JP3769535B2

JP3769535B2 - Cultivation of brown algae juveniles by exfoliation stirring method

Info

Publication number: JP3769535B2
Application number: JP2002359384A
Authority: JP
Inventors: 章生道家
Original assignee: KYOTO PREFECTURE
Current assignee: KYOTO PREFECTURE
Priority date: 2002-12-11
Filing date: 2002-12-11
Publication date: 2006-04-26
Anticipated expiration: 2022-12-11
Also published as: JP2004187574A

Description

【０００１】
【発明の属する技術分野】
本発明は、褐藻類を増養殖するための種苗を養成する方法に関し、特にホンダワラ等の固着性褐藻類の幼体を効率的に種苗として培養養成する方法に関するもので、海洋での褐藻類の養殖や藻場造成などに適用できる。
【０００２】
【従来の技術】
ホンダワラ、アラメなどに代表される褐藻類は、その優れた栄養価などにより、近年は特に現代人の健康増進食材として着目されて需要が高まりつつある。従来よりこのような褐藻類の増養殖を目的として種苗の生産が行われており、例えばブロック、石等、ロープ、網などの平板状もしくは紐状の基盤の上に胞子を播いた後、静止培養にて継続的に幼体を種苗として育成することが行われていた。また、中間育成後にブロック等に種苗が固着した状態のまま天然海域に出して養殖が行われていた。
【０００３】
【特許文献１】
特開平０６−６２６９０号公報
【特許文献２】
特開平１０−１７８９４７号公報
【特許文献３】
特開２００２−１７６８６６号公報
【０００４】
【発明が解決しようとする課題】
しかしながら、従来のような方法では、幼体が生育するに伴い基盤上で次第に過密となるため、光条件、栄養条件等が悪化することによる個体数の減少や生育不良に陥っていた。このため、初期段階の種苗を天然海域に沖出しせざるを得なくなり、それゆえ魚などの他の生物の捕食対象となる危険性が高く、その後の生残率は低くなるという問題が生じていた。また、生残率を向上させるために大型種苗まで生育させる場合、基盤上での密度を予め低く設定する必要があり、ゆえに面積当たりの種苗の生産効率が非常に悪くなるという問題があった。さらに、基盤に固着したままの種苗を天然海域に持ち出すので、種苗の搬出および設置に多大な量力を要していた。特にホンダワラ等の固着生褐藻類の場合、胞子が基盤に着生してから収穫まで２年弱の年数が必要であることがわかっている。従来の方法では天然海域に持ち出してからの期間が長くなるために、持ち出した後の生残率がとりわけ低かった。
【０００５】
褐藻類の幼体を培養する方法として、例えば上記の特許文献が挙げられる。
特許文献１は褐藻類の種苗育成に関するもので、初期の胞子体に一定強度の紫外線を照射し、培養することにより種苗を育成する方法が開示されている。特許文献２は海藻類の養殖装置および養殖方法に関するもので、基盤上に付着させ静止状態で培養した海藻の幼芽に特定波長の光を照射することにより、幼芽の生育を促進させる方法が開示されている。また、特許文献３は海藻の養殖に関するもので、胞子集塊や発芽集塊を形成させて培養する方法が開示されている。
【０００６】
しかしながら、特許文献１および特許文献２に記載の方法はいずれも種苗生産を種苗糸や基盤上で実施しているため、種苗の生長に伴って基盤上で過密状態に陥るという根本的な問題を解消できない。特許文献３は基盤を用いないで培養する方法であるが、培養開始前に胞子どうしを連結させて集塊を形成させるという煩雑な工程を必要としている。しかもこのような集塊は、複数の個体が過密に結合している状態なので、各個体の生長および生存に最も影響する個体間の競合を排除できないという問題がある。さらに、この方法は生殖細胞の連結が不可能な海藻（例えばホンダワラ科の海藻）には適用できないという決定的な不都合がある。
【０００７】
本発明は、あらゆる褐藻類の幼体を種苗として効率的に養成することを可能とする、全く新規な培養育成方法を提供することを課題とする。
【０００８】
【課題を解決するための手段】
本発明は、鋭意検討を重ねた結果、基盤上に胞子を高密度に播種し一定期間育成することで得られる幼体を基盤から剥離した後、この幼体を水槽に移して、水槽内で各幼体が浮遊する状態で培養することにより上記の問題点や不都合を解消できることを見出し、本発明を完成させるに至った。
【０００９】
すなわち、本発明は、褐藻類の幼体を種苗として培養養成する方法であって、以下の工程：（ａ）褐藻類の胞子または幼胚を基盤上に播種し幼体に培養する工程、（ｂ）前記幼体を前記基盤から剥離する工程、および（ｃ）前記剥離された幼体を水槽に移し、各幼体単独での浮遊状態を維持できるように海水注水およびエアレーションにより水槽内を攪拌しながら培養する工程、を含むことを特徴とする方法である。
