JP4884283B2 - Bivalve breeding method and substrate for improving bottom sediment - Google Patents

Bivalve breeding method and substrate for improving bottom sediment Download PDF

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JP4884283B2
JP4884283B2 JP2007107105A JP2007107105A JP4884283B2 JP 4884283 B2 JP4884283 B2 JP 4884283B2 JP 2007107105 A JP2007107105 A JP 2007107105A JP 2007107105 A JP2007107105 A JP 2007107105A JP 4884283 B2 JP4884283 B2 JP 4884283B2
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specific gravity
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JP2008263791A (en
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健二 森田
秀樹 山岸
良男 田中
進 木村
千晶 小柳
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株式会社東京久栄
株式会社パジコ
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Description

本発明は、二枚貝類の増殖方法および底質改善基材に関するものである。   The present invention relates to a bivalve growth method and a bottom sediment improving base material.

干潟などの浅場には多数の二枚貝類の生息が確認されており、例えば東京湾の盤州干潟にはアサリやホトトギスガイが生息する。上記アサリは体外受精によって繁殖し、孵化した個体は幼生（浮遊幼生）として水中を漂った後、着底して稚貝から成貝へと成長する。アサリの幼生あるいは稚貝は、着底に際して小石の脇などの比較的安定した場所を好むことが経験的に知られており、タンパク質からなる足糸を小石等に付着させ、この後、小石等の脇の砂に潜る行動をとることが観察されている。このように砂に潜る行為は潜砂行動と呼ばれる。一方、上記ホトトギスガイは同じ二枚貝類であるが、足糸を小石等に付着させて潜砂行動をとることなくそのまま着底を完了する。   Many shallow clams are found in shallow areas such as tidal flats. For example, clams and white mussels live in the Banshu tidal flats in Tokyo Bay. The clams breed by in vitro fertilization, and the hatched individuals drift in the water as larvae (floating larvae), then settle down and grow from juveniles to adult clams. It has been empirically known that clams larvae or juveniles prefer relatively stable places such as the side of pebbles when they settle down, and attach a protein foot thread to pebbles, etc. It has been observed to take action in the sand beside the sea. This act of diving in the sand is called diving action. On the other hand, the above mussel is the same bivalve, but the bottoming is completed as it is without attaching a foot thread to a pebble or the like and taking a dive action.

以上のようなアサリ等の二枚貝類は、近年我が国において大幅な減少傾向にあり、資源復活としてその増殖が強く求められている。特にこれらの幼生、稚貝は、上述した小石等の安定した基質に着底できないという理由によって生存率が極めて低くなることが確認されており、これを高めることが資源復活のみならず生物多様性や水底質改善の有効な対策になる。   The bivalves such as clams as described above have been decreasing in recent years in Japan, and their proliferation is strongly demanded as a resource recovery. In particular, it has been confirmed that these larvae and juvenile shellfish have a very low survival rate because they cannot settle on the above-mentioned stable substrates such as pebbles. It is an effective measure for improving water quality.

この点、特許文献１には、アサリの幼生期から成貝期までのライフサイクルを考慮し、適切な粗砂分の含有率を備えた干潟覆砂材料を用いる干潟造成方法が提案されている。
特開２００６-２７４６９０ In this regard, Patent Document 1 proposes a tidal flat creation method using a tidal flat covering material with an appropriate content of coarse sand in consideration of the life cycle from the larval stage to the adult clam stage of clams. .
JP 2006-274690

しかしながら、上記従来例は、外部環境をあまり考慮していないために、以下の欠点がある。すなわち、自然の水生環境下においては、波の流れにより定常的な所定の水勢が生じる場合のほかに、時折、大型低気圧の襲来などによって極めて強い水勢を生じる場合がある。この点、上記従来例のように粗砂、すなわち単に細粒分との嵩の違いに基づく重量差によって定常時における水中での安定性を確保する場合、極めて強い水勢を受けて粗砂が細粒分とともに流されてしまうと、波等のうねりによってある種の分級がなされて粗砂が水底表層部に露出しにくくなり、以後アサリ等の二枚貝類の幼生、稚貝の着底が良好に促進されなくなってしまう。   However, the above conventional example has the following drawbacks because it does not take into account the external environment. In other words, in a natural aquatic environment, in addition to the case where a steady predetermined water force is generated due to the flow of waves, an extremely strong water force is sometimes generated due to the attack of a large low pressure. In this regard, as in the above-described conventional example, when ensuring stability in water in a steady state due to the difference in weight based on the difference in bulk from the coarse sand, that is, the fine particles, the coarse sand is subjected to extremely strong water and is fine. If it is washed away along with the grain, some sort of classification will occur due to swells such as waves, making it difficult for the coarse sand to be exposed on the surface of the bottom of the water. It will not be promoted.

本発明は、以上の欠点を解消すべくなされたものであって、アサリ等の二枚貝類の幼生、稚貝の着底をより長期に渡って安定して促進することができる二枚貝類の増殖方法、および底質改善基材の提供を目的とする。 The present invention has been made to eliminate the above-mentioned drawbacks, and is a bivalve propagation method that can stably promote the settlement of clams such as clams and the bottom of clams over a long period of time. The present invention aims to provide a substrate for improving bottom sediments.

本発明によれば上記目的は、
ほぼ粒状の底質改善基材２の多数をアサリ等の二枚貝類の生息域における砂１を含む水底３に散布してアサリ等の二枚貝類の幼生、稚貝５の着底を促してなり、
前記底質改善基材２は、通常の波を受けてあまり移動しないとともに、強い波によってシートフローが生じた際に底質が液状化してなる層状の漂砂に埋もれることなく水底表層部４をほぼ維持する１．１から１．７までの範囲内の嵩比重、および砂１よりも嵩の張る大きさに、砕いた貝殻を比重調整材料として粘土に加えて成形、焼成することにより形成される二枚貝類の増殖方法を提供することにより達成される。 According to the present invention, the object is
Almost larvae bivalves such as A Sari by dispersing the water bottom 3 containing sand 1 a number of bottom sediment improvement substrate 2 of the particulate in the habitat of bivalves such as clams, and prompting the wearing bottom of spats 5 And
The bottom sediment improvement base material 2 does not move so much by receiving normal waves, and the bottom surface layer portion 4 is almost buried without being buried in the layered sand that is liquefied when the sheet flow is generated by strong waves. It is formed by molding and firing crushed shells in addition to clay as a specific gravity adjusting material to a bulk specific gravity in the range of 1.1 to 1.7 to be maintained, and to a bulkier size than sand 1. This is accomplished by providing a method for breeding bivalves.

