Permeability of dam reservoirs for stream fishes and population variability in isolated tributaries

Research Project

Project/Area Number	18K18226
Research Category	Grant-in-Aid for Early-Career Scientists
Allocation Type	Multi-year Fund
Review Section	Basic Section 64040:Social-ecological systems-related
Research Institution	Public Works Research Institute
Principal Investigator	SUEYOSHI Masanao 国立研究開発法人土木研究所, 土木研究所(つくば中央研究所), 専門研究員 (70792927)
Project Period (FY)	2018-04-01 – 2022-03-31
Project Status	Completed (Fiscal Year 2021)
Budget Amount *help	¥3,770,000 (Direct Cost: ¥2,900,000、Indirect Cost: ¥870,000) Fiscal Year 2020: ¥520,000 (Direct Cost: ¥400,000、Indirect Cost: ¥120,000) Fiscal Year 2019: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000) Fiscal Year 2018: ¥1,950,000 (Direct Cost: ¥1,500,000、Indirect Cost: ¥450,000)
Keywords	分断化 / 生息地 / 淡水魚 / 人為影響 / 生態系管理 / ダム湖 / 魚類 / 個体群 / 次世代シーケンサー / 集団遺伝 / 生息域サイズ / 孤立 / 集団遺伝学 / ダム / 個体群存続 / 河川
Outline of Final Research Achievements	Dam impoundment is unsuitable habitat for lotic organisms and may disrupt individual movements among tributaries flowing into the impoundment. In this study, we examined fish assemblages in the tributaries that flowed into each of the lentic dam impoundments and the lotic mainstream to verify whether the dam impoundment impedes the migration of riverine fish species. The species richness of fish assemblages in the tributaries of the dam impoundment was lower than that in the flowing river. The reduction was larger as the tributaries became smaller. Genetic analysis indicated that the populations in the tributaries of the dammed impoundment were more genetically differentiated than those in the flowing rivers. In conclusion, dammed impoundments would impede the movement of riverine fishes and cause the extinction of local populations in the tributaries.
Academic Significance and Societal Importance of the Research Achievements	近年、老朽化したダムの補強や激化する気候変動に対応するため、全国各地のダムで再開発事業が進められている。再開発では、主に貯水容量が増やされる傾向にあるため、ダム湖が河川生物に及ぼす影響をを明らかにすることで、再開発時の影響を正しく評価し、緩和策の検討が可能となる。本研究の成果は、ダム湖という表面上は水でつながっている環境が流水を好む河川性魚類の移動を阻害していることを示唆した。