【００１０】
このような方法であれば、水槽内で自由に浮遊する各幼体に対して、光照射や栄養を均一条件で提供しながら培養できるので、従来からの基盤上での静置培養法で生じる種苗の過密化を容易に回避できることとなり、種苗の減耗を大幅に減らせることとなる。また、水槽内で攪拌培養する幼体は、基盤から剥離されたものをそのまま水槽に移すだけでよいので、例えば胞子等の集塊を形成するなどの煩雑な手順を必要としない簡便な方法であるといえる。それゆえ、生殖細胞どうしの連結が不可能な海藻も含め、全ての褐藻類（アラメ、コンブ、ワカメなどを含む）の種苗養成に適用できることとなる。
【００１１】
また、本発明は、水槽内の培養の工程において、相対光強度を段階的に高める調整および前記水槽内の種苗の密度を段階的に減少させる調整を行うことを特徴とする方法である。
【００１２】
このような方法であれば、幼体の生長段階に応じて光条件を調節し、好適な種苗密度を維持できることとなるため、大型の種苗にまで養成することが可能となる。また、光条件に関しては、培養初期では光を抑え、幼体の生長に従って高めていくことが好ましく、例えば初期の相対光強度を約５％程度に設定し、後に約１０％へと段階的に上昇させることが望ましい。
【００１３】
さらに本発明は、前記幼体を水槽内で少なくとも主枝および中央葉が伸長する段階まで培養することを特徴としている。このような藻体であれば、種苗として天然海域に持ち出した場合の生残率を格段に高められることとなる。
【００１４】
また本発明は、上述の培養養成方法において用いられる前記水槽の底部にエア供給部が設けられ、かつ該底部は中心方向に傾斜するすり鉢形状を有していることを特徴とするものである。
【００１５】
また本発明は、前記褐藻類がホンダワラ科の藻類であることを特徴とする培養養成方法である。
【００１６】
【発明の実施の形態】
次に、図面に示す具体的な実施例に基づいて、本発明を更に詳細に説明する。
【００１７】
〔幼体の育成例〕
本発明の培養養成法に用いられる幼体の育成は、一般的な育成方法により行われる。以下では、ホンダワラを具体例に挙げて詳細に説明する。まず、ホンダワラの成熟期間である３月中旬から４月上旬頃に、生殖器床上に卵を付着させた雌の藻体（母藻）を採集し、流水下に静置しておく。数日程度で生殖器床上で卵が幼胚（長径約２５０〜３００μｍ）となった後に落下するので、これらを回収してメッシュで不要物を除去し、数回清浄な濾過海水で洗浄した後、屋外水槽内に載置した市販の建築用コンクリートブロック（約２００ｍｍ×４００ｍｍ×１００ｍｍ）上に幼胚を散布し、流水下で育成する。育成場所は、遮光幕により相対光強度（直射日光下での光量子量に対するその場の光量子量の割合）を約２％程度に調整し、この状態で約２〜３カ月育成させて幼体を得る。
【００１８】
〔幼体の剥離〕
幼体の剥離方法を概略的に示した斜視図である図１を参照して説明する。上述の幼胚は育成約２カ月で偏圧した単葉の初期葉が形成されたＳｔａｇｅ０の状態（全長約０．５〜１ｍｍ）の幼体１となる。コンンクリートブロック３上に固着したこの段階の幼体１を、図１に示すように、スクレーパー２等の道具を用いてコンクリートブロック３から仮根の部分から強制的に剥離する。剥離作業の際に、幼体１にできるだけ損傷を与えないように、慎重にブロック３表面を削り取る必要がある。なお、幼体を剥離して水槽に移す時期は上記に限られず他の生育段階でも可能であるが、ブロック上で生育し続けると過密状態になって死滅数が増大するため、Ｓｔａｇｅ０の段階の幼体を後述の攪拌培養の工程に移行することが望ましい。
【００１９】
〔攪拌培養装置〕
次に、攪拌培養装置の概略的な斜視図である図２を参照して説明する。剥離採取したＳｔａｇｅ０状態の幼体１を、図２に示すような、透明部材からなる円筒型の水槽５（約５０リットル容量）を具備する攪拌培養装置４に移動する。この水槽５の底部６の中心付近にはエア供給部７が設けられ、水槽５内に収容された幼体１がエアレーションにより水槽５内全体で穏やかに攪拌されるようになっている。さらに、海水供給部８と海水排出部９が設けられており、水面上方より注水しながら流水下で幼体１を育成できるように構成されている。この水槽５の底部６の形状は特に限定されないが、エアレーションによる攪拌効率を考慮すると中心方向に傾斜するすり鉢形状のものが望ましい。
【００２０】
〔攪拌培養方法〕
まず、海水で満たした攪拌培養装置４の水槽５内に、上述の剥離により得られたＳｔａｇｅ０の幼体１を約３０〜２００本／リットル、好ましくは約５０本／リットルの密度で収容し、遮光幕により相対光強度約５％程度に調整した状態でエアレーションを行いながら流水下にて攪拌培養する。なお、幼体の早い段階で相対光強度を約１０％にすると、付着珪藻などの他の藻類が繁茂してしまうので、暫くの期間（約２カ月間）は相対光強度約５％条件を維持することが好ましい。その後、種苗の成長に応じて光条件を相対光強度約１０％に上げて、かつ収容密度を段階的に低下させた条件で攪拌培養していく。
