JP4493419B2 - Aquaculture net, installation method, disposal method - Google Patents

Description

  The present invention relates to an aquaculture net, an installation method thereof, and a disposal method thereof, and more particularly to an aquaculture net used for breeding and culturing shellfish and algae in tidal flats and shallow fields, an installation method thereof, and a disposal method thereof It is.

Shellfish and algae live in the natural environment of tidal flats and shallow areas, and fishermen have benefited greatly.
However, in recent years, drowning has occurred, algae has not grown well, and the yield of fish has drastically decreased. Therefore, the fishery has been converted from a fishery that can be raised to a fishery that can be nurtured, and is now moving to an ocean farm. The same applies to shellfish (for example, Patent Document 1). Shellfish have also been lost from fishing grounds due to tides, shellfish ecological activities, human and wild bird damage, and yields have decreased. There is a problem that the ecology of shellfish must be protected, yield must be secured and the environment must be preserved.
JP 2000-175590 A

  The present invention has been made in view of such a situation, and aquaculture net, an installation method thereof, and its environmental protection while preventing the movement and loss based on ecological activities such as shellfish and increasing the yield. The object is to provide a disposal method.

In order to achieve the above object, the aquaculture net of the present invention is composed of polylactic acid fibers having no core-sheath structure, and is spread and fixed in a tidal flat or a shallow area, and has a mesh size of 10 mm to 30 mm. The intersection of the warp and weft of the mesh is not heat-sealed, and the surface is not coated with a resin, and the intersection strength is 50 N or more.

According to the present invention, it is preferable that the aquaculture net is a Russell net or a knotless net.
In the method for installing the aquaculture net of the present invention, the aquaculture net is spread and fixed on a tidal flat or a shallow area where shellfish to be cultivated exist.

The method for disposing of the aquaculture net according to the present invention is a method in which the used net after using the aquaculture net is decomposed and disappeared by hydrolysis and / or microbial treatment.
According to the present invention, in the above, it is preferable to decompose and disappear using a composting device having a function of adjusting temperature, moisture and pH.

That is, the aquaculture net of the present invention is used in aquaculture farms such as shellfish, and is discarded after achieving a desired purpose. Because it is composed of biodegradable polylactic acid fiber, even if it is lost due to a disaster or accident before it is discarded, it will naturally disappear without any impact on the global environment and decompose into CO ₂ and H ₂ O Is done.

  For disposal, prepare a composting device with temperature, moisture, and pH control functions, install this composting device by burying it on the beach, etc., and put in a net with dirt substances such as algae and shellfish attached Then, it decomposes and disappears in a short period of time, and processes so as not to give a load to the coastal nature.

Hereinafter, the present invention will be described in detail.
The aquaculture net for shellfish of the present invention is mainly made of polylactic acid fiber having biodegradability. For this reason, it retains its form during use in tidal flats and shallow areas, but after use for a certain period of time, it has a feature that it returns to nature by hydrolysis and enzymatic degradation by microorganisms. Compared to a net made of natural fibers having biodegradability, it is lightweight despite having the necessary strength, and a uniform net can be manufactured at low cost. Moreover, it is more resistant to seaside ultraviolet rays and ozone than a net made of natural fibers. For example, in the case of a net made of natural fibers, it deteriorates in about three months and the desired physical properties cannot be obtained.

  The aquaculture net of the present invention is formed by a Russell net, a no-intersection network generally referred to as a no-node network, a knotted cocoon net, or the like. The Russell net is a net produced by knitting with a known knitting machine. A knotted cocoon net is a net in which the intersection has a knot and the shape of the knot is similar to that of a cocoon. The knotless net is a net obtained by forming a rhombus net repeatedly by twisting a yarn using a knotless knit netting machine.

  The size of the mesh differs depending on, for example, the type of shellfish to be cultured. In general, there are varieties, oysters, clams, clams, clams, scallops, stupids, etc. in the tidal flats and shallow areas, so that they do not disappear from the farm, that is, to avoid escape through the mesh. Is preferably in the range of 10 mm to 30 mm. In this case, the scale refers to the size of the net space in the longitudinal direction and the weft direction. The aquaculture net of the present invention prevents shells from escaping in tidal flats and shallow areas, and does not prevent activity in tidal flats. If the mesh size is 10 mm or less, there is a possibility of hindering activity during growth. If the mesh exceeds 30 mm, the grown shellfish escape and the yield is significantly reduced. By using the net, it is possible to prevent bird damage caused by wild birds catching shellfish.

  In order to ensure the practical strength of the net, the strength of the polylactic acid fiber to be used is preferably 3.0 cN / dtex or more, and any of multifilament, spun yarn (spun yarn), and monofilament may be used. Multifilament is better than verticality. If the fineness is 280 dtex to 1650 dtex, desired strength and other physical properties can be obtained.

  As for the physical properties of the net, it is important that the handling properties at the time of installation and the like are good, and it is enough to withstand tides and waves. In general, the intersection point has a lower strength than the net yarn portion, but the intersection point strength needs to be 50 N or more. If it is less than that, there is a risk that the fiber will break due to friction caused by a person moving on or receiving waves or tides. The intersection strength of the net of the present invention needs to be 50 N or more in both the warp direction and the weft direction, and is preferably 100 N or more. However, the warp direction and the weft direction need not be equal.

  In the present invention, this intersection strength is expressed by the strength measured according to the tensile strength test of the mesh yarn of JIS A8960. That is, instead of “net yarn” in JIS A8960, “intersection of mesh yarns” is measured. Specifically, according to JIS A8960, a mesh thread having an intersection point is correctly attached to the upper grip as a test piece, and the other end of the test piece is attached to the lower grip so that there is no unnatural slack in the test piece. The intersection strength is obtained by measuring the tensile strength of a straight line with a gripping interval of 20 cm and a tensile speed of 20 cm / min. Except for the above, measurements are performed by performing tests as described in JIS A8960. In addition, since the strength of the intersection is generally lower than that of the net yarn portion as described above, the strength of the intersection can be obtained in this way.