本発明によれば、水底３に散布される底質改善基材２は、底質の砂１よりも嵩比重を小さくされ、したがって水底表層部４の砂１よりも沈降しにくく、極めて強い水勢を受けて底質が液状化したときにも、容易に砂１に埋もれてしまうことはない。また底質改善基材２は、砂１よりも嵩の張るほぼ粒状に形成され、これにより上述した小さい嵩比重に起因する個体としての小さい質量が補われ、少なくとも一部のみを水中に露出させて砂１に多少埋もれた状態になれば、定常的な水勢を受けても水中に完全に露出する砂１に比べて流されにくい。   According to the present invention, the bottom material improving base material 2 sprayed on the water bottom 3 is made to have a lower bulk specific gravity than the sand 1 of the bottom material, and therefore is less likely to settle than the sand 1 of the surface layer 4 of the bottom, and has an extremely strong water power. Even when the bottom is liquefied, it is not easily buried in the sand 1. Moreover, the bottom material improvement base material 2 is formed in the substantially granular form bulky rather than the sand 1, and this compensates the small mass as a solid resulting from the small bulk specific gravity mentioned above, and exposes only at least one part in water. If the sand is slightly buried in the sand 1, it is less likely to be washed away than the sand 1 that is completely exposed to the water even when subjected to a steady water force.

一般に、干潟などにおける底質の移動、漂砂は、通常の波を受けて砂などが転動等しながら粒子単位で運ばれるいわゆる掃流移動と、強い波を受けて底質自体が液状化して層状に移動するいわゆるシートフローに大別することができる。したがって本発明によれば、底質改善基材２を容易に掃流移動しないようにすることができ、シートフローにおいては層状の塊として捉えることが可能な砂などに埋もれにくくすることができ、これにより、干潟などの水底表層部４にアサリ等の二枚貝類の幼生、稚貝５の着底に適した安定した基質を長期に渡って確保することができる。   In general, sediment movement and drifting sand in tidal flats, etc., is the so-called scavenging movement in which sand is moved by particles while receiving normal waves, and the sediment itself is liquefied by receiving strong waves. It can be roughly divided into so-called sheet flows that move in layers. Therefore, according to the present invention, it is possible to prevent the bottom quality improving base material 2 from being easily moved by scavenging, and in the sheet flow, it is possible to make it difficult to be buried in sand or the like that can be captured as a layered lump. As a result, a stable substrate suitable for the settlement of bivalve larvae such as clams and juveniles 5 can be secured over a long period of time on the surface layer 4 of the bottom of the tidal flat.

なお、底質における砂の動きやすさを示す指標であるいわゆるシールズ数の計算方法によれば、砂の動きやすさは、比重と、粒径、すなわち嵩とのそれぞれに反比例する。これから演繹的に推論すれば、底質改善基材２について、シートフローにおいて砂に埋もれにくいための嵩比重を備えていても、砂よりも嵩張らせることによって、掃流移動しにくくすることができ、このように比重と嵩のバランスをとることによって、長期的に水底表層部４に維持させることができると考えることができる。   In addition, according to the so-called Shields number calculation method, which is an index indicating the mobility of sand in the sediment, the mobility of sand is inversely proportional to the specific gravity and the particle size, that is, the bulk. Inferring a priori from this, even if the bottom quality improving base material 2 has a bulk specific gravity that is difficult to be buried in the sand in the sheet flow, it can be made difficult to move by sweeping by making it bulkier than the sand. Thus, it can be considered that the bottom layer 4 can be maintained for a long time by balancing the specific gravity and the bulk.

底質改善基材２を水底３に散布すれば、定常的な波によって底質改善基材２の水底３側の部位が自然と水底表層部４の砂１等に埋もれた底質が形成され、これにより上述したように底質改善基材２が流されにくくなることから、本発明によれば、水底３で安定した基質として機能する底質改善基材２のみを散布するだけで、アサリ等の二枚貝類の幼生、稚貝５の着底をより長期に渡って安定して促進させることができる。また、二枚貝類の幼生等５が潜砂行動をとる場合における砂１は、そのまま干潟等の現地におけるものになるために、外部から持ち込むことによる生物親和性や二枚貝類の幼生等５への違和感の心配はない。さらに、定常的な所定の水流によって運ばれる極めて長期間に渡る砂１の積み重ねや生物の摂餌等に伴う撹乱によって底質改善基材２が仮に埋没してしまったとしても、耕耘をすれば足り、底質改善基材２の嵩比重の小ささによって耕耘による機能回復を極めて良好にすることができる。   If the bottom sediment improving base material 2 is sprayed on the water bottom 3, a bottom sediment in which a portion of the bottom sediment improving base material 2 on the water bottom 3 side is buried in the sand 1 etc. of the water bottom surface layer 4 is formed by a steady wave. As described above, the bottom sediment improving base material 2 is less likely to be washed away, and according to the present invention, only the bottom sediment improving base material 2 that functions as a stable substrate at the water bottom 3 is sprayed, and the clam It is possible to stably promote the settlement of the bivalve larvae and the bottom of the larvae 5 for a longer period of time. In addition, sand 1 when bivalve larvae 5 take a submersible action becomes the local one such as tidal flats, so biocompatibility by bringing in from the outside, bivalve larvae 5 etc. There is no worry. Furthermore, even if the sediment-improving base material 2 is buried due to the disturbance caused by the accumulation of sand 1 or the feeding of organisms over a very long period of time carried by a steady predetermined water flow, It is sufficient, and the functional recovery by tillage can be made very good by the small bulk specific gravity of the bottom material improving base material 2.

上記底質改善基材２は、上述した小石に相当するようなほぼ粒状に形成され、水流が過剰に衝突しないように配慮される。より具体的な形状は適宜決定することが可能であるが、例えば円柱形状などの転がりやすい形状にすれば、ホトトギスガイのように着底後に移動しない種別の幼生等の増殖を適宜抑えると同時に、アサリのように着底後に移動できる種別の幼生等５の増殖を伸ばすことも可能になる。   The bottom material improving base material 2 is formed in a substantially granular shape corresponding to the above-described pebbles, and consideration is given so that the water flow does not collide excessively. More specific shape can be determined as appropriate, for example, if it is easy to roll, such as a cylindrical shape, while appropriately suppressing the growth of larvae of the type that does not move after landing, It is also possible to increase the growth of 5 types of larvae that can move after landing, such as clams.