【００２１】
約２カ月後に、茎と双葉の初期葉が形成されたＳｔａｇｅＩの状態（全長約１〜５ｍｍ）まで育成した藻体を、相対光強度約１０％の場所に設置した攪拌培養装置４に移し、約１０〜１００本／リットル、好ましくは約２０本／リットルの密度となるように収容して同様の方法でさらに攪拌培養する。
【００２２】
次に、約２カ月の培養後に、へら状の葉が形成されたＳｔａｇｅＩＩの状態（全長約５〜１５ｍｍ）まで育成した藻体を、相対光強度約１０％の場所に設置した培養装置４に、約５〜２０本／リットル、好ましくは約１０本／リットルの密度となるように収容して同様の方法でさらに攪拌培養する。
【００２３】
約２カ月の培養後に、主枝のやや伸長したＳｔａｇｅＩＩＩの状態（全長約１５〜３０ｍｍ）まで育成した藻体を、相対光強度約１０％の場所に設置した培養装置４に、約３〜１０本／リットル、好ましくは約５本／リットルの密度となるように収容して同様の方法で引き続き攪拌培養する。
【００２４】
約４カ月の培養後に、複数の主枝の形成したＳｔａｇｅＩＶ‐１の状態（全長約３０〜５０ｍｍ）まで育成した藻体を、相対光強度約１０％の場所に設置した培養装置４に、約１〜３本／リットル、好ましくは約１本／リットルの密度となるように収容して同様の方法で引き続き攪拌培養する。
【００２５】
ＳｔａｇｅＩＶ‐１の種苗は、約４カ月後の段階で主枝の伸長したＳｔａｇｅＩＶ‐２の状態（全長約５０〜２００ｍｍ）を経て、気胞の形成されたＳｔａｇｅＶの状態（全長約２００ｍｍ以上）まで育成され、海域での増養殖用の種苗として仕立てられる。
【００２６】
なお、培養装置における注水条件は特に限定しないが、水槽内の水温が外気条件の変動に影響されないように、１回転／時間の条件（水槽内の海水が一時間で略入れ替わる条件）が好ましい。培養装置４を用いた攪拌培養は所定の光条件が得られる屋根付き屋外施設で実施するのが最適であるが、屋根がない場合でも遮光幕で光条件を調整することによって実施可能である。
【００２７】
〔種苗の利用〕
本発明の方法により得られる種苗を養殖等に使用する場合を図３を参照して説明する。上記のＳｔａｇｅＶの状態（全長約２００ｍｍ以上）まで養成した種苗１０を、天然海域に持ち出し、海中に設置した漁網に固定して養殖等に使用する。漁網の形状は特に限定されないが、特に、筒状にした漁網１１に固定して海中で延縄式養殖を実施するのが好ましい。図３Ａに、種苗１０を網１１に固定した状態を概略的に示し、Ｘ−Ｘ線での断面図を図３Ｂに示した。この場合、図３Ａおよび図３Ｂに示すように、網目（目合いが約３〜４ｃｍ）から種苗１０の主枝の上部のみを出すようにして、種苗下部の葉が引っ掛かることにより種苗１０を固定する。この方法は、種苗を直接ロープに挟み込む従来の固定方法と比べて、ロープと接触する種苗が擦れて流出する原因を排除することができるのでとりわけ望ましい。また、天然海域での藻場造成を行う場合も同様の方法で固定して実施することが可能である。
【００２８】
以下に実施例を挙げて本発明をより詳細に説明するが、以下の実施例によって本発明が限定されるものではない。
【００２９】
〔実施例１〕
６月〜８月：
コンクリートブロック上で平均全長約０．５〜５ｍｍまで育成したＳｔａｇｅ０の幼体（４月採苗）をブロックから剥離し、攪拌培養装置の５０リットル水槽内に約２，５００本の幼体を収容し、相対光強度が約５％の条件下で培養を開始した。上方の海水供給部より注水し、下方のエア供給部よりエアレーションを行い水槽内全体が穏やかに攪拌される状態で種苗の培養を開始した。８月には、平均全長約１ｍｍの藻体（ＳｔａｇｅＩ）に生長した。
【００３０】
８月〜１０月：
上記のＳｔａｇｅＩの藻体の約１，０００本を、５０リットル水槽内に収容し、相対光強度が約１０％の条件下で攪拌培養を続行した。１０月には、平均全長約１５ｍｍの藻体（ＳｔａｇｅＩＩ）に生長した。
【００３１】
１０月〜１２月：
上記のＳｔａｇｅＩＩの藻体の約５００本を、５０リットル水槽内に収容し、相対光強度が約１０％の条件下で攪拌培養を続行した。１２月には、全長が約１５〜３０ｍｍの藻体（ＳｔａｇｅＩＩＩ）に生長した。
【００３２】
１２月〜４月：
上記のＳｔａｇｅＩＩＩの藻体の約２５０本を、５０リットル水槽内に収容し、相対光強度が約１０％の条件下で引き続き攪拌培養した。４月には、全長が約３０〜５０ｍｍの藻体（ＳｔａｇｅＩＶ‐１）に生長した。
【００３３】
４月〜８月：
上記のＳｔａｇｅＩＶ‐１の藻体の約２５本を、２５リットル水槽内に収容し、相対光強度が約１０％の条件下で引き続き攪拌培養した。藻体は順調に生長して６月〜８月には、平均全長約２０ｃｍの藻体（ＳｔａｇｅＶ）に生長し、天然海域での増養殖用の種苗に仕上げられた。実施例１の培養工程を以下の表１に要約する。
【００３４】
【表１】

【００３５】
