Is the estuary just a transit point for diadromous fish?: quantifying as a spawning ground

2023 Fiscal Year Final Research Report

• Project/Area Number: 22K20597
• Research Category: Grant-in-Aid for Research Activity Start-up
• Allocation Type: Multi-year Fund
• Review Section: 0603:Forestry and forest products science, applied aquatic science, and related fields
• Research Institution: Fisheries Research and Education Agency
• Principal Investigator: OTO Yumeki 国立研究開発法人水産研究・教育機構, 水産大学校, 助教 (30951488)
• Project Period (FY): 2022-08-31 – 2024-03-31
• Keywords: 通し回遊 / 汽水域 / ハゼ科 / 産卵回遊 / 個体群 / 繁殖生理 / 塩分適応

Outline of Final Research Achievements

This study investigated the importance of riverine estuaries as spawning grounds for diadromous species using goby fishes as a model. Key findings from field surveys and otolith microchemical analysis were that most adults of the target diadromous species migrated from freshwater areas to estuaries to spawn shortly before the spawning season, and that estuaries were used as spawning grounds at least as frequently as freshwater areas. In addition, the rearing experiment suggested that the testicular development of one of the target species was enhanced by their entry into brackish water environments. Another finding was that body size at the onset of reproduction was likely to differ depending on the availability of estuaries as growth habitats until breeding.

Free Research Field

水圏生態学

Academic Significance and Societal Importance of the Research Achievements

海と川を行き来する通し回遊種は，水産，学術のどちらにおいても重要である一方，生涯を通じて様々な水域を利用する必要があるため，昨今の環境改変から多大な負の影響を被っている．本研究では，野外調査や飼育実験が容易なハゼ科魚類をモデルに，良好な汽水環境の有無やそこへのアクセス性が，繁殖を通じて通し回遊種の個体群にインパクトを与えうることを示すことができた．商業的に重要な通し回遊種においても，汽水域で繁殖を行う，あるいは仔稚魚期に汽水域を利用する種は少なくなく，本研究の成果はそれらの種を保全する上でも有用な基盤情報になると期待される．