Population dynamics of salmonid fishes: factors affecting the variation in population fluctuation

2018 Fiscal Year Final Research Report

• Project/Area Number: 25450293
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Aquatic bioproduction science
• Research Institution: Fisheries Research and Education Agency
• Principal Investigator: Kentaro Morita 国立研究開発法人水産研究・教育機構, 北海道区水産研究所, 主任研究員 (30373468)
• Co-Investigator(Kenkyū-buntansha): 坪井 潤一 国立研究開発法人水産研究・教育機構, 中央水産研究所, 主任研究員 (80524694)
• Project Period (FY): 2013-04-01 – 2019-03-31
• Keywords: サケ科魚類 / 個体群動態

Outline of Final Research Achievements

Early life is believed to be a critical stage for determining survivorship in all fish. Many studies have suggested that environmental conditions in the ocean determine the total survival rate of Pacific salmon, however, we found that the variation in survivorship of chum salmon was explained by river environmental conditions. In additions, survival rates of hatchery-reared chum salmon was positively correlated with the length (in days) of the fry out-migration period with temperatures suitable for migration. Recent studies have suggested that hatchery releases may exert negative effects on wild salmon productions. However, it is unclear whether the salmon population would persist without hatchery supplementation. We proposed a management procedure for determining the stocking efforts of salmon fry with a feedback control loop to reduce the risk of population decline.

Free Research Field

魚類生態学

Academic Significance and Societal Importance of the Research Achievements

地球温暖化は、単に平均気温が高まるというだけではなく、集中豪雨や竜巻などの異常気象の頻度が増したり、季節の移り変わりのパターンにも変化をもたらすことが懸念されている。例えば、春が短くなる、すなわち、冬が終わるとすぐに夏がやってくるという“二季化”という言葉も最近では聞かれるようになった。本研究では、汎用性のある二季化の強さを示す指標を開発し、ある時期の平均温度だけではなく、季節の移り変わりのパターンについても着目する必要性をアピールした。また、外来種の増加、河川工作物による分断化、種苗放流がサケ科魚類の個体数変動に及ぼす効果に関する知見も蓄積することができた。