JP4966218B2 - Polyp killing method by bubble cushion sheet coating - Google Patents

Description

  The present invention relates to a method for easily and inexpensively killing a polyp, which is a generation of jellyfish, by covering the polyp with a foam cushioning sheet at the site of the formation to prevent exchange of seawater around the polyp.

  A jellyfish is an animal belonging to a cnidarian (or a coelenterate). It is known that many of the relatively large jellyfish whose umbrella diameter grows to more than a dozen centimeters, for example, the moon jellyfish, changes between a floating jellyfish generation and an epiphytic polyp generation during its lifetime. The outline of the life history is as follows (see FIG. 4). In other words, fertilized eggs of jellyfish are generated and become cilia-like, almost spherical planula larvae, which transform into an appropriate base and become polyps. Polyps multiply asexually by division, budding, etc. to form colonies. In these polyps, a large number of lateral constrictions occur in the body part due to a change in conditions such as a decrease in water temperature, forming a striated body (strobila). When each constriction of this cuboid is constricted, a large number of Efila larvae are released asexually and start swimming. These Efila larvae produce a gastric canal system and tentacles during swimming life, and the agar layer develops and transforms and grows to become a jellyfish adult.

  These jellyfish adults often come in large quantities near the intakes of seawater utilization plants such as thermal power plants and nuclear power plants, preventing the seawater intake of seawater utilization plants. The seawater intake failure caused by the mass invasion of such jellyfish adults causes extremely serious damage such as deterioration of equipment performance, reduction of power generation output, water intake and power generation stoppage. Also, jellyfish adults often attack fishery facilities in large quantities. In this case, the adult jellyfish enters a fishing net such as a stationary net, and causes damage such as suffocation, death, quality degradation, and damage to the fishing net of fish in the fishing net.

  As countermeasures against damage caused by such a large amount of jellyfish adults, monitoring of the appearance of jellyfish adults, installation of jellyfish adult prevention nets in front of seawater intakes, recovery of jellyfish adults by ship, manpower, and screen, prediction of jellyfish adult attacks Various measures have been taken, such as the early implementation of measures. However, these countermeasures are all countermeasures against jellyfish adults, and no countermeasures have been taken against polyps that are the source of jellyfish adults.

  On the other hand, it is known that the regeneration ability of polyps, which are the generation of jellyfish, is extremely strong. Therefore, when killing polyps, it is considered difficult to completely prevent the generation of adult jellyfish from the polyps unless the polyp tissues / cells are sufficiently killed.

  In this regard, the present inventors have proposed in Patent Document 1 a method for effectively killing a polyp by exposing the polyp to water, air having a salt concentration of 5 ‰ or less, or high-temperature water having a temperature of 50 ° C or higher. However, when these methods are carried out at the actual place of polyps, it is necessary to inject fresh water or hot water and to carry out air bubbling for a long period of time, which requires complicated equipment and associated high costs. Therefore, there is a risk of lack of practicality. Thus, there is still a need for a suitable method for killing polyps at their actual place of birth simply and inexpensively.

JP 2004-275028 A

  The present invention was devised in view of the current state of the prior art, and its purpose is to provide a suitable method for killing jellyfish polyps at their actual place of attachment easily and inexpensively.

  In order to achieve the above-mentioned object, the present inventors diligently studied a simple and inexpensive method for killing polyps, and as a result, if the exchange of the seawater around the polyps is hindered, the polyps cannot take food and cannot breathe. It has been found that a bubble buffer sheet having a large buoyancy and flexibility is particularly suitable as a means for preventing the exchange of seawater, and the present invention has been completed.

  That is, the present invention is characterized in that the seawater contact area on the lower surface of the structure existing on the sea surface where the jellyfish polyp is deposited is covered with a bubble buffer sheet to prevent the exchange of seawater around the polyp. This is how polyps are killed.

  According to one preferred embodiment of the invention, the coating with the foam cushioning sheet is carried out for at least one month. According to another preferred embodiment of the invention, the foam cushioning sheet is formed from a biodegradable plastic. According to a particularly preferred embodiment of the present invention, the seawater contact area where the polyp is deposited is the lower surface of the floating jetty or the lower surface of the overhang of the breakwater.

