The invention relates to netting. More particularly, the invention relates to netting for a seine for use in a cage for the farming of fish.

For the farming of fish in seawater and fresh water, enclosures of various kinds are used, hereafter called a cage. The cage provides for the farmed fish to be kept within a limited area. For such cages, seines may be used. The cages may be divided into at least two main types : several cages may be connected to a floating stage of steel; the cages may lie one by one. Cages that are connected by a floating stage of steel are often termed a steel farm. The floating stages are provided with buoyancy bodies and the seine of the cage is secured to the floating stages. Cages that lie one by one are provided with one or more concentric plastic rings which form the buoyancy body of the cage. The seine is secured to the plastic ring.

The mesh of the seine is selected on the basis of two conditions. The mesh must be small enough for the farmed fish not to be able to swim out of the cage through the meshes . The mesh must be large enough for there to be good flow of water. Good flow of water ensures that the fish will get enough oxygen. The material forming a seine will be referred to as netting here. Netting that is submerged in water, especially in sea- water, will be colonized on its surface by microscopic and macroscopic organisms. Macroscopic organisms may be algae, mussels, barnacles and sea squirts / hydroids . As these organisms increase in number and grow, fouling will arise on the seine. This reduces the effective size of the mesh openings and reduces the water flow. The fouling will also weigh the seine down so that the buoyancy bodies of the cage will have to be dimensioned in proportion to the increased weight. The seine will also constitute a greater resistance to water currents, and the mooring systems of the cage must be dimensioned in proportion to this. Untreated seines should be replaced after about 3 months, before the fouling of the netting becomes too extensive.

A known way of fighting fouling or reducing the rate of fouling is to impregnate the seine with a biocide. Examples of known biocides are copper-containing biocides. Copper is considered to be an environmental poison and it is desirable to reduce the use of copper compounds as much as possible. Copper-impregnated seines will liberate copper into the seawater by bleeding. This is a diffuse emission of copper. Studies indicate that bleeding may constitute 80-90 % of the copper emissions from the fish farming industry. Impregnated seines may remain in the sea for one season, for about 9 months that is to say, before they are so fouled that they must be cleaned. The seine is then taken ashore and washed in large washing machines. This may be carried out in connection with each fish farming facility. The washing removes fouling from the seines but also causes more copper to bleed from the seines. Thereby the seine washing facilities constitute copper emission points. In some countries, the authorities demand that there should be no emission of copper from seine washing. Therefore, the seme washing facilities have been gathered into larger units which have made the necessary investments to meet official requirements. This has entailed that seines that are to be washed must be transported farthe than before to central seine washing facilities. This entails, in turn, that the farming facilities must have more seines than before as the circulation time of the seines has beeome 1onger .

Seines, and particularly seines with fouling, weigh several tonnes, depending on the size of the cage. The retrieval of seines from the sea onto a vessel, lifting from the vessel onto the shore, loading and unloading onto/from a road vehicle for transport to a seine washing facility, handling at the seine washing facility, inspection, impregnation and dry ing, transport back to the farming facility, storing and deployment into the sea will amount to between 15 and 20 lifting operations. Each lifting operation involves a risk of a hole being torn in the seine. Washing at central seine washing facilities also represents a risk of viral and bacterial diseases being spread.

Thus, there is a need for a seine for use in a cage, which i formed by netting that does not foul as quickly as the netting known today. In particular, there is a need for netting which may remain just as long in the sea without the use of impregnating agents as the netting with impregnating agents known today. Thereby the seine may be washed in connection with the local farming facility, which entails that the number of lifts may be reduced, the transportation costs and im pregnation costs are reduced or eliminated and the risk of infection is reduced. Further, scrapped seines may be disposed of without being treated as special waste, in contrast to copper- impregnated seines which count as special waste. It is known within the art that a number of monofilament fibres are twisted or laid to the left into a so-called yarn. Thus, the yarn is a twisted multifilament. Several yarns are laid to the right into a so-called string or strand. Three strands are laid to the left into a so-called hawser, forming a three-ply hawser then. Several hawsers may be laid to the right into a cable. It is also known that a four-ply hawser is formed by four strands, one strand forming a core, a so- called heart. It is further known that hawsers, for example, may be formed by more than four strands . The above does not constitute a full presentation of this discipline. There are also known examples of the lay direction deviating from what has been described here.

The use of monofilament fibres is known from fishing nets as well. In contrast to a seine, a fishing net is arranged to catch fish by holding the fish entangled in the meshes. It is known to produce fishing nets from threads formed by one thread, so-called monofilament fishing nets. It is further known to produce fishing nets from so-called monotwine . The patent document JP 1014355 discloses a fishing net formed by two filaments that are twisted around each other into one thread, threads crossing each other two by two and being held fixed to each other in a knotless manner by the filaments being twisted around each other and in such a way that the two filaments of one thread continue in separate directions in separate threads after the entwining. The patent document JP 1097251 discloses the same for three filaments that have been twisted around each other into one thread. After the entwine- ment of two threads into a knotless connection, one filament of one thread continues in another direction in a different thread from the two other filaments of the thread.

It is also known to produce fishing nets from so-called mul- timono twine. By multimono are meant two or more monofilaments that have not been twisted together. In fishing nets the multimono twine is normally formed by 6 or 8 monofilaments .

By a bundle is meant, in what follows, one or more monofilaments. When the bundle is formed by two or more monofilaments, the monofilaments are not twisted around each other. Thus, in bundles formed by two or more monofilaments, the monofilaments will lie, in the main, side by side in the bundle. The monofilaments of the bundle may intersect where the bundle is bent into loops, as when one or more bundles are crocheted .