底質改善基材２の多数の水底３への散布は、それぞれの底質改善基材２同士が水底３で積み重ならないように行うことも可能であるが、積み重ねたときには、底質改善基材２、２間に狭い隙間が生じ、該隙間への砂１等の充填によって、より安定性の高い二枚貝類の幼生等５の潜砂領域を形成することが可能である。なお、上記隙間への砂１等の充填や、上述した底質改善基材２の水底３側の部位の砂１等による埋設は、上述したように砂１等が自然の水流によって流されることを利用して実現することが可能であるが、このように密集して散布した場合など、条件に応じて人工的に行うことも可能である。また、以上の点などを考慮した場合には、底質改善基材２の具体的な大きさ、嵩については、仮に粒径で特定するならば２ｍｍから５０ｍｍの範囲内であることが望ましいと考えられる。   It is possible to spread the bottom quality improving base material 2 on a large number of water bottoms 3 so that the bottom quality improving base materials 2 are not stacked on the bottom 3. A narrow gap is formed between the materials 2 and 2, and by filling the gap with sand 1 or the like, it is possible to form a more stable submarine area of bivalve larvae 5 or the like. In addition, as described above, the filling of the gap 1 with the sand 1 or the like, and the embedding of the portion on the water bottom 3 side of the bottom sediment improvement base material 2 with the sand 1 or the like, the sand 1 or the like is caused to flow by a natural water flow as described above. However, it can also be artificially performed according to conditions, such as when densely sprayed. Moreover, when the above points are taken into consideration, it is desirable that the specific size and bulk of the bottom sediment improving base material 2 should be in the range of 2 mm to 50 mm if specified by the particle size. Conceivable.

また、上述した底質改善基材２の嵩比重を定量的に表現するならば、少なくとも砂１の一般的な真比重である２．６前後よりも低いものとして特定することが可能で、これによれば砂１よりも沈降しにくいという効果を期待できると言える。この砂１の真比重は砂１よりも小さい水底の土粒子、すなわちシルトや粘土にも一般に共通し、したがって極めて強い水勢を受けた後の底質改善基材２のこれらによる埋没についても同時に良好に抑制することができる。また、発明者の知見、実験によれば、シートフローによって底質が液状化した層状になった場合、かかる層としての嵩比重を想定、比較考慮すれば、上記底質改善基材２の嵩比重は１．１から１．７までの範囲内であることが望ましい。このような数値範囲の比重を有する自然素材はアサリ等の二枚貝類の生息域における底質には見付けることができず、したがってこれによればアサリ等の二枚貝類の増殖に適した新たな底質を創出することができる。   Moreover, if the bulk specific gravity of the above-mentioned bottom sediment improving base material 2 is expressed quantitatively, it can be specified as being lower than at least about 2.6, which is a general true specific gravity of sand 1, According to the above, it can be said that the effect of being less likely to settle than sand 1 can be expected. The true specific gravity of the sand 1 is generally common to soil particles on the bottom of the water smaller than the sand 1, ie, silt and clay, and therefore the bottom sediment improvement base material 2 after being subjected to extremely strong water is also good at the same time. Can be suppressed. Further, according to the inventor's knowledge and experiment, when the bottom sediment is liquefied by the sheet flow, the bulk of the bottom sediment-improving substrate 2 is assumed by considering and comparing the bulk specific gravity as the layer. The specific gravity is preferably in the range of 1.1 to 1.7. Natural materials with specific gravity in such a numerical range cannot be found in the bottom sediments of clams such as clams, so new sediment suitable for the growth of clams such as clams Can be created.

さらに、上記底質改善基材２は、長期の物理的安定性を考慮すればセラミックスにより形成することが望ましい。セラミックスの代表的な主原料としての陶土は真比重が高く、仮に気泡などの空間を内部に豊富に備えた多孔質体からなるセラミックスであっても上述した嵩比重を実現するには真比重の低い添加材料を混合する必要がある。この点、貝殻は一般に真比重が水にほぼ近似する程度と低く、かかる比重調整に適する上に、これを添加材料として用いることにより、貝との生物親和性が高い基質を容易に構成することができる。   Furthermore, it is desirable to form the bottom material improving base material 2 from ceramics in consideration of long-term physical stability. Porcelain clay as a typical main raw material of ceramics has a high true specific gravity, and even if it is a ceramic made of a porous body with abundant spaces such as bubbles inside, the true specific gravity is necessary to realize the above-mentioned bulk specific gravity. Low additive materials need to be mixed. In this regard, shells generally have a low true specific gravity that is almost similar to that of water. In addition to being suitable for adjusting the specific gravity, using this as an additive material makes it easy to construct a substrate with high biocompatibility with shellfish. Can do.

また、貝殻の主成分である炭酸カルシウム（ＣａＣＯ３）は、焼成によって、より具体的には約９００度以上の焼成によって、酸化カルシウム（ＣａＯ）に変化し、さらにこの酸化カルシウムは、水和反応によって水酸化カルシウム（Ｃａ（ＯＨ）２）に変化する。水和反応時のｐＨ上昇は水酸化カルシウム同士、すなわち底質改善基材２、２同士の適度の癒着をもたらし、したがって嵩比重の小さい底質改善基材２を流失しにくくすることができる。さらに、底質改善基材２の多数が相互に癒着することを実現するために、水底３に適宜積み重なるように底質改善基材２の多数を水上から散布すれば、水底３の地形に合わせて底質改善基材２を配置することができる。この底質改善基材２は量産性を考慮すれば定形であることが望ましく、この場合、多数を散布したときに互い間隙を持って積み重なる形状、例えば曲面を備えるものであることが望ましい。 In addition, calcium carbonate (CaCO 3 ), which is the main component of the shell, is changed to calcium oxide (CaO) by firing, more specifically by firing at about 900 ° C. or more, and this calcium oxide further undergoes a hydration reaction. Changes to calcium hydroxide (Ca (OH) 2 ). The increase in pH during the hydration reaction brings about moderate adhesion between calcium hydroxides, that is, the bottom-improving base materials 2 and 2, so that the bottom-quality improving base material 2 having a small bulk specific gravity can be prevented from being washed away. Furthermore, in order to realize that many of the bottom sediment improvement base materials 2 adhere to each other, if many of the bottom sediment improvement base materials 2 are sprayed from above the water so that they are appropriately stacked on the bottom of the water 3, the bottom sediment improvement base material 2 is adjusted to the topography of the bottom of the water bottom 3 The bottom material improving base material 2 can be disposed. In consideration of mass productivity, the bottom material improving base material 2 is desirably in a fixed shape, and in this case, it is desirable to have a shape such as a curved surface that is stacked with a gap between each other when a large number are dispersed.