実施例１で得られた種苗を８月に天然海域（水深３ｍ）に持ち出し、上述の要領で筒状の網に固定して養殖を行ったところ、翌年１月において全長約１８０〜２２０ｃｍまで良好に生育していた。またこの時の種苗の生残率は約９６％以上であることが確認された。
【００３６】
（本発明の培養養成法と従来法との比較‐１：収量の比較）
本発明の培養養成法と従来の静置培養法の比較を行った。平均全長約６〜８ｍｍの段階の種苗を用い、培養に要する底面積あたりの種苗の増重量を評価した。その結果、攪拌培養装置を用いて立体的に培養する本発明の培養養成法では、静置培養法の約４〜５倍もの種苗を収容して培養できることが明らかになった。
【００３７】
（本発明の培養養成法と従来法との比較‐２：生長促進効果）
従来法に従いコンクリートブロック上でＳｔａｇｅＩの段階まで静置培養した藻体を種苗として、コンクリートブロックに固着したまま状態で８月に沖出し（天然海域の水深３ｍ）したところ、翌年２月における全ての種苗はＳｔａｇｅＩＩの段階に生長していた。一方、幼体を剥離して水槽に移した本発明の培養養成法では、翌年２月における種苗は全てＳｔａｇｅＩＩＩの段階まで生長していた。本発明では水槽内を攪拌しながら培養するため、水槽内を浮遊し回転する種苗が満遍なく光を受けることが可能となって生長が促進されたと推測された。またさらに、種苗を選抜して水槽内の密度を減らしながら本発明の方法により培養すれば、ＳｔａｇｅＩＶ‐１の段階まで生長が促進されることが確認され、本発明の培養養成法の優れた生長促進効果が示された。
【００３８】
〔実施例２〕
上述の幼体の育成例に従い、コンクリートブロック上で種苗を７月まで育成した後、攪拌培養装置に移行させて相対光強度２〜５％の環境において９月まで約２カ月間培養した。得られた種苗の本数を計測して生残率を算出した。比較例として、コンクリートブロック上で（上記と同じ相対光強度の環境下）９月まで継続して種苗を静置培養し、生残率を算出した。
【００３９】
７月の段階で６０００本あった種苗は、実施例２の攪拌培養後において約３６００本となり、その生残率は約６０％であった。一方、比較例の種苗は約１２００本となり、その生残率は約２０％であった。したがって、本発明の種苗培養方法によれば、従来方法よりも約３倍もの種苗を有効に利用できることが確かめられた。
【００４０】
なお、本発明は上述した実施例には限られない。例えば、５０リットルより大型の水槽を用いて培養することも可能である。水槽は円筒に限られず、立方体や球状でも構わない。また、全く透明な部材からなるものに限られず、光透過性を少なくとも有する部材を用いているものであればよい。
【００４１】
【発明の効果】
以上詳述したように、本発明の培養養成法によれば、水槽内で自由に浮遊する各幼体に対して、光照射や栄養を均一条件で提供しながら培養できるので、従来法の静置培養で起きる幼体の過密化を回避できるメリットがあり、種苗の育成過程での減耗を大幅に減少できるという効果を奏する。また、水槽内で攪拌培養する幼体は、基盤から剥離されたものをそのまま用いるだけなので、全ての褐藻類に適用できるという利点がある。本発明の培養養成法は、従来の静置培養法と比較して、培養水槽の底面積あたり約５倍もの幼体を収容し育成できるだけでなく、幼体自体の生長促進効果も有しており、種苗の生産効率に非常に優れる方法である。さらに本発明の方法は、高度な施設やバイオテクノロジー技術を必要としないので、低コストで効率的な種苗の大量培養を可能とする。天然母藻から採種、育成した幼体を用いるので、天然海域に持ち出しても天然海域本来の海藻類と遺伝的に変わず、自然に優しい養殖や藻場の形成が達成できるという効果も有する。
【図面の簡単な説明】
【図１】本発明の一実施例を図示すもので、コンクリートブロックに播種し育成させたホンダワラ幼体の剥離方法を概略的に示した斜視図である。
【図２】本発明の一実施例を図示すもので、種苗の養成に用いられる種苗培養装置の概略的な斜視図である。
【図３】ＳｔａｇｅＶまで養成した種苗を養殖に使用するために網に固定した状態を概略的に示した図であり、図３Ａは正面図、図３Ｂは、図３ＡにおけるＸ−Ｘ線の部分断面図である。
【符号の説明】
１幼体
２スクレーパー
３ブロック
４培養装置
５水槽
６底部
７エア供給部
８海水供給部
９海水排出部
１０種苗
１１網[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for cultivating seedlings and seedlings for enhancing aquaculture of brown algae, and more particularly to a method for efficiently cultivating seedling seedlings such as hondawala as seedlings and cultivating brown algae in the ocean. It can be applied to the creation of seaweed beds and seaweed beds.