  According to the method of the present invention, a polyp can be killed simply by covering the place where the polyp is deposited with a bubble cushioning sheet and preventing the exchange of seawater around the polyp, thereby providing a simple and inexpensive polyp killing method. be able to.

  The present invention is a method for easily and inexpensively killing a jellyfish polyp at its actual place of establishment. Specifically, the place of polyp buildup is covered with a bubble buffer sheet to prevent exchange of seawater around the polyp. It is characterized by killing a polyp.

  The principle of killing polyps in the method of the present invention can be considered as follows. Since polyps cannot move from their place of origin by themselves, they obtain food (mainly plactone) and oxygen from the surrounding seawater. Since the seawater around the polyp is always changed under normal conditions, the seam is continuously supplied with fresh seawater containing food and oxygen. However, if the exchange of seawater around the polyp is prevented here, the polyp will no longer be supplied with fresh seawater, so after a certain amount of time, the polyp will consume food and oxygen in the surrounding seawater and be weakened. However, it will eventually be killed.

  The place where the polyp killing method of the present invention is carried out is the place where the polyp is settled, specifically, the seawater contact area on the lower surface of the structure existing on the sea surface such as the lower surface of the floating pier or the lower surface of the overhang of the breakwater It is. Since these places are located several meters below the sea level, almost no waves are generated, and it has been found that jellyfish polyps tend to settle. Further, since these places hardly generate waves, it has been found that there is almost no risk that the installed bubble buffer sheet is displaced or peeled off by the waves. Therefore, when the polyp killing method of the present invention is carried out in these places, the polyp can be killed effectively.

  In the polyp killing method of the present invention, a bubble cushioning sheet is adopted as a means for covering the polyp place and preventing the exchange of seawater around the polyp. Since the bubble cushioning sheet contains a large amount of bubbles inside, the buoyancy is extremely large as compared with other bubble-containing plastic materials such as expanded polystyrene. Moreover, the bubble buffer sheet is excellent in flexibility as compared with the polystyrene foam. Therefore, when a foam cushioning sheet is applied from below to the polyp formation area such as the bottom of the floating pier or the bottom of the overhang of the breakwater, the sheet will stick to the polyp formation area due to its buoyancy and flexibility. The exchange of seawater around the polyp can be reliably prevented.

  As the foam cushioning sheet used in the method of the present invention, any of those commercially available as a packing material can be adopted, and in particular, a biodegradable plastic foam used for heat retention in the agricultural field. A buffer sheet is preferred. If a bubble buffer sheet made of biodegradable plastic is used, the sheet will be naturally decomposed in seawater after a certain amount of time, eliminating the need to collect the bubble buffer sheet after the polyp dies. This is advantageous from the viewpoint of protection.

  The bubble cushioning sheet can be installed by covering the seawater contact area on the lower surface of the structure existing on the sea surface where the polyp to be killed is deposited with the bubble cushioning sheet from below. Since the installed bubble cushioning sheet tends to float by its buoyancy, it is fixed to the seawater contact area on the lower surface of the structure existing on the sea surface, where the flexibility of the sheet causes the surface shape of the seawater contact area to follow the surface shape of the seawater contact area. The seawater contact area will be covered closely. At this time, it is desirable to extrude air from the center of the bubble buffer sheet toward the periphery so that air does not remain as much as possible between the bubble buffer sheet and the seawater contact region. The coated bubble buffer sheet is tightly fixed to the seawater contact area without being fixed with an adhesive or the like because of its large buoyancy and flexibility and gentleness of the waves in the seawater contact area. This reliably prevents the exchange of seawater around the polyp and kills the polyp.

