Comparison of spawning and seaward-migration ecology of chum salmon (Oncorhynchus keta) in different water temperature

2023 Fiscal Year Final Research Report

• Project/Area Number: 20K06202
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 40030:Aquatic bioproduction science-related
• Research Institution: The University of Tokyo
• Principal Investigator: Aoyama Jun 東京大学, 大気海洋研究所, 教授 (30343099)
• Project Period (FY): 2020-04-01 – 2024-03-31
• Keywords: サケ / 三陸沿岸河川 / 繁殖生態 / 産卵床

Outline of Final Research Achievements

Environmental preferences of wild chum salomon (Oncorynchus keta) to make their spwaning reds were studied in the Kozuchi River in Otsuchi Town and the Unosumi River in Kamaishi City, Iwate Prefecture, Japan. In the Unosumi River where groundwater upwelling is relatively low, the water temperature during the salmon spawning season from October to January ranged from 1.0 to 14.0°C, while the Kozuchi River, which has abundant groundwater upwelling was significantly warmer ranging from 4.6 to 15.8°C. Distribution of the spawning redds was found to be concentrated near upwellings in the Unosumai River, whereas the vicinity of upwelling was avoided in the Kozuchi River. It likely to be due the fact that salmon select areas near upwelling to obtain appropriate water temperatures under low water temperatures, whereas they avoid anoxic conditions caused by upwelling goundwater in environments where adequate water temperature is available.

Free Research Field

魚類生態学

Academic Significance and Societal Importance of the Research Achievements

年間18億匹程度の稚魚を放流してきたにもかかわらず、我が国沿岸のサケ漁獲量は大きく増減を繰り返し、2000年頃からは顕著な減少傾向を示している。近年では人工孵化放流事業の弊害が指摘され、天然環境で産卵するサケ野生魚の重要性が指摘されている。三陸沿岸河川におけるサケ野生魚の実態は明らかでなく、生態学的情報の蓄積が急務である。本研究では、三陸沿岸河川におけるサケ自然産卵の時期や量などの基礎情報に加え、産卵場所選択にかかる環境条件について一定の知見を得ることができた。地球温暖化に伴い、三陸におけるサケ回帰資源は危機的に減少しているが、海洋だけでなく、河川環境も含めた管理・保全方策は不可欠である。