加えて、水和反応に伴う発熱による底質改善基材２の破損や水生生物への悪影響を防ぐため、底質改善基材２における酸化カルシウムの含有量は適度に抑えておくことが望ましい。焼成によって製作する場合における底質改善基材２の嵩比重の軽減には、上述したように貝殻などの真比重の低い材料を添加する以外に、気泡を豊富にしたり、吸水性を高めることが有効で、焼き締まりを抑える低温焼成が効果的である。通常の陶磁器などにおける１２００度以上の焼成温度よりも低い温度で焼成するときには、より耐熱性能が高く、粒径の小さな材料をさらに添加しておけば、効率的に嵩を増やして嵩比重を軽減することが期待できる。   In addition, in order to prevent damage to the bottom sediment-improving base material 2 and adverse effects on aquatic organisms due to heat generated by the hydration reaction, it is desirable that the content of calcium oxide in the bottom sediment-improved base material 2 is appropriately suppressed. In order to reduce the bulk specific gravity of the bottom sediment-improving base material 2 when it is manufactured by firing, in addition to adding a material having a low true specific gravity such as a shell as described above, it is possible to enrich the bubbles or increase the water absorption. It is effective and low-temperature firing is effective to suppress firing. When firing at a temperature lower than 1200 ° C or higher in ordinary ceramics, etc., adding a material with higher heat resistance and smaller particle size will effectively increase the bulk and reduce the bulk specific gravity. Can be expected to do.

また、水中において砂１よりも沈降しにくくすることを考えれば、底質改善基材２は、実質的には、その水中重量を体積で割った水中における嵩比重を基準に考えたときに、砂１よりも小さいものであることが有効である。この場合において底質改善基材２をセラミックスで形成したときには、独立気泡（閉気孔）を設けて水中重量を大きく軽減したり、連続気泡（開気孔）を増やして底質改善基材２の吸水率を高めたりすることが望ましい。高い吸水率は、干潮時に干出する水底３に底質改善基材２が散布された時には、打ち上げ波に対する安定度を高めるとともに、周辺土壌の保水率を高めることにもつながり、例えば水温の過度な上昇を防ぐ、間隙水による呼吸可能時間が長くなるなどアサリをはじめとする干潟生物の生息環境を安定化し、結果として資源の減耗を防ぐことになると考えられる。   Further, considering that it is more difficult to settle than sand 1 in the water, the bottom sediment improving base material 2 is substantially based on the bulk specific gravity in water obtained by dividing the weight of the water by volume. It is effective to be smaller than the sand 1. In this case, when the bottom material improving base material 2 is formed of ceramics, closed cells (closed pores) are provided to greatly reduce the weight in water, or the open cell (open pores) are increased to absorb water from the bottom material improving base material 2. It is desirable to increase the rate. A high water absorption rate increases the stability to the launch wave and increases the water retention rate of the surrounding soil when the bottom sediment improvement base material 2 is sprayed on the bottom 3 that is dried out at low tide. This will stabilize the habitat of tidal flats such as clams and prevent resource depletion.

以上の説明から明らかなように、本発明によれば、アサリ等の二枚貝類の幼生、稚貝の着底をより長期に渡って安定して促進することができる二枚貝類の増殖方法、および底質改善基材を提供することができ、アサリ等の二枚貝類の資源復活、再生を良好に図ることができる。 As is clear from the above description, according to the present invention, a bivalve breeding method that can stably promote the settlement of bivalve larvae such as clams, the settlement of juveniles over a longer period, and the bottom A quality-improving base material can be provided, and resource recovery and regeneration of clams such as clams can be favorably achieved.

図１および図２に本発明の実施の形態を示す。図１は底質改善基材２の水底表層部４での状態を示すもので、この実施の形態において底質改善基材２は、転がりやすく、積み重ねたときに隙間を生じる円柱形状に形成される。図２（ｂ）に示すように、底質改善基材２は、直径Ｄ、長さＬがともに約１０ｍｍからなるほぼ粒状で、粘土としての陶土に比重調整材料を添加して成形、焼成することによって、１．６程度の嵩比重（空気中）を有して砂１よりも水中嵩比重が小さくなるように調整される。   1 and 2 show an embodiment of the present invention. FIG. 1 shows a state of the bottom quality improving base material 2 at the water bottom surface portion 4. In this embodiment, the bottom quality improving base material 2 is easy to roll and is formed in a cylindrical shape that creates a gap when stacked. The As shown in FIG. 2 (b), the bottom quality improving base material 2 is substantially granular having both a diameter D and a length L of about 10 mm, and is molded and fired by adding a specific gravity adjusting material to clay as clay. Therefore, the underwater bulk specific gravity is adjusted to be smaller than that of the sand 1 having a bulk specific gravity (in air) of about 1.6.

上述した比重調整材料として貝殻を用いるこの実施の形態において、成形原料は、陶土と貝殻を約８０％と約２０％の割合で混合して生産される。この混合原料は、ボールミルに調合された陶土としての木節粘土と貝殻をともに投入して粉砕、混合することにより、木節粘土がおよそ３０ミクロン以下、貝殻が陶土よりもやや粗い程度、およそ３００ミクロン以下のパウダー状で混和した成形原料としての粉体が生産される。   In this embodiment using a shell as the specific gravity adjusting material described above, the forming raw material is produced by mixing porcelain and shell at a ratio of about 80% and about 20%. This mixed raw material is made by adding together crushed clay and shells as porcelain clay prepared in a ball mill, pulverizing and mixing them, so that the crushed clay is about 30 microns or less and the shells are slightly coarser than porcelain, about 300 A powder as a molding raw material mixed in a powder form of micron or less is produced.

底質改善基材２の生産は、以上のようにして得られた粉体に水を加えて泥状にした後、フィルタープレスにより濾過、脱水したケーキ状にし、この後ニーダーで混練し、押し出し成形機に充填してなされる。押し出し成形は成形原料を直径約１０ｍｍの長尺の円柱状に成形し、成形後の原料は、適宜乾燥した後、ロータリーキルンや電気炉等に投入されて焼成される。焼成温度は１０８０度から１１００度で、これにより適宜の強度、吸水率が確保される。なお、成形は乾式の加圧成形により行うことも可能で、この場合には上述した泥状の粉体をスプレードライヤで適宜乾燥すれば足りる。   For the production of the bottom-improved base material 2, water is added to the powder obtained as described above to make a mud, which is then filtered and dehydrated by a filter press, then kneaded by a kneader and extruded. It is done by filling the molding machine. In extrusion molding, a forming raw material is formed into a long cylindrical shape having a diameter of about 10 mm, and the formed raw material is appropriately dried and then put into a rotary kiln, an electric furnace or the like and fired. The firing temperature is from 1080 degrees to 1100 degrees, thereby ensuring appropriate strength and water absorption. The molding can also be performed by dry pressure molding. In this case, it is sufficient to appropriately dry the above-mentioned mud powder with a spray dryer.

