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マアナゴ(Conger myriaster)葉形仔魚の沿岸域への回遊機構に関する研究
https://fra.repo.nii.ac.jp/records/2010864
https://fra.repo.nii.ac.jp/records/20108640aa10f46-1fec-48d0-9a23-652ad0f49155
| 名前 / ファイル | ライセンス | アクション |
|---|---|---|
fra_k_24_105.pdf (1.3 MB)
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| Item type | 紀要論文 / Departmental Bulletin Paper(1) | |||||
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| 公開日 | 2024-10-02 | |||||
| タイトル | ||||||
| タイトル | マアナゴ(Conger myriaster)葉形仔魚の沿岸域への回遊機構に関する研究 | |||||
| 言語 | ja | |||||
| タイトル | ||||||
| タイトル | Study on the inshore migration mechanism of Conger myriaster leptocephali | |||||
| 言語 | en | |||||
| 言語 | ||||||
| 言語 | jpn | |||||
| キーワード | ||||||
| 言語 | en | |||||
| 主題Scheme | Other | |||||
| 主題 | Conger myriaster ; leptocephali; mtDNA; Kuroshio; inshore migration | |||||
| 資源タイプ | ||||||
| 資源タイプ識別子 | http://purl.org/coar/resource_type/c_6501 | |||||
| 資源タイプ | departmental bulletin paper | |||||
| アクセス権 | ||||||
| アクセス権 | open access | |||||
| アクセス権URI | http://purl.org/coar/access_right/c_abf2 | |||||
| 著者 |
黒木, 洋明
× 黒木, 洋明 |
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| 抄録 | ||||||
| 内容記述タイプ | Abstract | |||||
| 内容記述 | Conger myriaster is an important commercial fish species in Japan, Korea and China. The larvae have only been caught in shallow coastal areas, and most of them are large individuals （80-130 mm TL） at the late leptocephalus or metamorphic stage. Because of the lack of information on distributional ecology of small leptocephali, recruitment mechanism of C. myriaster has been a mystery in spite of many catches of large leptocephali in coastal areas. Because mature individuals have not been collected from inshore waters to continental slope where commercial fishing takes place, the spawning ground has been presumed to be in deeper offshore waters. The early life history of C. myriaster from spawning in offshore waters to their inshore migration remains unknown. The distributional pattern of leptocephali in the genus Conger was investigated around the Kuroshio, the Kuroshio Extension in the East China Sea and the western North Pacific in order to determine the inshore migration pattern of C. myriaster leptocephali. Conger leptocephali were collected along the Kuroshio, extended southerly to latitude 26° N near the Ryukyu Islands and northerly to 38° N of the Kuroshio-Oyashio transitional zone. The leptocephali were mainly caught in the mainstream and inshore side of the Kuroshio in areas south and north of latitude 29° N, respectively. Two types of C. myriaster leptocephali were recognized in a total of 211 leptocephali. External pigmentary features indicated 79 individuals were C. myriaster （Type A）, most of which were larger than 80 mm in total length （TL） and caught at low water temperature （<16℃）. Most of non-type A leptocephali （N=132） were smaller than 80 mm TL and caught at higher water temperature （16-26℃）, and 89.3% of randomly subsampled individuals （N=25） were identified as C. myriaster based on mitochondrial DNA analyses （Type B）. Thus, C. myriaster was estimated to occupy approximately 90% of the Conger leptocephali collected in this study. Negative relationships between TL and water temperature indicated that the inshore migration of C. myriaster leptocephali occurred along the thermal gradient from warm offshore Kuroshio areas （20- 26℃） to colder coastal areas （<16℃） with their growth; however, the mechanism of the inshore migration