is not the case. It is presently hypothesised (but the invention is not limited by this theory) that chelating agents including some marine organisms can powerfully deal with iron atoms or ions on an individual basis. A substrate that utilises iron oxides as a colouring agent therefore potentially has millions of iron atoms on the surface of the substrate, sufficient to create beneficial effects to higher marine organisms and in particular the main colonisers.

Iron is not normally soluble and generally requires chelation in order to become available as a nutrient source for hydroids or other living organisms. In a marine environment, certain lower order marine organisms serve as the required chelating agents.

The provision of a relatively evenly distributed source of bio-available iron provided by way of a substrate made in accordance with invention assists mussel cultivation in many ways. For example, when collecting mussel spat the presence of iron can serve as a settlement cue for mussel larvae and its absence or diminished abundance can serve as a deterrent with regards to settlement. As the present invention is also based on the realisation that iron is required in order to stimulate the growth of strong mussel byssal treads and that its absence or diminished abundance can affect the strength of byssal securement to each other and in particular to a collection and/or growing medium. Hence, the provision of bio-available iron increases the foothold strength of the supporting mussels, and the strength of attachment of dependent mussels to the supporting mussels, reducing incidence and severity of the slide-off effect.

The provision of bio-available iron is particularly desirable when socking mussels during the declumping and grading phase of mussel cultivation. In accordance with a preferred aspect of the present invention, a perishable cotton netting, encasing twine, or any other suitable (preferably organic) substrate or combination of substrates, impregnated with iron compounds (or otherwise provided with a source of iron) may be provided for use in socking spat mussels. This permits the socking of very large spat which could lead to additional market opportunities as older, and therefore larger mussels, could be sold at premium prices. In the past, socking of large spat or small mussels was not possible using known cotton net socking systems as large spat or mussels are unable to develop sufficiently strong byssal attachment to growing mediums before the cotton net decomposes, resulting in crop loss. However, by utilising cotton socking material that has been impregnated with iron compounds (or otherwise provided with a source of iron) in accordance with the invention, mussels are provided with the urgently required iron that is needed to produce stronger byssal attachment.

After collecting spat mussels utilising a suitable collection and/or growing medium, the collected spat is stripped off the medium, declumped and graded before being socked onto a growing medium at a desired density suitable for re-introduction into the water. This phase of the cultivation process is quite brutal, and hence, traumatizing for the spat mussels as their byssal threads have been torn away in order to declump the spat in singular units suitable for socking.

When reintroduced into the water, it is the purpose of the mesh sock to retain the spat mussels in the direct vicinity of the growing medium until new byssal threads develop and attach securely to the growing medium. Hence, if the sock is perishable, the mussels only have a limited time to securely attach to the growing line before the sock disintegrates.

Mussel byssal thread development can vary, for example, smaller, or younger, spat mussels more readily develop new byssal threads than older spat mussels. For this reason, if harvest is to be improved, the sock material must retain the mussels on the growing line for as long as possible to ensure that as many mussels as possible have been able to secure themselves to the growing line before the sock perishes. A known way of achieving this aim has been to utilise a mussock socks made of thicker cotton fibres so that the decomposition process is slowed. However, thicker cotton socks are far more expensive than standard socks which obviously results in higher production costs. Aside from increasing costs, if thicker cotton socks are used, less sock material can be placed onto a cartridge for use in an automated socking process.

Instead of increasing the thickness of the socking material used, by utilising a sock that has been impregnated with iron (or otherwise contains a source of iron) in accordance with invention, the then bio-available iron source provided acts as a means of medication for the traumatized spat mussels at this crucial time, which results in faster healing, and in turn, enables the mussels to create strong byssal thread attachment to the growing line and/or other mussels. In fact, it has been found that the thickness of the socking material can be reduced as compared to standard socks due to the addition of the iron source, since mussels are able to create strong byssal threads faster by way of the bio-available iron source. To optimize the release of the iron, and hence, to more readily create a controlled bio-available iron source within the aquaculture environment that results in the desired medication for the mussels at the appropriate time, the decomposition rate of the sock (or other substrate) needs to be considered. That is, as the rate of decay of the sock or substrate is proportional to some degree of the iron source release, the selection of the substrate material is important.

In the case of cotton socks, or other preferred organic decomposable material socks or substrates, the time span of iron release is determined by the 'decay factor' of the substrate. This decay factor can be changed by varying the thickness of the organic strands used to construct the sock or substrate, i.e. thicker strands will take longer to decay than thinner strands.

It has been found that the decay properties of organic materials, such as cotton which is preferred, also assist in converting the iron compound into its bio available form. Hence, although plastics and other suitable materials can be used in accordance with the present invention, it is especially preferred to use an organic material impregnated with iron, or an iron compound, to perform the invention.