[0002]
[Prior art]
In recent years, demand for brown algae typified by hondawala and arame has been increasing due to its excellent nutritional value, particularly as a health promotion ingredient for modern people. Conventionally, seedlings have been produced for the purpose of such aquaculture of brown algae. For example, after seeding spores on a flat or string-like base such as blocks, stones, ropes, nets, etc. It has been practiced to continuously grow young seedlings as seedlings in culture. In addition, after the intermediate breeding, the seedlings and seedlings were stuck to a block or the like, and were put out to the natural sea area and cultured.
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 06-62690 [Patent Document 2]
JP-A-10-178947 [Patent Document 3]
JP 2002-176866 A [0004]
[Problems to be solved by the invention]
However, in the conventional method, as the juvenile grows, it becomes gradually overcrowded on the base, so that the number of individuals and the growth failure occur due to deterioration of light conditions, nutritional conditions and the like. For this reason, there is a problem that the seeds and seedlings in the initial stage have to be offshore to the natural sea area, and therefore there is a high risk that they will be prey for other organisms such as fish, and the survival rate after that will be low. It was. In addition, when growing even large seedlings in order to improve the survival rate, it is necessary to set the density on the base low in advance, and thus there is a problem that the production efficiency of seedlings per area becomes very poor. Furthermore, since the seedlings that have been fixed to the base are taken out to the natural sea area, a large amount of force is required for carrying out and setting the seedlings. In particular, in the case of sticky brown algae such as Honda walla, it has been found that it takes less than two years from the time the spores settle on the base to harvest. In the conventional method, since the period after taking out to the natural sea area becomes long, the survival rate after taking out was particularly low.
[0005]
As a method for culturing brown algae juveniles, for example, the above-mentioned patent documents can be mentioned.
Patent Document 1 relates to seedling growth of brown algae, and discloses a method for growing seedlings by irradiating and culturing an early spore body with ultraviolet light having a certain intensity. Patent Document 2 relates to a seaweed aquaculture device and a culture method, and a method for promoting the growth of shoots by irradiating light of a specific wavelength onto the shoots of seaweed that are attached to a base and cultured in a stationary state. It is disclosed. Patent Document 3 relates to seaweed aquaculture, and discloses a method of culturing by forming spore clumps and germination clumps.
[0006]
However, since the methods described in Patent Document 1 and Patent Document 2 both carry out seedling production on seedling yarn and the base, there is a fundamental problem that the seedling is overcrowded on the base as the seedling grows. It cannot be resolved. Patent Document 3 is a method of culturing without using a substrate, but requires a complicated process of connecting spores to form a conglomerate before the start of culture. Moreover, since such an agglomeration is in a state in which a plurality of individuals are closely connected, there is a problem that competition between individuals that most affects the growth and survival of each individual cannot be excluded. Furthermore, this method has a decisive disadvantage that it cannot be applied to seaweeds in which germ cells cannot be connected (for example, seaweeds of the family Hawkidae).
[0007]
It is an object of the present invention to provide a completely new culture and growth method that makes it possible to efficiently cultivate all brown algae juveniles as seedlings.
[0008]
[Means for Solving the Problems]
As a result of intensive studies, the present invention has separated larvae obtained by seeding spores on a base at a high density and growing them for a certain period of time, and then transferred the pups to the aquarium. It was found that the above-mentioned problems and inconveniences can be solved by culturing in a floating state, and the present invention has been completed.
[0009]
That is, the present invention is a method for culturing and cultivating brown algae seedlings as seedlings, and comprises the following steps: (a) a step of seeding brown algae spores or embryos on a base and culturing the seedlings; A step of detaching the juvenile from the base, and (c) a step of transferring the peeled juvenile to a water tank and culturing the water tank with stirring by seawater injection and aeration so as to maintain a floating state of each juvenile alone. The method characterized by including.
[0010]
With such a method, each seedling that floats freely in the aquarium can be cultured while providing light irradiation and nutrition under uniform conditions, so the seedlings and seedlings produced by the conventional stationary culture method on the base Overcrowding can be easily avoided, and seedling loss can be greatly reduced. In addition, juveniles that are agitated and cultured in the water tank are simple methods that do not require complicated procedures such as forming agglomerates such as spores, since it is only necessary to transfer the peeled pieces from the base to the water tank. It can be said. Therefore, it can be applied to seed and seedling cultivation of all brown algae (including arame, kombu, wakame, etc.) including seaweeds in which germ cells cannot be connected.
[0011]
Further, the present invention is a method characterized in that in the step of culturing in the aquarium, an adjustment for increasing the relative light intensity in stages and an adjustment for decreasing the density of seedlings in the aquarium in stages are performed.