この後、長尺の円柱状からなる焼成体を長さが１０ｍｍ程度になるように適宜切断することにより底質改善基材２は完成する。以上のように嵩比重の小さい貝殻を適宜の調合具合で陶土に添加し、低温焼成することによって、底質改善基材２は１０％の吸水率を備えた表面が粗面からなる多孔質体として形成され、嵩比重が砂１よりも低く抑えられる。また、焼成によって貝殻に含まれる炭酸カルシウムが酸化カルシウムになり、底質改善基材２は貝殻の調合量、粉砕粒度、貝殻に含有される炭酸カルシウムの量に応じた適度の水和反応性を備える。   Thereafter, the bottom quality improving base material 2 is completed by appropriately cutting the fired body having a long cylindrical shape so that the length is about 10 mm. As described above, by adding a shell with a small bulk specific gravity to porcelain clay in an appropriate blending condition and firing at low temperature, the bottom material improving base material 2 is a porous body having a rough surface with a water absorption of 10%. The bulk specific gravity is suppressed to be lower than that of the sand 1. In addition, the calcium carbonate contained in the shell is converted to calcium oxide by firing, and the bottom material improving base material 2 has an appropriate hydration reactivity according to the amount of shell shell prepared, the pulverized particle size, and the amount of calcium carbonate contained in the shell. Prepare.

なお、以上においては陶土と貝殻のみを原料とする場合を示したが、陶土を他の原料で代替したり、あるいは他の材料をさらに添加して水和反応性や比重、強度、吸水率などの能力を調整することも可能である。例えば、蛙目粘土、ドロマイト、長石、陶石、あるいは、比重調整材料としての珪砂、磁器セルベン、軽量骨材、さらには適宜の焼結体を代替材料、添加材料にすることができる。また、このような底質改善基材２の能力は、底質改善基材２が散布される水域の状況に合わせて適宜決定され、例えば原料の調合分量、粉砕の程度、焼成温度、焼成時間、さらには発泡剤の添加によっても適宜調整することが可能である。加えて、上述した焼成温度では融解あるいはあまり軟化しない材料を添加し、単に嵩張らせたり、あるいは適宜に焼結させて空隙率をより高めることも可能である。   In the above, the case where only porcelain clay and shells are used as raw materials has been shown, but the hydration reactivity, specific gravity, strength, water absorption rate, etc. can be changed by replacing porcelain with other raw materials or by adding other materials. It is also possible to adjust the ability. For example, glazed clay, dolomite, feldspar, porcelain stone, silica sand as a specific gravity adjusting material, porcelain selben, lightweight aggregate, and appropriate sintered body can be used as an alternative material or additive material. Moreover, the capability of such a bottom improvement base material 2 is determined suitably according to the condition of the water area where the bottom improvement base material 2 is spread, for example, the amount of raw material, the degree of pulverization, the firing temperature, and the firing time. Further, it can be appropriately adjusted by adding a foaming agent. In addition, it is possible to add a material that does not melt or soften so much at the above-described firing temperature, and simply increase the porosity by sintering the material appropriately or by sintering it appropriately.

また、以上においては長尺の円柱状からなる焼成体を長さ１０ｍｍ毎に切断して多数の底質改善基材２、２・・を得る場合を示したが、成形時に予め１０ｍｍ長さの円柱形状に成形した後、焼成して製造することも可能である。   Moreover, in the above, the case where a fired body made of a long columnar shape is cut every 10 mm to obtain a large number of bottom material improving base materials 2, 2. It is also possible to manufacture by firing after forming into a cylindrical shape.

以上のようにして得られた底質改善基材２を水底３に散布して二枚貝類の増殖に適するように底質を改善するこの発明において、この実施の形態においては、特にアサリの増殖に適した底質の改善がなされる。底質の改善は、アサリの生息域である例えば干潟の潮間帯付近に底質改善基材２の多数を相互に適度に積み重なるように水上から散布してなされる。   In the present invention in which the bottom sediment improving base material 2 obtained as described above is sprayed on the water bottom 3 to improve the bottom sediment so as to be suitable for the growth of bivalves, in this embodiment, particularly for the propagation of clams. A suitable bottom quality improvement is made. Improvement of the bottom sediment is made by spraying a large number of bottom sediment improvement base materials 2 from above the water so as to be appropriately stacked on each other, for example, in the vicinity of the intertidal zone of a tidal flat which is a habitat for clams.

嵩比重が砂１より小さい底質改善基材２は、水上からの散布によってゆっくりと沈降し、例えば、干潟水底３に形成される砂漣の形状に合わせて多数が適宜に積み重なる。図２（ａ）に示すように、積み重なりが自然と不均一になるその円柱形状と相まって、底質改善基材２の多数は不均一に積み重なり、平面視や側面視で多数の間隙を形成する。また、水中に投入され、積み重なることにより接触する底質改善基材２、２同士は、それぞれが含有する酸化カルシウムの水和反応によって癒着し、単体であるときに比べて水流に対する安定性が高められる。   Sediment-improving base material 2 having a bulk specific gravity smaller than sand 1 slowly settles by spraying from the surface of the water, and, for example, many pile up appropriately according to the shape of the sand basin formed on tidal flat bottom 3. As shown in FIG. 2A, coupled with the cylindrical shape in which stacking is naturally non-uniform, a large number of bottom sediment improvement base materials 2 are stacked non-uniformly, forming a large number of gaps in plan view and side view. . Moreover, the bottom sediment improvement base materials 2 and 2 which are thrown into water and are contacted by being piled up are adhered by the hydration reaction of the calcium oxide contained therein, and the stability to the water flow is improved as compared with a single substance. It is done.

この後、干潟の波によって、水底３に沈降した底質改善基材２の周囲や上述した間隙には、次第に干潟の底質の砂泥が適宜流れ着き、これにより底質改善基材２がその嵩との相乗効果で水底３に適宜露出する安定した基質を構成し、その周囲の間隙によりアサリの幼生等５の着底に適した安定した潜砂領域を提供する。また、上記間隙は底質の空隙率を高めて適宜の通水を導き、酸素や栄養塩供給を活発にしてアサリの幼生等５の餌となるプランクトン等の増殖をも確保する。   Thereafter, sand mud in the bottom of the tidal flat gradually flows around the bottom sediment improving base material 2 that has settled on the water bottom 3 due to the waves of the tidal flat and the above-described gap. A stable substrate that is appropriately exposed to the bottom 3 is formed by a synergistic effect with the bulk, and a stable submarine area suitable for the bottom of the clam larvae 5 and the like is provided by the surrounding gap. In addition, the gap increases the porosity of the bottom sediment, leads to appropriate water flow, and actively supplies oxygen and nutrient salts to ensure the growth of plankton and the like that feed the clam larvae 5.

