WKREBUILD_2020.pdf (2.24 MB)
Workshop on guidelines and methods for the evaluation of rebuilding plans 2020 report
reportposted on 2020-01-01, 00:00 authored by ICESICES
The Workshop on guidelines and methods for the evaluation of rebuilding plans (WKREBUILD) chaired by Vanessa Trijoulet (Denmark) and Martin Pastoors (Netherlands) met from 24 to 28 February 2020. The workshop attracted 27 participants from the US, Canada, Europe and FAO.When stocks are estimated to be below Blim1 and there is no perceived possibility of rebuilding above Blim within the time-frame of a short-term forecast, ICES has regularly recommended zero catch in combination with the development of a rebuilding plan.A review was carried out on the international experience on the development, evaluation and implementation of rebuilding plans for fisheries management in the Northeast Atlantic and in other fora around the world. In the Northeast Atlantic, rebuilding plans have been implement-ed in the past (e.g. the cod recovery plans of the early 2000s) but ICES has played a limited role in evaluating the performance of such recovery plans and does not have the tools or criteria to evaluate such plans. Recently, when a rebuilding plan for herring in 6.a 7.bc was submitted to ICES for evaluation, ICES refrained from providing such an evaluation. In the US and Canadi-an approaches, the legal framework determines the triggering and required elements of re-building plans. Such a legal imperative does not exist in the Northeast Atlantic. Nevertheless, the US and Canadian experiences provided useful elements that could be included in establish-ing ICES approach to rebuilding plans.Several case studies were presented on potential tools for the evaluation of rebuilding plans. Particular attention was given to evaluating options for harvest control rule options of such a plan. The tools focused mostly on short to medium term explorations of the probability of achieving a rebuilding of stocks. Because rebuilding plan evaluations need to be ready and available at short-notice when required, it was concluded that relatively standardized tools (i.e. packages or compiled code) to carry out such evaluations would be preferable over custom-made evaluation tools. In addition, certain modelling considerations were highlighted as im-portant such as realistic assumptions of productivity, uncertainty, bias in assessments and im-plementation error and the possibility of estimating the probability of achieving a rebuilding of stocks.Criteria for the acceptability of rebuilding plans will require an agreed Limit Reference Point (LRP) for initiating a rebuilding plan, definition of targets for fishing mortality or stock bio-mass, time-frames and the acceptable probabilities whether the rebuilding targets have been achieved. All of these should take into account realistic levels of uncertainty and being con-sistent with international best (scientific) practices. Although it was recognized that Blim would be the most likely candidate LRP triggering a rebuilding plan, the current approach in ICES for the determination of Blim was questioned during the workshop because it requires a more or less subjective classification of the stock-recruitment pairs into different types. In other re-gions, the LRP is often set as a certain proportion of the SSB at maximum sustainable yield (BMSY), e.g. 40% BMSY. If changes in productivity have been experienced in recent years at these are taken into account when estimating MSY reference points, the proportion of BMSY approach would likely lead to greater changes in the estimated value of LRP than the current ICES pro-cedures used to estimate Blim, which rely on stock-recruitment pairs or definition of the lowest observed biomass (Bloss). This could have a large impact on the rebuilding target for stocks that experience changes in productivity regimes.
Published under the auspices of the following ICES Steering Group or Committee