[0012]
With such a method, the light conditions can be adjusted according to the growth stage of the juvenile and a suitable seedling density can be maintained, so that even large seedlings can be trained. As for the light conditions, it is preferable to suppress the light at the initial stage of culture and increase it according to the growth of the juvenile. For example, the initial relative light intensity is set to about 5% and then gradually increases to about 10%. It is desirable to make it.
[0013]
Furthermore, the present invention is characterized in that the juvenile is cultured in a water tank to a stage where at least main branches and central leaves extend. If it is such an algal body, the survival rate at the time of carrying out to a natural sea area as a seedling will be raised markedly.
[0014]
Further, the present invention is characterized in that an air supply unit is provided at the bottom of the water tank used in the culture and cultivation method described above, and the bottom has a mortar shape inclined in the central direction.
[0015]
In addition, the present invention is the culture and cultivation method, wherein the brown algae is an algae of the family A.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Next, the present invention will be described in more detail based on specific embodiments shown in the drawings.
[0017]
[Examples of juvenile rearing]
The growth of juveniles used in the culture cultivation method of the present invention is carried out by a general breeding method. In the following, a detailed description will be given using a Honda walla as a specific example. First, the female alga bodies (maternal algae) with eggs attached to the genital bed are collected from mid-March to early April, which is the maturity period of Honda Walla, and left standing under running water. Since eggs fall after they become young embryos (major axis: about 250-300 μm) on the genital floor in a few days, these are collected and removed unnecessary matter with a mesh, washed several times with clean filtered seawater, A young embryo is sprayed on a commercially available concrete block for construction (about 200 mm × 400 mm × 100 mm) placed in an outdoor water tank and grown under running water. The breeding place is adjusted to about 2% relative light intensity (ratio of photoquantity in situ to photoquantity under direct sunlight) using a light-shielding curtain, and grown in this state for about 2 to 3 months to obtain a young body .
[0018]
[Peeling of juveniles]
A method for peeling a young body will be described with reference to FIG. The above-mentioned young embryo becomes a juvenile 1 in a Stage 0 state (total length: about 0.5 to 1 mm) in which a single-leaf initial leaf biased in about 2 months is formed. As shown in FIG. 1, the young body 1 fixed at this stage on the concrete block 3 is forcibly separated from the temporary root portion from the concrete block 3 using a tool such as a scraper 2. During the peeling operation, it is necessary to carefully scrape the surface of the block 3 so as not to damage the young body 1 as much as possible. Note that the time when the juveniles are peeled off and transferred to the aquarium is not limited to the above, but can be in other growth stages. However, if they continue to grow on the block, they become overcrowded and the number of deaths increases. It is desirable to shift to a stirring culture process described later.
[0019]
[Stirring culture equipment]
Next, description will be made with reference to FIG. 2 which is a schematic perspective view of a stirring culture apparatus. The juvenile body 1 in the Stage 0 state, which has been peeled off, is moved to a stirring culture apparatus 4 having a cylindrical water tank 5 (approximately 50 liter capacity) made of a transparent member as shown in FIG. An air supply unit 7 is provided in the vicinity of the center of the bottom 6 of the water tank 5 so that the young body 1 accommodated in the water tank 5 is gently agitated throughout the water tank 5 by aeration. Furthermore, the seawater supply part 8 and the seawater discharge part 9 are provided, and it is comprised so that the young body 1 can be raised under flowing water, pouring water from the upper surface of a water surface. The shape of the bottom 6 of the water tank 5 is not particularly limited, but a mortar shape that is inclined in the center direction is desirable in consideration of the stirring efficiency by aeration.
[0020]
[Stirring culture method]
First, Stage 0 juveniles 1 obtained by the above-described separation are accommodated in a water tank 5 of a stirring culture apparatus 4 filled with seawater at a density of about 30 to 200 / liter, preferably about 50 / liter, and are shielded from light. The agitation is performed under running water while aeration is performed with the relative light intensity adjusted to about 5% by the curtain. If the relative light intensity is increased to about 10% at an early stage of the juvenile, other algae such as attached diatoms will thrive, so the condition of relative light intensity of about 5% is maintained for a short period (about 2 months). It is preferable to do. Thereafter, the light conditions are increased to a relative light intensity of about 10% in accordance with the growth of the seedlings, and the agitation culture is performed under the conditions where the accommodation density is gradually reduced.
[0021]
About 2 months later, the algal bodies grown to the Stage I state (total length: about 1 to 5 mm) in which the stems and twin leaves were formed were transferred to the agitation culture apparatus 4 installed in a place with a relative light intensity of about 10%. It is accommodated at a density of about 10 to 100 / liter, preferably about 20 / liter, and further stirred and cultured in the same manner.
[0022]
Next, after culturing for about 2 months, the algal cells grown to the stage II state (total length: about 5 to 15 mm) in which a spatula-like leaf is formed are placed in the culture apparatus 4 installed at a place where the relative light intensity is about 10%. In a similar manner, the mixture is further stirred and cultured with a density of about 5 to 20 lines / liter, preferably about 10 lines / liter.
