The ecology of Japanese eels in a freshwater habitat

2019 Fiscal Year Final Research Report

• Project/Area Number: 17K07921
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Aquatic bioproduction science
• Research Institution: Kindai University
• Principal Investigator: WATANABE Shun 近畿大学, 農学部, 准教授 (60401296)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Keywords: ニホンウナギ / 黄ウナギ / 養殖ウナギ / 放流 / 肥満度 / 水温 / 行動 / 固執性

Outline of Final Research Achievements

Daily and seasonal behavior of Japanese eels, Anguilla japonica, were analyzed using acoustic biotelemetry within a semi-natural experimental pond in Miyazaki Prefecture, and field surveys were conducted in 3 small rivers in Shizuoka Prefecture in order to evaluate their ecology in freshwater habitats. Yellow eels, elvers and glass eels were mainly active from spring to summer when the water temperature was rising and when they had higher growth and condition factor. Each eel in the semi-natural experimental pond displayed various distinctive spatial and temporal individual behaviors among different months. The spring to summer growth period, behavioral individuality, and competitive interactions are likely ecological characteristics of Japanese eels. Differences in density, body size and sex ratio were also found between 2 of the small rivers. These observations show the ecological plasticity of Japanese eels that are caused by the river environments and competition among individuals.

Free Research Field

魚類生態学

Academic Significance and Societal Importance of the Research Achievements

黄ウナギの生態学的研究のみならず、その成果を踏まえ、河川環境の修復や改善を視野に入れたことは初の試みである。本研究から得られた成果は本種のみならず、水圏生物、特に海と川を行き来する通し回遊性生物の保全、持続的利用、資源管理に関する研究の好モデルとなると考える。また、本研究で得られた成果を学生、消費者および一般市民へ伝えるボトムアップの保全活動は教育的・啓発的な意義を持つ。