散布によって水底３に豊富に露出する底質改善基材２は、図１に示すように、アサリの繁殖期において水中を浮遊するアサリの幼生等５に見付けられやすく、砂１等よりも大きく、安定した底質改善基材２が、小石等に代替する着底対象として選択できるようになる。底質改善基材２は表面が粗面であるために、アサリの幼生等５が着底に際して足糸１１を付着させることも容易である。アサリの幼生等５は、適宜底質改善基材２の端まで移動すれば、底質改善基材２、２間の間隙を埋める砂１等に潜り、着底を完了することができる。後述する発明者の実験によれば、このように底質改善基材２の多数を散布したことにより、散布しないときに比べて、アサリの稚貝５の水底３における採取数が大きく向上したことが確認された。   As shown in FIG. 1, the bottom sediment improvement base material 2 that is abundantly exposed to the water bottom 3 by spraying is easily found in the clam larvae 5 that float in the water during the clam breeding season, and is larger than the sand 1 etc. The stable bottom quality improving base material 2 can be selected as a bottoming target to be replaced with pebbles or the like. Since the bottom quality improving base material 2 has a rough surface, it is easy for the clam larvae 5 and the like 5 to attach the foot thread 11 when the bottom settles. If the clam larvae 5 move to the end of the bottom quality improving base material 2 as appropriate, they can dive into the sand 1 that fills the gap between the bottom quality improving base materials 2 and 2 and complete the bottoming. According to the experiment of the inventor described later, the number of samples collected at the bottom 3 of the clam larvae 5 is greatly improved by spraying a large number of the bottom sediment improving base material 2 in this way, compared to when not spraying. Was confirmed.

一方、底質改善基材２が散布される干潟の潮間帯付近にはアサリ以外にホトトギスガイも多く生息しており、繁殖期が重なったときにはホトトギスガイの幼生等が底質改善基材２に着底することによってアサリの幼生等５の着底を妨げることも想定される。このような場合には、貝殻の分量を減らすなどして底質改善基材２、２同士の癒着を適宜抑制しておけば、個々の底質改善基材２は円柱形状であるために水流を受けて水底３上を多少転がりやすくなり、これにより着底後に移動できないホトトギスガイの幼生等の成長を妨げ、移動できるアサリの幼生等５の成長を優先させることができる。   On the other hand, in addition to clams, many mussels live near the intertidal zone of the tidal flat where the bottom sediment improvement base material 2 is sprayed, and when the breeding seasons overlap, It is also assumed that the bottoming of the clam larvae 5 etc. is prevented by the bottoming. In such a case, if the adhesion between the bottom sediment improvement base materials 2 and 2 is appropriately suppressed by reducing the amount of shells or the like, each bottom sediment improvement base material 2 has a cylindrical shape, so In response to this, it becomes easier to roll on the water bottom 3, thereby preventing the growth of larvae of pearl mussels that cannot move after landing, and giving priority to the growth of larvae of clams that can move.

また、大型の低気圧などが襲来して水流が激しくなり、底質が層状に流動化しても、砂１等よりも嵩比重が小さい底質改善基材２はその後の静穏化、沈降によって水底表層部４に再度積み重ねられ、これによりアサリの幼生等５の着底を促進する水底３の安定した基質としての役割を維持することができる。さらに、発明者の実験によれば、上述した底質改善基材２、２同士の癒着はそれほど強固ではないため、仮にアサリ漁などの漁場に底質改善基材２を散布しても、アサリ漁に悪影響を与えることははない。   Moreover, even if a large low pressure strikes and the water flow becomes intense and the sediment is fluidized in layers, the sediment-improved base material 2 having a bulk specific gravity smaller than that of the sand 1 or the like is reduced by the subsequent calming and sedimentation. It is possible to maintain the role as a stable substrate of the water bottom 3 which is stacked again on the surface layer 4 and thereby promotes the bottoming of clams larvae 5 and the like. Furthermore, according to the inventor's experiment, the adhesion between the bottom sediment improvement base materials 2 and 2 described above is not so strong. Even if the bottom sediment improvement base material 2 is sprayed on a fishing ground such as clam fish, the clam There is no negative impact on fishing.

すなわち、一般にアサリ漁は、砂１等の中に潜るアサリの成貝を砂１等ごと適宜の籠ですくった後、籠を揺らして水で洗うようにして砂１等を落として成貝のみを得る。この籠はアサリの成貝の大きさに合わせて例えば２０ｍｍ以下のものが抜けるように形成される。したがって相互に癒着した底質改善基材２の多数が仮に籠ですくい上げられたとしても、籠を揺らしたときの震動によって癒着が解消し、個々の底質改善基材２は１０ｍｍ程度の長さに過ぎないために、この後、籠を抜けることができる。   In other words, in general, clams are fished only by scouring adult clams that are submerged in sand 1 etc. with 1 砂 of sand, etc. Get. This cocoon is formed so that, for example, 20 mm or less can be removed according to the size of the clam adult shellfish. Therefore, even if a large number of the bottom sediment improvement base materials 2 adhered to each other are scooped up with the cocoon, the adhesion is eliminated by the vibration when the heel is shaken, and each bottom sediment improvement base material 2 has a length of about 10 mm. After that, you can get out of the bag.

また、焼成によって形成される底質改善基材２は、容易に破損等することがなく、長期に渡ってアサリの増殖を促進することができる。長期間の経過にともなう砂１等の堆積によって底質改善基材２が水底３下に埋没したときには、耕耘をすればよく、耕耘によって砂１等とともに掘り起こされた底質改善基材２は、砂１等よりも小さい嵩比重よって水底表層部４に高い割合で露出する。さらに、原料が貝殻と粘土である底質改善基材２は、上述したように長期に水中に存在しても、自然環境に害を与える心配がない。   Moreover, the bottom material improving base material 2 formed by baking does not break easily, and can promote the growth of clams over a long period of time. When the sediment-improving base material 2 is buried under the water bottom 3 due to the accumulation of sand 1 or the like over a long period of time, it is only necessary to cultivate. Due to the bulk specific gravity smaller than that of sand 1 or the like, it is exposed at a high rate on the bottom surface layer portion 4. Furthermore, even if the bottom sediment improvement base material 2 whose raw material is a shell and clay exists in water for a long period of time as described above, there is no fear of harming the natural environment.