[0023]
After culturing for about 2 months, the algal bodies grown to a slightly elongated Stage III state (total length: about 15-30 mm) of the main branch are placed in the culture apparatus 4 installed at a location where the relative light intensity is about 10%, about 3-10. It is housed at a density of about 5 liters / liter, preferably about 5 liters / liter, and is subsequently stirred and cultured in the same manner.
[0024]
After culturing for about 4 months, the algal bodies grown to the stage IV-1 state (total length: about 30 to 50 mm) formed with a plurality of main branches are placed in the culture apparatus 4 installed at a place where the relative light intensity is about 10%. It is housed in a density of 1 to 3 tubes / liter, preferably about 1 tube / liter, followed by stirring and culturing in the same manner.
[0025]
Stage IV-1 seedlings grow to a Stage V state (over 200 mm or more in length) in which the main branches are extended through Stage IV-2 (overall length: about 50 to 200 mm) after about 4 months. And tailored as seedlings for aquaculture in the sea.
[0026]
In addition, although the water injection conditions in the culture apparatus are not particularly limited, a condition of one rotation / hour (a condition in which seawater in the water tank is substantially replaced in one hour) is preferable so that the water temperature in the water tank is not affected by fluctuations in outside air conditions. Stirring culture using the culture apparatus 4 is optimally performed in an outdoor facility with a roof where predetermined light conditions can be obtained, but even when there is no roof, it can be performed by adjusting the light conditions with a light-shielding curtain.
[0027]
[Use of seedlings]
The case where the seedling obtained by the method of the present invention is used for aquaculture etc. will be described with reference to FIG. The seedling 10 that has been cultivated to the above Stage V state (total length of about 200 mm or more) is taken out to a natural sea area, fixed to a fishing net installed in the sea, and used for aquaculture. The shape of the fishing net is not particularly limited, but it is particularly preferable to carry out longline culture in the sea by fixing it to the cylindrical fishing net 11. FIG. 3A schematically shows a state in which the seedling 10 is fixed to the net 11, and a cross-sectional view taken along line XX is shown in FIG. 3B. In this case, as shown in FIGS. 3A and 3B, only the upper part of the main branch of the seedling 10 is taken out from the mesh (mesh is about 3 to 4 cm), and the seedling 10 is fixed by catching the leaf of the lower part of the seedling. To do. This method is particularly desirable because it can eliminate the cause of the seedlings coming into contact with the rope from rubbing and flowing out, as compared with the conventional fixing method in which the seedlings are directly sandwiched between the ropes. In addition, when a seaweed bed is created in a natural sea area, it can be fixed in the same manner.
[0028]
The present invention will be described in more detail with reference to examples below, but the present invention is not limited to the following examples.
[0029]
[Example 1]
June to August:
Stage0 juveniles (April seedlings) grown to an average total length of about 0.5 to 5 mm on a concrete block were detached from the block, and about 2,500 juveniles were accommodated in a 50 liter water tank of a stirring culture apparatus. The culture was started under the condition that the relative light intensity was about 5%. Water was poured from the upper seawater supply section, aeration was performed from the lower air supply section, and seedling seedling culture was started in a state where the entire water tank was gently stirred. In August, they grew into alga bodies (Stage I) having an average total length of about 1 mm.
[0030]
August to October:
About 1,000 of the above-mentioned Stage I alga bodies were accommodated in a 50-liter water tank, and the stirring culture was continued under the condition that the relative light intensity was about 10%. In October, they grew into alga bodies (Stage II) with an average total length of about 15 mm.
[0031]
October to December:
About 500 of the above-mentioned Stage II algal bodies were accommodated in a 50-liter water tank, and the stirring culture was continued under the condition that the relative light intensity was about 10%. In December, they grew into alga bodies (Stage III) with a total length of about 15-30 mm.
[0032]
December to April:
About 250 of the above-mentioned Stage III alga bodies were placed in a 50 liter water tank and subsequently stirred and cultured under conditions of a relative light intensity of about 10%. In April, they grew into alga bodies (Stage IV-1) with a total length of about 30-50 mm.
[0033]
April to August:
About 25 of the above-mentioned Stage IV-1 alga bodies were placed in a 25-liter water tank and subsequently cultured under stirring under a condition where the relative light intensity was about 10%. The alga body grew smoothly, and from June to August, it grew to an alga body (Stage V) having an average total length of about 20 cm, and finished as a seedling for augmentation culture in a natural sea area. The culture process of Example 1 is summarized in Table 1 below.
[0034]
[Table 1]

[0035]
The seedlings obtained in Example 1 were taken out to the natural sea area (water depth of 3 m) in August, and fixed to a cylindrical net as described above, and then cultivated. In January of the following year, the total length was about 180 to 220 cm. It was growing. Moreover, it was confirmed that the survival rate of seedlings at this time was about 96% or more.
[0036]
(Comparison of culture cultivation method of the present invention and conventional method-1: Comparison of yield)
The culture cultivation method of the present invention was compared with the conventional static culture method. Using seedlings at an average total length of about 6 to 8 mm, the weight increase of seedlings per bottom area required for culture was evaluated. As a result, it has been clarified that the culture cultivation method of the present invention in which three-dimensional culture is performed using a stirring culture device can accommodate and cultivate seedlings that are about 4 to 5 times as many as the stationary culture method.
