Browsing by Subject "empirical management procedures"

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    Complex assessments or simple management procedures for efficient fisheries management: a comparative study
    (Oxford University Press, 2015) Geromont, Helena F; Butterworth, Doug S
    Complex stock assessment methods are data- and expertise-hungry, with the annual updates of catch-at-age data and models typically seen as an essential requirement for sound management. But are the heavy commitments of resources required for this level of annual intervention really necessary to achieve efficient long-term fishery management? This question is addressed through a retrospective analysis of management performance over the last 20 years for four North Atlantic fish stocks. The assessments for two of these stocks have exhibited fairly strong retrospective patterns. The actual assessment advice for these stocks was provided based on complex assessment methods making use of age data. The outcomes are compared with what could have been achieved with much simpler catch control rules based upon age-aggregated survey indices alone. Even for the stocks whose assessments exhibit retrospective patterns, these simple rules can achieve virtually equivalent catch and risk performance, with much less interannual TAC variability, compared with what actually occurred over the past 20 years.
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    Exploration of empirical management procedures based on longline CPUE index and aerial survey index
    (2010) Kurota, Hiroyuki; Fujioka, Ko; Sakai, Osamu; Butterworth, Doug S
    We evaluated performance of four Management Procedures (MPs) with empirical algorithms to determine TACs using information from the longline CPUE series and the aerial survey index. This MP exercise shows that TAC levels in the future are quite different depending on six management targets (tuning levels for spawning biomass recovery) that were proposed by the commissioners in April 2010. It also indicates that MPs with larger TAC reduction in the early years, which might not be preferred from a socio-economic viewpoint, enable quicker stock rebuilding and greater TAC increases in later years, even though they achieve the same long-term management target for spawning biomass recovery.
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    Further evaluation of empirical management procedures based on longline CPUE index and aerial survey index
    (2010) Kurota, Hiroyuki; Fujioka, Ko; Sakai, Osamu; Takahashi, Norio; Butterworth, Doug S
    Based on recommendations made during the third Operating Model and Management Procedure Technical Meeting (June 2010, Seattle), we have revised and evaluated “HK” Management Procedures (MPs) using empirical algorithms to determine TACs using information from the longline CPUE series and the aerial survey (AS) index. The exploration of HK variants showed that this MP can behave in a variety of ways as its control parameters and sub-algorithms are changed. As evident also from previous trials, MPs with larger TAC reduction in the early years, which might not be preferred from a socio-economic viewpoint, enable quicker stock rebuilding and greater TAC increases in later years, while still achieving the same long-term management target for spawning biomass recovery (though this comparison is complicated by transient effects).