Mechanism of timing of downstream migration for Japanese eels

2022 Fiscal Year Final Research Report

• Project/Area Number: 18K14510
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 40030:Aquatic bioproduction science-related
• Research Institution: The University of Tokyo (2021-2022); Kobe University (2018-2020)
• Principal Investigator: Itakura Hikaru 東京大学, 大気海洋研究所, 助教 (40749040)
• Project Period (FY): 2018-04-01 – 2023-03-31
• Keywords: 回遊開始機構 / ニホンウナギ / 春機発動 / 標識再捕 / 耳石成長解析

Outline of Final Research Achievements

The objective of this study was to establish a method to predict the onset of downstream migration of Japanese eels at the individual level in summer, and to clarify the process of decision-making mechanisms related to the onset of the migration of eels. Using mark-recapture experiment of female Japanese eels in an artificial pond, it was found that the diameter of egg of puberty individuals was significantly larger than that of non-puberty individuals in fall, indicating that the onset of migration of eels in fall is predictable at the individual level during summer. In addition, growth analysis of eels collected in Lake Jinzei, Shimane Prefecture, revealed that individuals having high growth pattern start their migration at younger age than low growth pattern individuals.

Free Research Field

魚類生態学

Academic Significance and Societal Importance of the Research Achievements

本研究の実施により、これまで困難であった秋季におけるウナギ属魚類の銀化/回遊開始予測について、夏季に卵径を測定して春機発動の有無を調べることで、秋季の銀化/回遊開始を事前に個体レベルで予測することが可能となった。これにより、黄ウナギをその年に銀化/回遊開始個体か残留個体かに判別することで両者の成長パターンなどの比較から、ウナギ属魚類の回遊開始に関わる意思決定機構の解明が可能となるため学術的意義は高い。また、事前の銀化/回遊開始の予測は銀ウナギの確保を可能とするため、社会的意義も高いものと判断できる。