Study on current velocity so as not to cause oxygen debt targeted for conserving and restoring the fish population in paddy fields

2023 Fiscal Year Final Research Report

• Project/Area Number: 19K06302
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 41030:Rural environmental engineering and planning-related
• Research Institution: National Agriculture and Food Research Organization
• Principal Investigator: Takemura Takeshi 国立研究開発法人農業・食品産業技術総合研究機構, 農村工学研究部門, グループ長補佐 (20373227)
• Project Period (FY): 2019-04-01 – 2024-03-31
• Keywords: 水田域魚類 / タモロコ / 酸素消費量 / 臨界遊泳速度 / 回復

Outline of Final Research Achievements

To conserve and restore the fish population in paddy fields, a 2-stage experiment was conducted to seek the range of current velocity so as not to cause oxygen debt. In the 1st-stage experiment, Ucrit: critical swimming speed, was sought. In the second stage, the current speed was gradually increased to three different upper limits based on the Ucrit. After reaching these upper limits, the shift in oxygen consumption was analyzed under slow current velocity (0.8BL/s). As a result, it was suggested that the range of current velocity not to cause oxygen debt was under about 3.4BL/s, under the water temperature condition of 21 degrees Celsius.

Free Research Field

水田生態工学

Academic Significance and Societal Importance of the Research Achievements

長時間にわたり遊泳可能な速度域，とくに休憩可能な速度域は見過ごされがちであった．本研究では，夏季を想定した水温条件の下，遊泳中から遊泳後にかけた酸素消費量，とくに遊泳後の緩流速下でみられる酸素消費量の推移に着目し，緩流速とした直後の急落かつ低位安定と，高位からの漸減という差が3.38・3.82BL/sの間で生じたことを確認した．このことから酸素債を発生させない，すなわち長時間にわたる遊泳や休憩可能な速度域は安全側を見込めばおよそ3.4BL/s程度迄の範囲と推察され，水田域魚類の保全・再生に向けて重要な知見となることが期待される．