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- ItemOpen AccessRefinements of the BR CMP as of April 2022(2022) Butterworth, Douglas; Rademeyer, RebeccaThe BR CMP is adjusted in a few respects, most importantly by allowing limited temporal dependence in the values of the control parameters over the first few years of management, to allow for smoother transitions in the TACs from 2022 to 2023. This was necessitated especially by the now higher West area TAC for 2022 included in the updated package. Results are provided for the four basic development tunings, plus one variant for one of those tunings where the default maximum TAC decrease constraint is reduced from 30% to 20%. Suggestions are made of areas for possible improvement in performance, which would require some further refinements of this CMP.
- ItemRestrictedOn the development of a roadmap for new formal harvest strategies for SIOFA(2022) Butterworth, DouglasThe Consultants past experience with conducting assessments of and/or providing management advice for SIOFA fish stocks has indicated that a key problem has been the lack of background information on the data available and how they relate to the way the fishery operates. That missing information is a key input to the assessment process, and its ability to provide reliable results. The International Whaling Commission’s “harvest strategy roadmap” is reviewed. Their first step for any stock of a “pre-assessment” process to compile the data to be used in the harvest strategy analyses and how they should be interpreted, is suggested to be an essential component of any similar SIOFA roadmap. This process should be put into practice by the appointment, for any stock for which a harvest strategy is to be developed, of a Technical Sub-Committee which would meet separately from the SIOFA Scientific Committee and report back to it. This Sub-Committee would include persons with the relevant expertise about the stock to provide this missing information and to develop ToR’s for the basis on which the harvest strategy development should proceed. Overview comments are provided about the process that would then follow. An important decision to be made is whether the harvest strategy for a specific stock is to be based on the “best assessment plus harvest control rule” approach or on Management Strategy Evaluation (MSE). A table is provided summarising the details associated with this “Technical Sub-Committee” pre-assessment component of a harvest strategy development roadmap.
- ItemOpen AccessEffect of missing values from the Canadian spring and fall surveys of NAFO Divisions 3LNO on the calculation of the TAC using the Greenland halibut HCR(2022) Regular, P M; Butterworth, Douglas; Rademeyer, RebeccaTo test the impact of ignoring recent missing abundance indices for Greenland Halibut in NAFO divisions 2+3KLMNO on applying the accepted HCR for this population to provide a TAC recommendation for 2023, the impact of similar exclusions in the past is examined and found to be small. To further test of the impact of the missing 2021 index from the Canada Fall 3LNO survey, a range of pessimistic to optimistic abundance index values were assumed to assess the plausible range of impact this one value might have on the TAC computation. The range of the resultant TACs is small, and the difference of the impact of TACs at either end of this range on exploitable biomass projections for the next year is found to be negligible. Hence, it is argued, the minimalist and straightforward approach of simply ignoring the missing 2021 Canadian Fall 3LNO result in the four-survey version of the HCR agreed last year would be a defensible and appropriate approach to the required adjustment of the implementation of this HCR to provide a TAC recommendation for 2023.
- ItemMetadata onlyUpdate of the proposed model framework to form the basis for immediate future assessments of the South African hake resource. BENEFIT/NRF/BCMLE December 2004 Stock Assessment Workshop document(MARAM, 2004) Rademeyer, R A; Butterworth, D SUpdate of the proposed model framework to form the basis for immediate future assessments of the South African hake resource. BENEFIT/NRF/BCMLE December 2004 Stock Assessment Workshop document
- ItemRestrictedA case for a higher critical biomass threshold in the anchovy‐only OMP‐ 18rev than in OMP‐18(2021) de Moor, Carrynde Moor (2021a,b) has provided a number of results for alternative candidate Management Procedures for an anchovy‐only OMP‐18rev. The SWG‐PEL TTG has suggested that the shape of the anchovy HCR should remain the same as that for OMP‐18 (de Moor 2018a) ...