By a thread are meant, in what follows, a yarn,

string/strand, hawser and cable as these are described above.

Knotless netting may be produced by twisting two or more threads, as disclosed in the patent documents JP1014355 and JP 1097351. Knotless netting may also be produced by braiding several threads or by crocheting several threads, so-called raschel knitting. The patent documents US 3,866,512 and SU 383764 disclose how knotless netting may be formed by braiding. Several threads are braided into one bar. At regular intervals, a first bar is entwined with a first adjacent bar into a mesh joint and, at further regular intervals, the first bar is entwined with a second adjacent bar into a mesh joint, so that the entwinements with the first adjacent bar and the second adjacent bar alternate. In this way the meshes of the netting are formed.

Raschel -knitted or crocheted netting has the advantage over braided netting and twisted netting of being more resistant to running. Raschel-knitted netting is therefore what is normally used when cages for farmed fish are formed. Raschel- knitted netting has good tensile strength. In raschel -knitted netting, the bars are formed by at least three threads.

The invention has for its object to remedy or reduce at least one of the drawbacks of the prior art or at least provide a useful alternative to the prior art.

The object is achieved through features which are specified in the description below and in the claims that follow.

The invention relates to the forming of bars in netting.

The invention exploits the fact that known monofilaments have a smooth surface. For example, a monofilament in the form of a fishing line, known per se, will slowly become fouled if left lying in water or seawater. The fouling can easily be removed by wiping the smooth surface of the monofilament.

Surprisingly, it has turned out that by replacing the conventional thread with a bundle of monofilaments when forming the bar of the netting, netting that fouls more slowly than netting produced from thread is obtained. Monofilaments presenting a smooth surface are particularly advantageous. The netting may be produced by braiding at least three bundles by a braiding method known per se, or the netting may be produced by crocheting at least three bundles by a raschel knitting method known per se.

In a first aspect, the invention relates to knotless netting formed with bars and mesh joints, the bars of the netting comprising bundles formed by one or more non-twisted monofilaments. This has the advantage of the netting presenting a fouling-resistant surface.

In an alternative embodiment, one bundle may be formed by at least two monofilaments. The netting may be formed by at least three braided bundles. In an alternative embodiment, the netting may be formed by at least three raschel-knitted bundles. In a further alternative embodiment, the netting may be formed by twisted bundles, each bundle comprising at least two monofilaments.

In a second aspect, the invention comprises a method of producing knotless netting with bars and mesh joints, the method including the use of bundles formed by at least one or more non-twisted monofilaments on a braiding machine or crocheting machine which is arranged to twist, braid or crochet netting.

In an alternative embodiment, the method includes using bundles formed by two or more non-twisted monofilaments on a braiding machine or a crocheting machine which is arranged to twist, braid or crochet netting.

In a third aspect, the invention includes using knotless netting formed with bars and mesh joints to form a cage, the bars of the netting comprising bundles of non-twisted monofilaments. The cage is particularly suitable for use when farming fish in seawater and in fresh water.

In what follows, an example of a preferred embodiment is described, which is visualized in the accompanying drawings, in which :

Figure 1 shows a section of braided netting as it is described in the patent document SU 383764, but in which the netting has been produced in accordance with the invention, an enlarged detail of the bar of the netting and, on yet a larger scale, a section of a bundle included in the bar of the netting; and Figure 2 shows a section of raschel-crocheted netting produced in accordance with the invention, an enlarged detail of the bar of the netting and, on yet a larger scale, a section of a bundle included in the bar of the netting.

In the figures, the reference numeral 1 indicates knotless netting in accordance with the invention. Figure 1 shows knotless braided netting 1 as it is described in the patent document SU 383764, but produced in accordance with the invention. In figure 1, the bar 2 is formed by bundles 21-24 and the bar 2' by bundles 25-28. The bars 2, 2' are joined together at a mesh joint 4.

The bundles 21-28 are formed by monofilament threads 3 as it is shown for the bundle 24 in the enlarged section. As shown in figure 1, the monofilaments 3 lie substantially side by side without being twisted or spun around each other.

Figure 2 shows raschel-crocheted netting 1 as it is known within the art, but produced in accordance with the invention. In figure 2, the bars 2, 2' are formed by bundles 21-23 and bundles 25-27, respectively. The bundles 21-23, 25-27 are formed by monofilament threads 3 as it is shown for the bundle 22. As shown in figure 2, the monofilaments 3 lie substantially side by side without having been twisted or spun around each other.

The number of monofilaments 3 forming a bundle 21-28 is shown by seven monofilaments in figure 1 and by four monofilaments in figure 2. In alternative exemplary embodiments, the number of monofilaments 3 in a bundle 21-28 my be constituted by one monofilament 3, alternatively two monofilaments 3, alternatively three monofilaments 3, alternatively five monofilaments 3, or alternatively six monofilaments 3. The person skilled in the art will understand that even a larger number of monofilaments 3 than seven in one bundle is possible.

Example

Netting 1 was produced from monofilaments 3 formed from ny- Ion. The monofilaments 3 had a diameter of 0.35 mm. Seven monofilaments 3 were arranged into one bundle 21-23, 25-27. The netting was produced by raschel -knitting or crocheting three bundles 21-23 into one bar 2 and crocheting three bundles 25-27 into one bar 2'. The meshes of the netting 1 were formed by crocheting the bars 2, 2' together into a mesh joint 4 in a manner known per se. The bars 2, 2' had a diameter of 3.0 mm. The bar length was 23 mm, the mesh length was 43.5 mm and the mesh width was 36 mm.