[0037]
(Comparison between the culture and cultivation method of the present invention and the conventional method-2: Growth promotion effect)
According to the conventional method, the algal bodies that were statically cultured on the concrete block until the Stage I stage were used as seedlings, and then offshore in August while remaining fixed to the concrete block (3m deep in the natural sea area). The seedlings grew at the Stage II stage. On the other hand, in the culture cultivation method of the present invention in which the juveniles were peeled and transferred to the water tank, all seedlings in February of the following year were grown to the stage III stage. In the present invention, since the inside of the aquarium was cultured while stirring, it was speculated that the seedlings that floated and rotated in the aquarium could receive light uniformly and promoted growth. Furthermore, if seeds and seedlings are selected and cultured by the method of the present invention while reducing the density in the water tank, it is confirmed that the growth is promoted to the stage IV-1 stage, and the excellent growth of the culture cultivation method of the present invention is confirmed. The promotion effect was shown.
[0038]
[Example 2]
In accordance with the above-described example of juvenile growth, seedlings were grown on a concrete block until July, then transferred to a stirring culture apparatus and cultured for about 2 months in September in an environment with a relative light intensity of 2 to 5%. The number of seedlings obtained was measured to calculate the survival rate. As a comparative example, seedlings were statically cultured on a concrete block (under the same relative light intensity environment as described above) until September, and the survival rate was calculated.
[0039]
The seedlings and seedlings, which were 6000 at the July stage, were about 3600 after the stirring culture in Example 2, and the survival rate was about 60%. On the other hand, the number of seedlings of the comparative example was about 1200, and the survival rate was about 20%. Therefore, according to the seed and seedling culture method of the present invention, it was confirmed that about three times as many seedlings as the conventional method can be effectively used.
[0040]
In addition, this invention is not restricted to the Example mentioned above. For example, it is possible to culture using a water tank larger than 50 liters. The water tank is not limited to a cylinder, and may be a cube or a sphere. Moreover, it is not restricted to what consists of a completely transparent member, What is necessary is just to use the member which has a light transmittance at least.
[0041]
【The invention's effect】
As described above in detail, according to the culture and cultivation method of the present invention, each young body freely floating in the water tank can be cultured while providing light irradiation and nutrition under uniform conditions. This has the advantage of avoiding the overcrowding of juveniles that occurs in culture, and has the effect of greatly reducing depletion during seedling growth. Moreover, since the young body which carries out stirring culture in a water tank uses only what was peeled from the base | substrate as it is, there exists an advantage that it can apply to all the brown algae. The culture and cultivation method of the present invention not only accommodates and nurtures about 5 times as many larvae per bottom area of the culture tank as compared with the conventional stationary culture method, but also has the effect of promoting the growth of the larvae themselves, It is a method with excellent seed and seedling production efficiency. Furthermore, since the method of the present invention does not require advanced facilities or biotechnology techniques, it enables efficient mass cultivation of seedlings at low cost. Since juveniles seeded and grown from natural mother algae are used, even if they are brought out to the natural sea area, they do not change genetically from the natural seaweeds of the natural sea area, and there is an effect that it is possible to achieve natural-friendly aquaculture and formation of algae beds.
[Brief description of the drawings]
FIG. 1 is a perspective view schematically showing a method for peeling off a young carpenter seedling that has been sown and grown on a concrete block according to an embodiment of the present invention.
FIG. 2 is a schematic perspective view of a seedling culturing apparatus used for seedling cultivation, illustrating an embodiment of the present invention.
FIGS. 3A and 3B are diagrams schematically illustrating a state in which seedlings grown to Stage V are fixed to a net for use in aquaculture, FIG. 3A is a front view, and FIG. 3B is a portion along line XX in FIG. 3A. It is sectional drawing.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Young body 2 Scraper 3 Block 4 Culture apparatus 5 Water tank 6 Bottom part 7 Air supply part 8 Seawater supply part 9 Seawater discharge part 10 Seedling 11 Net

Claims

A method for cultivating brown algae seedlings as seedlings, comprising the following steps:
(A) a step of seeding brown algae spores or young embryos on a base and culturing them into young bodies;
(B) a step of peeling the juvenile from the base; and (c) transferring the peeled juvenile to a water tank and stirring the inside of the water tank by seawater injection and aeration so that the floating state of each juvenile can be maintained. A culture cultivation method comprising the step of culturing.

In the step of culturing in the aquarium, it is characterized by performing an adjustment to increase the ratio of the photon amount in situ with respect to the photon amount under direct sunlight and an adjustment to gradually decrease the density of seedlings in the aquarium. The culture cultivation method according to claim 1.

The culture cultivation method according to claim 1 or 2, further comprising culturing the juvenile in a water tank until at least a main branch and a central leaf extend.

The culture cultivation method according to any one of claims 1 to 3, wherein an air supply part is provided at a bottom part of the water tank, and the bottom part has a mortar shape inclined in a central direction. .

The culture cultivation method according to any one of claims 1 to 4, wherein the brown algae is an algae belonging to the family Aceraceae.