  The net with the above configuration is tailored to the desired size, and the rhombus is tailored and placed on tidal flats, shallow fields, and the surface of the water. Protect and grow shellfish. If necessary, bonding can be performed using a binding string having biodegradability. In addition, it is fixed to the ground using a biodegradable anchor material made of a biodegradable resin or a natural material such as a bamboo stick.

  In other words, the biodegradable aquaculture net of the present invention is formed in advance in a factory to a specified size, for example, about 10 m × 30 m, and an edge rope is passed through it, and the net and the edge rope are integrated using a thin twisted yarn. It is processed into square tailoring. This net is brought into the aquaculture site, spread and laid, and fixed to the ground with anchor material. If necessary, the installation range can be clarified by setting up a pole or attaching a float. In some cases, it may be temporarily installed using a sandbag or the like. In this case, each member is preferably made of a biodegradable resin raw material (polylactic acid).

In this way, processing of nets that are used for aquaculture of shellfish, algae, etc., and that need to be discarded after achieving a desired purpose will be described. Used nets are attached to tidal flats, microorganisms living in shallow water, shellfish, and algae. For this reason, when it is left on the beach, it decomposes and generates gas such as hydrogen sulfide and mercaptan, which causes bad odor. In addition, the nets become huge garbage, that is, industrial waste, and if left untreated, the beach landscape will be significantly impaired. However, since the net of the present invention is composed of polylactic acid fibers, a composting device having a function of adjusting temperature, moisture and pH and, if necessary, a deodorizing function can be embedded in the vicinity of the beach, beach, etc. By installing and disposing of the used net into the composting apparatus and decomposing and disappearing, it can be converted into CO ₂ and H ₂ O and discarded so as not to give a load naturally. In addition, even if a net flows out due to an accident, disaster, etc., it is naturally decomposed and converted into a substance that exists in nature, so it is an environmentally friendly net member.

Polylactic acid is hydrolyzed by direct polymerization of lactic acid or by polymerization of lactide obtained by cyclization reaction using lactic acid obtained by fermenting starch and saccharides made from corn and the like as raw materials. A high molecular weight polylactic acid, which is a type of resin, can be melt-spun and drawn into a fiber material having sufficient strength. If necessary, an original yarn can be produced and used. Then, as described above, hydrolysis and enzymatic degradation by microorganisms occur, and the decomposed lactic acid becomes CO ₂ and H ₂ O.

[Example]
Using 6 polylactic acid fibers 1100 dtex / 192fil with a relative viscosity of 2.00 and a strength of 4.0 cN / dtex, a net network with a mesh size of 15 mm and a hook of 100 was created by a knotless knitting machine. The intersection strength of the net was 120N. And this meshwork is tailored with an edge rope (polylactic acid rope, diameter 6 mm) and an overlock thread (polylactic acid twisted thread, diameter 2.5 mm) so as to have a size of 10 m × 30 m, and shellfish A net for aquaculture. This net was spread and laid on the aquaculture tidal flat, and fixed using anchor pins. Further, binding of 10 m × 30 m netting was performed using a binding string formed of a polylactic acid rope having a diameter of 3 mm.

  As a result of a one-year demonstration experiment, the yield was about 150% compared to the place where the net was not used. There was no change in the size of the net compared to when it was laid. Although the net intersection strength after the experiment was reduced to 90 N, there was no problem in handling.

  The net after use was accompanied by mud flats and organisms, producing a strange odor. This net is collected in a wet state and cut to a size that can be easily treated with scissors. / Day) and treated at a temperature of 58 ° C. for 3 weeks. As a result, there was almost no residue and it was fully decomposed.

[Comparative example]
Using eight cotton yarns having a strength of 1.3 cN / dtex (equivalent to 1100 dtex), a net network having a mesh size of 15 mm and a hook of 100 was created using a knotless knitting machine in the same manner as in the above-described example. The intersection strength of the net was 51N. And this meshwork is made into squares using edge ropes (cotton rope, diameter 6 mm) and overlock yarn (cotton yarn twist, diameter 2.5 mm) so as to have a size of 10 m × 30 m. A net for shellfish farming. The net of this comparative example was spread and laid on an aquaculture tidal flat, and fixed using anchor pins.

  As a result of the demonstration experiment, in 3 months, the intersection strength of the net was lowered to 10 to 20 N where the shape could be maintained and measured. In addition, the net size was wide or narrow, and there were many cuts. For this reason, the performance required for shellfish farming, that is, the yield, was not different from the case where no net was used. As the intersection strength decreased, part of the net separated and floated on the tidal flat, and the seaside landscape was damaged.

Claims (5)

It is composed of polylactic acid fibers that do not have a core-sheath structure, and is spread and fixed in a tidal flat or shallow place. The mesh is 10 mm to 30 mm, and the intersection of the warp and weft of the mesh is heat- sealed. An aquaculture net characterized in that the surface is not coated with a resin and has an intersection strength of 50 N or more.   The aquaculture net according to claim 1, which is a Russell net or a knotless net.   A method for installing an aquaculture net, wherein the aquaculture net according to claim 1 or 2 is spread and fixed on a tidal flat or a shallow place where shellfish to be cultivated exist.   A method for disposing of an aquaculture net, comprising: decomposing and erasing a spent net after using the aquaculture net according to claim 1 by hydrolysis and / or microbial treatment.   5. The method for disposing of aquaculture nets according to claim 4, wherein the decomposition and disappearance is performed using a composting device having a function of adjusting temperature, moisture and pH.