なお、以上においては、直径および長さが１０ｍｍ程度の円柱形状の底質改善基材２を用いる場合を示したが、沈降速度を考慮して適宜の形状、寸法、比重に変更することができる。底質改善基材２、２間に生じる隙間をアサリの幼生等５の潜砂領域にする場合でも、アサリの幼生等５は一般に殻長が５００μｍにも満たないため、上述した１０ｍｍ程度よりも小さな底質改善基材２を積み重ねたときに生じる隙間でも問題はない。また、上述したようにホトトギスガイの幼生等の増殖を適宜抑えるには、底質改善基材２が転がりやすい形状であれば足り、上述したように円柱形状以外に、例えば図２（ｃ）に示す截頭円錐形状でもほぼ同様の効果を期待できる。   In addition, although the case where the column-shaped bottom substance improvement base material 2 about 10 mm in diameter and length was used was shown above, it can be changed to an appropriate shape, size, and specific gravity in consideration of the sedimentation rate. . Even when the gap between the bottom sediment improving base materials 2 and 2 is used as a submarine sand area of clam larvae 5 and the like, the clam larvae 5 and the like generally have a shell length of less than 500 μm. There is no problem even with the gap generated when the small bottom material improving base materials 2 are stacked. Further, as described above, in order to appropriately suppress the growth of larvae of the mussel, it is sufficient if the bottom material improving base material 2 has a shape that easily rolls. As described above, for example, FIG. The same effect can be expected with the truncated cone shape shown.

さらに、以上においてはアサリの自然な繁殖によって生じた幼生等５の着底率を高め、その増殖を図る場合を示したが、飼育あるいは採取した幼生等５を底質改善基材２の散布領域に放流し、その着底を確保して増殖を図ることも可能である。   Furthermore, in the above, the case where the bottoming rate of the larvae etc. 5 generated by the natural breeding of clams is increased and the breeding is shown is shown. It is also possible to release it and to ensure its bottoming and to proliferate.

（実施例１）アサリの生息域である盤州干潟の潮間帯付近の水底において、２００６年１１月２日に上述した実施の形態に示す底質改善基材２の多数を岸から沖合に向かって長さ１ｍ、幅０．５ｍの範囲内に適宜積み重なるように散布し、同年１１月１４日、１２月７日のそれぞれにおいてその後の変化を確認した。底質改善基材２の比重、サイズは現地の波浪条件を考慮して適宜決定した。   (Example 1) At the bottom of the intertidal zone of Banshu Tidal Flat, which is a habitat for clams, many of the bottom sediment improvement base materials 2 shown in the above-mentioned embodiment on November 2, 2006 are headed offshore from the shore. Then, it was sprayed so as to be appropriately stacked within a range of 1 m in length and 0.5 m in width, and subsequent changes were confirmed on November 14 and December 7 of the same year. The specific gravity and size of the bottom quality improving base material 2 were appropriately determined in consideration of local wave conditions.

また、比較例１として粒径１０ｍｍの砂礫（砕石）を、比較例２としてサイズのみを直径５ｍｍ、長さ５ｍｍに変更したものを、比較例３として比重のみを１．５に変更したものを、比較例４として比重が１．５で、かつサイズが直径５ｍｍ、長さ５ｍｍであるものを同じ広さの範囲内でほぼ同様に多数が積み重なるように散布した。これらの比較例は実施例と同時に、それぞれの散布範囲が実施例の散布範囲と砂漣に対して平行になるように適宜隣接して並べた。   Further, as Comparative Example 1, gravel (crushed stone) having a particle size of 10 mm, as Comparative Example 2 only the size was changed to 5 mm in diameter and 5 mm in length, and as Comparative Example 3 only the specific gravity was changed to 1.5 As Comparative Example 4, a sample having a specific gravity of 1.5, a size of 5 mm in diameter, and a length of 5 mm was sprayed so that a large number of them were stacked in the same area. At the same time as the examples, these comparative examples were arranged adjacent to each other so that each spraying range was parallel to the spraying range of the example and the sand jar.

盤州干潟から比較的近く、当該海域における風浪条件を推定可能な千葉灯標における平均風速の経時変化を確認したところ、１１月７日にいわゆる爆弾低気圧が襲来したことなどにより、１１月２日から１２月７日までの期間中複数回にわたって秒速２０ｍ以上の風が確認された。したがって干潟の水底にはシートフローが生じていたことが推測される。   It was relatively close to the Banshu Tidal Flat, and the change in the average wind speed over time in the Chiba lightpost, which can estimate the wind conditions in the sea area, was confirmed. From December to December 7, winds of 20 m / s or more were confirmed several times. Therefore, it is presumed that a sheet flow occurred at the bottom of the tidal flat.

結果は、目視によれば１１月１４日、１２月７日のそれぞれの時点で、実施例１については多数を水底表面に確認することができた。また、１１月１４日、１２月７日のそれぞれの状況にほぼ変わりがないことが確認された。比較例１ないし４については１１月１４日の時点で既にほとんど確認することができなかった。強波浪により流失し、また早期に水底に埋没したことを確認している。   As a result of visual observation, a large number of Examples 1 were confirmed on the surface of the bottom of the water at each time of November 14 and December 7. In addition, it was confirmed that the situation on November 14 and December 7 was almost unchanged. In Comparative Examples 1 to 4, almost no confirmation was already possible as of November 14th. It has been confirmed that it was washed away by strong waves and buried at the bottom of the water at an early stage.

また、実施例１に関し、１２月７日の時点で、底質改善基材２同士が癒着し、全体として碁盤のようになっていることが確認された。なお、１１月１４日の時点については、当日の天候の都合上確認作業が目視のみとなったため、癒着について確認できていないが、上述したように目視において１２月７日の時点と比較してほとんど変化が認められなかったことから、この時に既に癒着が生じていたと考えられる。   Moreover, regarding Example 1, as of December 7, it was confirmed that the bottom sediment-improving base materials 2 were adhered to each other and looked like a grid as a whole. In addition, about the time of November 14, since the confirmation work became only visual for the convenience of the weather of the day, it was not able to confirm about adhesion, but compared with the time of December 7 visually as mentioned above. Since almost no change was observed, it is thought that adhesion had already occurred at this time.