As such organic substrates release their iron source almost immediately, and only continue to do so until such time that the substrate has decomposed, in some aquaculture environments longer term iron provision may be required. In that case a sacrificial iron wire could be introduced simultaneously and longitudinally during the socking act. Hence, the ironised organic substrate would provide an immediate iron source, whilst the sacrifice wire would provide an iron source on a longer term basis.

It would be desirable to be able to oversock a collection and/or growing medium with an oversock (or substrate) that has been impregnated with iron, or contains a source of iron, in accordance with the invention. Such an oversock (substrate) containing an iron source would encourage healthier and more vigorous growth along the entire length of a growing medium as already described. However, as mentioned at the outset of this specification, this is a difficult process, particularly for continuous lines, utilising known oversocking apparatus and techniques - due mainly to the cartridgisation issues associated with known tubular oversocking materials.

Accordingly, and in accordance with a further aspect of the present invention, an improved oversocking apparatus and method is provided for applying an oversock substrate to a collection and/or growing medium. The improved oversocking apparatus and associated method being particularly suitable for applying an oversock substrate material containing a source or iron, but not being limited thereto. Hence, the improved oversocking apparatus and method of the present invention could be utilised to produce the oversocked collection and/or growing medium 320 shown in Figure 3. In Figures 4 to 10 there is shown various views and portions of an apparatus 500 for applying an oversock substrate to a collection and/or growing line, or medium 320, using a planar sheet sock material substrate 400, rather than a traditional tubular sock. As shown in Figure 5, this planar sheet substrate 400 may be provided on a roll 402, allowing for oversocking of continuous lines 320, as well as drop lines 320 ("droppers").

The oversocking substrate 400 could be a mesh substrate having square, rectangular, or diamond shaped mesh spaces (or any other suitable shape). The roll 402 of substrate 400 can be presented to the oversocking apparatus or machine 500 in any desired roll 402 length (e.g. 1000 or 2000 meters, etc). Planar sheet substrate 400 is fed from roll 402 past a tensioner 404 (see Figure 5).

In Figure 7, it can be seen that planer substrate 400, after passing tensioner 404, enters a first guide means 420, being a first circular orifice which has a diameter smaller than the width of planer substrate 400. In this way, planer substrate 400 is guided into a semi-tubular form 406 as it passes through first guide means 420 (i.e. the first orifice).

In Figure 8, it can be seen that downstream of first guide means 420 is a second guide means 430, which is a second circular orifice having a diameter smaller than the first orifice (i.e. first guide means 420). Semi-tubular substrate 406 is fed through second guide means 430 (e.g. the second orifice) to form a tubular oversock substrate 408. Some overlap of the edges of planer substrate 400 may occur in tubular oversock form 408, depending on the width of planer substrate 400, and the diameter of the growing and/or collection line 320 being oversocked.

Referring back to Figure 7, it can be seen that collection and/or growing line 320 is also passed through first and second guide means 420,430, simultaneously with planer substrate 400. In this way, collection and/or growing line 320 becomes encircled or encased by planer substrate 400 as it is guided into semi-tubular form 406, and then tubular oversock form 408, as previously described.

Hence, collection and/or growing line 320 can be continuously processed and oversocked, regardless of its length. This is because the oversock substrate 400 is not supplied as a pre-made tube. When planer oversock material 400, on roll 402, is fully fed through, a new roll (402) can be substituted without needing to cut the collection and/or growing line 320. A tubular oversock (not shown), supplied on a tubular cartridge (not shown), must pass over an end of a collection and/or growing line before the sock can be applied to that line — hence, cartridges can only be changed when starting to feed a new line. By supplying an oversock substrate 400 in flat or planar form (preferably as a continuous roll 402), the roll 402 can be changed at any time even where the line 320 is a long continuous line 320, as the tubular sock is built up around the line 320 during operation of oversocking apparatus 500. Furthermore, the roll 402 may contain many more metres of oversocking substrate 400 than a cartridge, and hence is space and time efficient for use on a marine vessel.

Oversocking apparatus 500 is designed to perform the oversocking operation without loading a collection and/or growing line 320 onto the deck of a vessel, although the line 320 could be put onto the deck if desired for any reason. In use, a portion of the oversocking apparatus 500 supporting the first and second guide means 420,430, preferably extends over the side of a vessel. In this way, a long-line (item 160 in Figure 2) supporting a collection and/or growing line 320 may be raised to the side of the vessel just beneath the protruding oversocking apparatus 500, but sufficiently clear of the protrusion in order to permit the collection and/or growing line 320 to be detached from the long line (160) and raised through the guide means (420,430) supported on the protruding portion of the apparatus 500. The long-line (160) may be placed on rollers (not shown) attached to the vessel on either side of the machine 500. These rollers could be mechanised and designed to move along the long-line (160) at a speed that is appropriate for the oversocking machine 500 (production speed). Apparatus 500 may draw the collection and/or growing line 320 through the guide means (not shown) whilst encasing or oversocking the collection and/or growing line 320 with planer substrate 400 as described above.

