| Project/Area Number |
10660174
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
General fisheries
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| Research Institution | The University of Tokyo |
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Principal Investigator |
MATSUDA Hiroyuki Ocean Research Institute, The University of Tokyo, Associate Professor, 海洋研究所, 助教授 (70190478)
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| Co-Investigator(Kenkyū-buntansha) |
TATSUKAWA Ken-ichi Ocean Research Institute, The University of Tokyo, Research Assistant, 海洋研究所, 助手 (20013584)
KATSUKAWA Toshio Ocean Research Institute, The University of Tokyo, Research Assistant, 海洋研究所, 助手 (90302679)
MATSUMIYA Yoshiharu Ocean Research Institute, The University of Tokyo, Professor, 海洋研究所, 教授 (10100885)
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| Project Period (FY) |
1998 – 2001
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| Project Status |
Completed (Fiscal Year 2001)
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| Budget Amount *help |
¥3,300,000 (Direct Cost: ¥3,300,000)
Fiscal Year 2001: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 2000: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 1999: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1998: ¥900,000 (Direct Cost: ¥900,000)
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| Keywords | stock fluctuation / risk assessment / strong year class / resource management / immature fish / Beyerton-Holt model / Beverton-Holt モデル / 繁殖価 / 収穫価 / 未定乗数法 / マサバ / マイワシ / 異形配偶 / 非協力ゲーム / 不確実性 / 漁獲量変動 / 順応管理 / 最犬法 / ベイズ法 / 絶滅の恐れ / 持続可能な漁業 / 生物多様性 |
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| Research Abstract |
Many fisheries have alternative target stocks and selectively exploit the one with the highest expected income. Although target switching is very common in practice, few attempts have thus far been made to study target switching. In this paper, we investigated the potential effects of target switching on the yield and sustainability of fish stocks. We simulated switching exploitation between two independent stocks, using a delay-difference model. Our study revealed that well-planned target switching increases yields and simultaneously decreases the risk of the stocks collapsing. Target switching decreases fishing pressure on the less abundant stock and helps the declined stock to recover. Therefore, the minimum stock level is increased by switching. As switching keeps both stocks at productive levels, the total yield is increased by switching. Target switching is effective, especially when the catchability increases with the depletion of a stock population. Target switching depends on the availability of information on stock abundance. Thus, we examined the vulnerability of switching to stock assessment errors. If the stock assessment is very uncertain, then little or no switching is recommended. Target switching can have substantial effects on fisheries. Therefore, we must investigate the mechanisms of switching and incorporate switching into management plans.
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