さらに、その水底表面に露出する部位には珪藻が付着し、加えて、比較例１ないし４に比べて雑食性のヤドカリを範囲内により多く確認された。以上によれば、底質改善基材２の比重、サイズについて、散布域の状況に応じて適宜にその条件を選定することにより、干潟の水底の表面に長期に安定した基質を構築することができることが確認できた。また、生物親和性が良好で、生物多様性が実現されることも確認することができた。   Furthermore, diatoms adhered to the part exposed on the surface of the water bottom, and in addition, omnivorous hermit crab was confirmed more in the range than Comparative Examples 1 to 4. According to the above, it is possible to construct a stable substrate for a long time on the surface of the bottom of the tidal flat by selecting the conditions for the specific gravity and size of the bottom sediment improving base material 2 according to the condition of the spraying area. I was able to confirm that it was possible. It was also confirmed that bioaffinity was good and biodiversity was realized.

（実施例２）アサリの生息域である横浜の海の公園の潮下帯付近の適宜の水底において、２００６年１１月２日に上述した実施の形態に示す底質改善基材２の多数を１ｍ四方の範囲内に適宜積み重なるように散布し、同年１２月１５日のにおいてその後の変化を確認した。底質改善基材２の比重、サイズは現地の波浪条件を考慮して適宜決定されている。また、散布範囲である１ｍ四方の広さは、一般にアサリの稚貝の活動範囲と言われているため、アサリ幼生の着底地点との高い関連性が認められると推測される。   (Example 2) In an appropriate water bottom near the tide zone of a sea park in Yokohama, which is a habitat for clams, many of the bottom sediment improvement base materials 2 shown in the embodiment described above on November 2, 2006 are used. It sprayed so that it might pile up suitably within the range of 1m square, and the change after that was confirmed on December 15 of the same year. The specific gravity and size of the bottom quality improving base material 2 are appropriately determined in consideration of local wave conditions. In addition, since the area of 1m square, which is the spraying range, is generally said to be the activity range of clams larvae, it is estimated that there is a high relationship with the landing point of clams larvae.

この実施例においては、散布範囲内の任意の３箇所から二枚貝類の稚貝の出現状況をサンプリングするとともに、範囲外についても同様に任意の３箇所からサンプリングを行った。   In this example, the appearance status of bivalve larvae was sampled from arbitrary three locations within the spraying range, and was also sampled from arbitrary three locations outside the range.

結果を図３に示す。グラフから明らかなように、散布範囲内（基材内）で散布範囲外（基材外）に比して多くの二枚貝類の稚貝を確認することができた。また、散布範囲内で散布範囲外に比べて出現量が明らかに増大した二枚貝類の稚貝としては、アサリ以外に、ホトトギスガイについても確認された。以上によれば、底質改善基材の散布された範囲内で、アサリ漁場、ホトトギスガイ繁殖場が有効に創出されていることを確認することができた。なお、上記アサリやホトトギスガイ以外に、ムラサキガイやムールガイなどが含まれるイガイ科の貝についてもサンプリングでその出現が特定、確認された。   The results are shown in FIG. As is clear from the graph, many bivalve larvae could be confirmed in the spraying range (inside the base material) and out of the spraying range (outside the base material). In addition to clams, white mussels were also confirmed as clams of bivalves whose appearance amount was clearly increased in the spraying range compared to outside the spraying range. According to the above, it was confirmed that the clam fishing ground and the white mussel breeding ground were effectively created within the range where the bottom sediment improving base material was sprayed. In addition to clams and mussels, the occurrence of mussel shells including mussels and mussels was identified and confirmed by sampling.

底質改善基材の水底での状態、および二枚貝類の幼生等の着底行動を説明する図である。It is a figure explaining the state in the bottom of a bottom sediment improvement base material, and bottoming behavior, such as a bivalve larva. 底質改善基材を説明する図で、（ａ）は多数を水底に散布したときの状態を示す平面図、（ｂ）は単体の斜視図、（ｃ）は底質改善基材の変形例を示す斜視図である。It is a figure explaining a bottom quality improvement base material, (a) is a top view which shows a state when many are spread | dispersed on the water bottom, (b) is a single perspective view, (c) is a modification of a bottom quality improvement base material. FIG. 実施例２の結果を示すグラフである。10 is a graph showing the results of Example 2.

符号の説明Explanation of symbols

１ 砂
２ 底質改善基材
３ 水底
４ 水底表層部
５ 二枚貝類の幼生、稚貝 DESCRIPTION OF SYMBOLS 1 Sand 2 Base material improvement base 3 Water bottom 4 Water bottom surface layer 5 Bivalve larva and juvenile

Claims (4)

ほぼ粒状の底質改善基材の多数をアサリ等の二枚貝類の生息域における砂を含む水底に散布してアサリ等の二枚貝類の幼生、稚貝の着底を促してなり、
前記底質改善基材は、通常の波を受けてあまり移動しないとともに、強い波によってシートフローが生じた際に底質が液状化してなる層状の漂砂に埋もれることなく水底表層部をほぼ維持する１．１から１．７までの範囲内の嵩比重、および砂よりも嵩の張る大きさに、砕いた貝殻を比重調整材料として粘土に加えて成形、焼成することにより形成される二枚貝類の増殖方法。 Almost bivalves larvae of A Sari like by spraying the water bottom containing sand in bivalves habitat clams such a large number of bottom sediment improvement substrate granular, it was prompting wearing bottom of spats,
The bottom quality improving base material does not move much in response to normal waves, and substantially maintains the surface layer of the water bottom without being buried in the layered sand that is liquefied when the sheet flow is generated by strong waves. A bivalve that is formed by adding bulk specific gravity within the range of 1.1 to 1.7 and bulking it to a size that is more bulky than sand . Proliferation method. 前記底質改善基材は、粒径が２ｍｍから５０ｍｍの範囲内である請求項１記載の二枚貝類の増殖方法。 The method for breeding bivalves according to claim 1 , wherein the bottom material-improving substrate has a particle diameter in the range of 2 mm to 50 mm . １．１から１．７までの範囲内の嵩比重、および砂よりも嵩の張る大きさに、砕いた貝殻を比重調整材料として粘土に加えて成形、焼成して形成された底質改善基材。Sediment-improving group formed by molding and firing crushed shellfish in addition to clay as a specific gravity adjusting material to a bulk specific gravity in the range of 1.1 to 1.7 and bulky than sand Wood. 粒径が２ｍｍから５０ｍｍの範囲内である請求項３記載の底質改善基材。The bottom sediment-improving substrate according to claim 3, wherein the particle diameter is in the range of 2 mm to 50 mm.
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