  In the method for killing polyps according to the present invention, it is desirable to cover the polyp deposition site with the bubble cushioning sheet for a time sufficient for the polyps to die without being able to ingest food or oxygen, specifically at least one month. It is preferable to maintain the intermediate coating state. In addition, when the jellyfish is a moon jellyfish, it is preferable to select the time from the end of autumn to the beginning of winter as the implementation time of the method of the present invention. The jellyfish polyp is known to start strobulation when the water temperature falls to 15 ° C. or less, and to begin liberating effira larvae. In the case of moon jellyfish, it is known that new planula larvae adhere to and reproduce from summer to autumn, and liberate effira larvae when seawater temperature decreases in winter. Therefore, by performing the method of the present invention at the time immediately before the end of autumn and the beginning of winter, when the new planula adhesion of the moon jellyfish is completed and the seawater temperature falls below 15 ° C., the generation of moon jellyfish is ensured. Can be prevented.

  According to the method of the present invention, the polyps can be easily and inexpensively killed in the habitat of the jellyfish polyps that attack the seawater utilization plant such as a thermal power plant. Can be efficiently prevented.

  Hereinafter, the effectiveness of the method of the present invention will be described more specifically by showing examples, but the present invention is not limited thereto.

Test place A place where moon jellyfish polyps were densely settled in the seawater contact area under the overhang of a breakwater at a fishing port on the coast of the Sea of Japan was selected, and this place was taken as the test place. The condition of the polyp deposition area is that barnacles adhere to the underside of the overhang of the breakwater without any gaps, and mussels and oysters adhere to it in some places. It was in a live state (see FIG. 1).

Test Method Two sections having substantially the same polyp growth condition with the naked eye were selected from the test place. Of these, a commercially available bubble buffer sheet having a size of 1 m × 1 m was covered from below with a diving, and was closely adhered to one section (treatment section) so that no seawater exchange occurred in that section. The covering state is shown in FIG. As shown in Fig. 1, the polyp deposition area at this test site has a lot of shells such as mussels and oysters on barnacles. Covered the polypeneed region in close contact with the uneven surface due to its excellent buoyancy and flexibility. No bubble buffer sheet was installed in the remaining one section (untreated section).

  The test was conducted over a month from late November to late December. One month after the start of the test, the bubble buffer sheet in the treated section was removed again by diving, and the polyp survival state in the treated and untreated sections was observed by photography. The result is shown in FIG. As can be seen from FIG. 3, in the untreated section, the polyp is densely deposited as before the start of the test, whereas in the treated section covered with the bubble buffer sheet for one month, the polyp is dead and is a dead body of the polyp. Only brown mud slime remained on the surface of barnacles and shellfish. In addition, 10 mussels or oysters of approximately the same size were collected from each compartment, and the number of polyps adhering to the surface of these shellfish was counted by microscopic observation. Whereas 469 polyps (standard deviation ± 152) were attached, the average number of attached polyps per shellfish was 0 (standard deviation was also 0) in the treatment section covered with a foam cushion sheet for 1 month. It was.

  From the above results, it is clear that the polyp can be easily and reliably killed by covering the polyp place with a bubble buffer sheet to prevent the exchange of seawater.

  According to the present invention, a jellyfish polyp can be killed easily and inexpensively at an actual place of establishment such as the back of a floating jetty or the back of a breakwater overhang, thereby effectively preventing the occurrence of jellyfish. Therefore, the present invention can be effectively used to prevent a jellyfish from invading a seawater utilization plant such as a thermal power plant.

It is a photograph which shows the polyp formation state of the test place before a test start. It is a photograph which shows the covering state of the processing division by a bubble buffer sheet. It is a photograph which shows the polyp survival state of the processing division at the time of completion | finish of a test, and an untreated division. It is a schematic diagram which shows the life history of a moon jellyfish.

Claims (4)

  A method for killing a polyp, characterized in that the seawater contact area on the lower surface of the structure existing on the sea surface where the jellyfish polyp is deposited is covered with a bubble cushioning sheet to prevent exchange of seawater around the polyp.   The method according to claim 1, wherein the coating with the foam cushioning sheet is performed for at least one month.   The method according to claim 1 or 2, wherein the foam cushioning sheet is formed from a biodegradable plastic.   The method according to any one of claims 1 to 3, wherein the seawater contact region where the polyp is deposited is a lower surface of a floating jetty or a lower surface of an overhang of a breakwater.