One operator could detach an end of the drop line 320, or a continuous collection and/or growing line 320, at the right time and then continue the detachment process at the required rate. Another operator on the other side of the machine 500 could re-attach the now oversocked line 320 to the long-line (160). This process could be assisted by a draw wheel 440, as shown in Figures 4 and 10, which is matched appropriately to the rollers (not shown).

An oversocked collection and/or growing line 320 could be drawn from the water and fed or pulled through the guides 420,430 by way of a motorised draw wheel 440. The line 320 would pass over the draw wheel 440 and could be re-attached to the long line (160) and returned to the water.

As the now oversocked line 320 exits the second orifice 430, it is necessary to ensure that the tubular oversock 408 is maintained in tubular form. In the embodiment shown, this is accomplished by binding the oversocked line 320 with an appropriate linear strand, or string such as twine (which could also be an ironised substrate in accordance with the invention), using the desired tension and pitch.

As shown in Figures 7 and 9, a binding mechanism 460 may be positioned downstream from second guide means 430 (i.e. the second orifice). This binding mechanism 460 is an annular ring which is belt driven by a motor 462 and held in position relative to first and second guides 420,430, by rollers 464. Binding mechanism 460 supports a turret 470 used to wrap the linear strand 480 around oversocked line 320. Twine 480 is dispensed from a spool 482 also mounted on the ring 460. As the ring 460 is rotated relative to guides 420,430, and collection and/or growing line 320, twine 480 is dispensed to secure the oversock substrate 400 into its tubular form 408. Appropriate tensioning may be obtained by the use of a tensioner or resisting element (not shown) on or adjacent the spool or turret 470. The twine 480 may be perishable or non-perishable, and may be iron impregnated (as already mentioned), to hence itself be a substrate for use as a collection and/or growing aid. The pitch of the twine 480 binding could be determined by the r.p.m of the rotating ring 460, and the rate at which collection and/or growing line 320 is drawn (fed) by draw wheel 440 (i.e. the draw rate).

In an alternative embodiment (not shown) the binding mechanism could be mounted on or attached to the second guide means, or orifice, the binding mechanism and second orifice rotating relative to the collection and/or growing line 320. This binding could also be achieved by ensocking the mesh in perishable cotton netting. Even though cotton netting requires cartridgeization, up to 1000 or so meters could be placed on a cartridge (unlike the tubular non perishable diamond shaped netting that previously has been used for the oversocking operation - as due to the nature of this tubular oversocking net, comparatively very little net could be placed on a given cartridge).

Use of a perishable binding (whether thread or cotton sock) still serves to keep the oversock bound long enough for mussel byssal threads to attach to the oversock substrate and keep it in a bound position. Mussels then grow though the oversock 400, but the structure significantly reduces the "slide-off effect".

The two different sized orifices (first and second guide means 420,430) provide a funnel like effect for the planer oversock substrate 400 which permits for total encirclement of the line 320 by the oversock 400 before binding. The mesh spool rotates in a controlled manner or freely rotates. It is preferably designed so as the mesh (substrate 400) entered the first orifice 420 (i.e. the lower and larger one) from beneath, and at an appropriate angle so as to permit the line 320 to be drawn into this first orifice 420 without impediment from the mesh substrate 400. Although the embodiment shown uses two separate rings to form first and second orifices (420,430), a funnel (not shown) could be substituted for the rings (420,430) and would work in the same manner.

Alternatively, the binding mechanism 460 could be used at an appropriate pitch to entwine wire (or a line) around a collection and/or growing medium 320, without the presence of a mesh oversock (i.e. substrate 400). That is, the wire or line would form the 'oversock' to encase the collection and/or growing medium 320. The present invention therefore provides improved mussel farming apparatus and methods that can be utilised to: increase spat collection yield; improve even density distributions on a collection and/or growing line; and/or, improve mussel byssal attachment to a collection and/or growing line leading to an increased harvest. An improved oversocking apparatus and associated method is also provided that enables an oversocking material to be applied to a collection and/or growing line in an easy manner.

While this invention has been described in connection with specific embodiments thereof, it will be understood that it is capable of further modification(s). The present invention is intended to cover any variations, uses or adaptations of the invention following in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains and as may be applied to the essential features hereinbefore set forth.

Finally, as the present invention may be embodied in several forms without departing from the spirit of the essential characteristics of the invention, it should be understood that the above described embodiments are not to limit the present invention unless otherwise specified, but rather should be construed broadly within the spirit and scope of the invention as defined in the appended claims. Various modifications and equivalent arrangements are intended to be included within the spirit and scope of the invention and the appended claims. Therefore, the specific embodiments are to be understood to be illustrative of the many ways in which the principles of the present invention may be practiced.

