Assessment model development and management strategy evaluation for fisheries stocks under regime shifts

2021 Fiscal Year Final Research Report

• Project/Area Number: 19K15905
• 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: Fisheries Research and Education Agency
• Principal Investigator: Nishijima Shota 国立研究開発法人水産研究・教育機構, 水産資源研究所(横浜), 研究員 (50805116)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: レジームシフト / 水産資源 / 状態空間モデル / 隠れマルコフモデル / 生物学的管理戦略評価 / 最大持続可能生産量 / 管理基準値 / 密度効果

Outline of Final Research Achievements

I addressed the improvement of stock assessment and the evaluation of management strategies for fishery resources that may exhibit regime shifts. By developing a simulation model for the Pacific stock of chub mackerel, I found that a state-space stock assessment model estimated parameters more accurately than the stock assessment model used currently in Japan. I then developed a framework that included a post-recruitment density dependence in individual growth and maturation in biological reference points and found that including the post-recruitment density dependence enabled an efficient exploitation of the Pacific stock of chub mackerel. I also developed a state-space stock assessment model for Japanese flying squid, finding that recruitment regime shifts occurred in this species. In addition, I worked on the detection of regime shifts using a hidden Markov model for 32 fish stocks in Japan.

Free Research Field

水産資源学

Academic Significance and Societal Importance of the Research Achievements

水産資源評価モデルの改良のため、状態空間資源評価モデルの開発や改善に取り組み、信頼性の高い生物学的許容漁獲量の算出が可能になった。状態空間モデルや隠れマルコフモデルといった高度な統計モデルによるレジームシフトの検出に取り組み、我が国資源の加入量変動メカニズムの理解の一助となった。加入後の成長や成熟率の密度効果を管理基準値の計算に含めるという考えは国際的に見ても新しい取り組みであり、これにより効率的な漁獲が可能になることが示唆された。本課題で開発した加入後の密度効果を管理基準値計算に組み込む手法は、資源評価のデータと結果に基づいており、水産業の持続性と水産資源の持続的利用に貢献しうる成果である。