How big are footprints of fly dragging seines? Swept area estimation

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K06185
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 40030:Aquatic bioproduction science-related
• Research Institution: Nagasaki University
• Principal Investigator: Matsushita Yoshiki 長崎大学, 水産・環境科学総合研究科(水産), 教授 (30372072)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: 底びき網漁業 / Trawl footprint / 漁業の環境への影響 / かけまわし漁法 / ごち網漁法

Outline of Final Research Achievements

Trawl footprints were determined using various measurement techniques for the several fly dragging fisheries (Kakemawashi and Gochiami), in which the gear shape and speed of movement changes from moment to moment. Trawl footprints of these fisheries were much larger than those estimated for other Japanese towed net fisheries using vessels and nets of similar size. Although fly dragging fisheries are considered to be ecosystem-friendly because light and small fishing gear are used, the large trawl footprint estimated in this study may have a negative impact on the seafloor environment because it shears off sessile organisms, seaweeds and/or sea grasses on the seafloor and flattens the seafloor.

Free Research Field

漁業生産工学

Academic Significance and Societal Importance of the Research Achievements

底びき網漁業が影響する海底の範囲は「Trawl footprint」と呼ばれ，この範囲内の海底は漁具の通過によって物理的な作用を受け，そこに生息する生物や植物はその影響を受けることとなる。Trawl footprintは漁業の海底生態系への悪影響を検討する上での重要なエビデンスであり，海洋保護区や禁漁区の設定検討の有用な資料でもあるが，開口装置を用いない「かけまわし」や「ごち網」では，漁具の形状と動きが刻一刻と変化するため， Trawl footprint の推定が難しい。水中計測技術を組み合わせて，かけまわし漁具とごち網漁具が海底を掃過する範囲を調べた。