Claims

CLAIMS:

1. An organic or plasties material aquaculture substrate or medium for use with or as a mollusc collection and/or growing aid, sock or oversock, the aquaculture substrate or medium including a source of iron that is provided within or on the surface of the substrate or medium.

2. The substrate or medium according to claim 1, wherein the substrate or medium is a cotton sock that has been impregnated with iron, or an iron compound.

3. The substrate or medium according to claim 1 , wherein the substrate or medium is a cotton sock that includes strands of twine or yarn that has been impregnated with iron, or an iron compound.

4. The substrate or medium according to claim 2 or claim 3, further including an additional source of iron provided by way of the provision of a sacrificial linear strand containing iron, or an iron compound.

5. The substrate or medium according to claim 1 , wherein the substrate or medium is a plastics material collection and/or growing line or aid that has had an iron compound introduced therein during the plastics extrusion or molding process.

6. The substrate or medium according to claim 5, wherein the iron compound introduced therein during the plastics extrusion or molding process is an iron oxide colouring agent.

7. The substrate or medium according to claim 1 , wherein the substrate or medium is a plastics material collection and/or growing line or aid that has been coated with a substance containing a source of iron.

8. The substrate or medium according to claim 7, wherein the substance containing a source of iron is an iron oxide or iron solution.

9. The substrate or medium according to any one of claims 5 to 8, further including an additional source of iron provided by way of the provision of a sacrificial linear strand containing iron, or an iron compound.

10. The substrate or medium according to any one of claims 1 to 4, wherein the substrate or medium is decomposable or perishable.

11. A mussel cultivation method including the steps of: collecting spat mussels utilising a collection medium that is suspended in a body of water; declumping and/or grading the collected spat mussels; and, socking the collected spat mussels onto a growing medium utilising an organic material sock that contains a source of iron.

12. The mussel cultivation method according to claim 11, wherein said organic material sock that contains a source of iron is a cotton sock that has been impregnated with iron or an iron compound.

13. The mussel cultivation method according to claim 11 or claim 12, wherein the collection and/or growing medium also includes a source of iron.

14. An apparatus for applying an oversock produced from a planar aquaculture substrate to a collection and/or growing line, said apparatus including: a first guide means through which said collection and/or growing line and said planar aquaculture substrate are fed, said first guide means guiding said planar aquaculture substrate into a semi-tubular form around said collection and/or growing line; and, a second guide means located downstream of said first guide means through which said collection and/or growing line and said semi- tubular substrate are fed, said second guide means guiding said semi-tubular substrate into a tubular oversock, encasing said collection and/or growing line inside said oversock.

15. The apparatus according to claim 14, wherein said first guide means is a circular orifice and said second guide means is a circular orifice having a smaller diameter than said first circular orifice.

16. The apparatus according to claim 14 or claim 15, further including a binding mechanism for applying a binding means to said oversock.

17. The apparatus according to claim 16, wherein said binding mechanism is a cartridge housing and said binding means is a cotton sock.

18. The apparatus according to claim 16, wherein said binding means is a linear strand and said binding mechanism is a turret located downstream of said second guide means, said turret rotatable about the oversocked collection and/or growing line whereby said linear strand fed through said turret is wrapped about the oversocked collection and/or growing line.

19. The apparatus according to any one of claims 14 to 18, wherein said aquaculture substrate includes a source of iron.

20. The apparatus according to claim 17, wherein said cotton sock is impregnated with iron, or an iron compound.

21. The apparatus according to claim 18, wherein said linear strand includes a source of iron, or an iron compound.

22. A method for applying an oversock to a collection and/or growing line, said method including the steps of: feeding a planar aquaculture substrate and said collection and/or growing line through a first guide means, said first guide means guiding said planar aquaculture substrate into a semi-tubular form around said collection and/or growing line; and, feeding said collection and/or growing line and the semi-tubular substrate through a second guide means, said second guide means guiding the semi-tubular substrate into a tubular oversock; whereby said collection and/or growing line is encased inside said oversock.

23. The method according to claim 22, further including the step of: applying a binding means to said oversock.

24. The method according to claim 22 or claim 23, wherein said aquaculture substrate includes a source of iron.

25. The method according to claim 23, wherein said binding means is a cotton sock which is impregnated with iron, or an iron compound.

26. The method according to claim 23, wherein said binding means is a linear strand which includes a source of iron, or an iron compound.

27. A mollusc produced through use of an aquaculture substrate, apparatus or method according to any one of the preceding claims.

28. Use of an aquaculture substrate according to any one of claims 1 to 10, for collecting and/or growing mussels.