is still unclear. Generally, there is a negative relationship between temperature and density of sea water; therefore, the leptocephali should experience increasing environmental density during their inshore migration. It is not known whether the leptocephali, which are devoid of a swim bladder, regulate buoyancy. To examine the presence of buoyancy regulation of the leptocephali, the body density of live leptocephali caught from cold coastal areas in which sigma-t ranged from 25 to 26 （13-15℃） were measured. Repetitive measurements of the same specimens （N=10） revealed that the mean body relative density was higher in the day （1.029） than in the night （1.026）, indicating that the leptocephali actively regulate the body density diurnally. The body density of leptocephali at mid-night ranged from 1.025 to 1.028, and larger individuals had a higher density, indicating the increase in the body density with the body growth. The body density of the leptochphali is ascertained to be lower in the offshore areas before migration than in the coastal areas because sea water density in upper layer of the offshore Kuroshio in which the leptocephali maintain neutral buoyancy ranging from 1.023 to 1.024. Therefore, the leptocephali are considered to increase the body density through the inshore migration process. The ability of the larvae to regulate body density is important in controlling their migration from warm to cold water areas because of a negative relationship between seawater density and temperature. The findings of the present study suggest a hypothetical pathway of the migration in which the larvae vertically migrate into deeper depths to approach coastal areas. Simulations of larval dispersal or retention by hydrodynamic models should incorporate the information on larval body density fluctuation. | |||||
| 言語 | en | |||||
| 抄録 | ||||||
| 内容記述タイプ | Abstract | |||||
| 内容記述 | 本論文は、沿岸域から東シナ海および西部北太平洋の沖合・外洋域にいたる広範囲の海域での調査結果にもとづき、マアナゴ(Conger myriaster )葉形仔魚の沿岸域への出現様式と従来知見が無かった沖合・外洋域での分布生態を明らかにしたものである。また、葉形仔魚の沿岸域への回遊機構について、仔魚分布様式に海洋観測結果と飼育実験の結果を加えて検討し、マアナゴ葉形仔魚の沿岸来遊量の水準を海洋環境変動から予測する可能性を示すとともに、漁況予測に向けた技術開発について考察した。はじめに、Conger 属葉形仔魚の分類学的な問題点を整理し、従来用いられていた黒色素胞の沈着状態から分類する方法に加え分子生物学的な手法を取り入れて、マアナゴ葉形仔魚の同定法を確立した。次に、沖合・外洋域で採集されたConger 属葉形仔魚の約90%は、沿岸域に出現するマアナゴ葉形仔魚のもつ特徴的な色素胞を持たないにもかかわらず、分子生物学的な手法を用いるとマアナゴと同定されることを示し、これまで全く不明であった沖合・外洋域でのマアナゴ仔魚の分布特性を明らかにした。また、仔魚の沿岸域への出現時期と沿岸水温の関係を明らかにし、沖合での分布特性とあわせて、沖合の高水温域から西岸境界流フロントを越えて沿岸の低水温域へ至る回遊過程を示した。さらに、本種仔魚の全長・体重関係を解析し、沿岸への回遊過程に対応した成長様式を持つことを示すとともに、仔魚の耳石微細構造の観察結果から2つの特徴的な構造が存在することを認め、これらの構造が高水温域から低水温域へと向かい変態を開始するまでの接岸回遊過程と対応していることを示した。また、接岸回遊の最終段階で起こる稚魚への変態がどのような条件で開始するのか飼育実験により示した。その結果を実際のフィールドに適用することによって、餌生物との関係よりマアナゴ仔魚の回遊・成長戦略について考察した。さらに、仔魚の飼育実験により、体比重が成長にともなって増加することを示し、高水温域から低水温域へと向かう接岸回遊が仔魚の比重調整により行われている可能性を示した。 | |||||
| 言語 | ja | |||||
| 書誌情報 |
ja : 水産総合研究センター研究報告 en : Bulletin of Fisheries Research Agency 巻 24, p. 105-152, ページ数 48, 発行日 2008-03 |
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| 出版者 | ||||||
| 出版者 | 水産総合研究センター | |||||
| 言語 | ja | |||||
| ISSN | ||||||
| 収録物識別子タイプ | PISSN | |||||
| 収録物識別子 | 1346-9894 | |||||
| 書誌レコードID | ||||||
| 収録物識別子タイプ | NCID | |||||
| 収録物識別子 | AA11589591 | |||||
| 情報源 | ||||||
| 識別子タイプ | Local | |||||
| 関連識別子 | fra_k_24_105 | |||||
| 関連サイト | ||||||
| 識別子タイプ | URI | |||||
| 関連識別子 | https://agriknowledge.affrc.go.jp/RN/2010751357 | |||||
| 関連名称 | 日本農学文献記事索引（AgriKnowledge） | |||||
| 著者版フラグ | ||||||
| 出版タイプ | VoR | |||||
| 出版タイプResource | http://purl.org/coar/version/c_970fb48d4fbd8a85 | |||||
