Carl O'Brien's scientific contributions

The Workshop on stock identification of West of Scotland cod (WK6aCodID) convened to recommend the most plausible scenario of population structure for stock assessment and fishery management advice. The review considered geographic variation and movements of cod lifestages inferred from genetic analyses, scientific surveys, fishery data, tagging, and otolith microchemistry and shape. Based on the review, several population structure scenarios were hypothesized (including the scenario assumed in the current advisory unit), and the plausibility of each scenario was evaluated. Practical implications of the most plausible scenario, including the derivation of a catch time-series, were considered to form recommendations for benchmark stock assessment workshops. The workshop considered three hypotheses - hypothesis 1: closed homogenous population; hypothesis 2: a metapopulation with overlapping subpopulations (but not necessarily with areas within Division 6.a) (Clyde, Dogger inshore, Dogger offshore) and hypothesis 3: multiple overlapping subpopulations related to Dogger stocks (between Division 4.a and Division 6.a) and a separate subpopulation of Clyde. While hypothesis 3 provides the strongest scientific evidence, treating the Clyde as a separate population is problematic with respect to reconstructing historical catches and undertaking assessments. Over the last two decades of local management with the Clyde cod closure, incorporating minimal catches into subpopulations is unlikely to impact assessments at the present time. Given the current weak state of Clyde cod, hypotheses 2 and 3 would be practically indistinguishable in terms of assessment outcome and the workshop considers hypothesis 2 amenable to stock assessment in the short- to medium-term, while investigations continue into the assessment of the Clyde cod and the improvement of data availability. Given linkages of the inshore and offshore subpopulations to cod in Division 4.a, it is recommended to combine the North Sea and West of Scotland cod assessments in a future benchmark. The workshop elaborated two scenarios with respect to a potential ICES data submission consistent with the modelling approaches being considered for the North Sea cod stock (cod in Subarea 4, Division 7.d and Subdivision 20); namely, either that data are submitted for the whole of Division 6.a as for the current ICES stock assessment, or that data are split into stock components as defined under hypothesis 2 (and hypothesis 3). In these cases, the workshop suggested that two approaches be considered based on data availability and a conversation between ICES national data submitters and ICES stock assessors. ICES data submitters and ICES stock assessors should agree on a suitable time period for data splitting; considering the current assessment time-series for both West of Scotland and North Sea stocks and data quality back in time. Having addressed its Terms of Reference, the workshop noted that there is potential for much reshaping of Atlantic cod stock assessments currently. With the four primary cod assessments (Celtic Sea, Irish Sea, West of Scotland and North Sea) presently exhibiting issues. Primarily these revolve around continued low catch tonnage, which translates into low catch numbers-at-age and resolves with heightened uncertainties in assessments. To investigate and review further, the workshop proposes that a planned approach be developed within ICES, through initial roadmapping for improving assessments and the basis for advice.

The Workshop on the Development of Quantitative Assessment Methodologies based on Life-history traits, exploitation characteristics, and other relevant parameters for data-limited stocks (WKLIFE) focuses on the provision of sound advice rules for data-limited stock (DLS) assess-ments that are within the ICES MSY framework. This ninth workshop was convened to further address the challenges to the evidence base for the provision of ICES advice with specific refer-ence to DLS. The reviewers’ report of WKLIFE VIII (ICES, 2018) was used as the basis to draft ICES technical guidance on advice rules for stocks in Categories 3 and 4 following the meeting in 2018. The draft document reflected the conclusions of the WKLIFE VIII meeting report but in order to provide a good guidance document to the ICES community, some of the text and steps identified required further elaboration. The intersessional work undertaken ahead of this WKLIFE IX meeting provided a basis to revise the draft and during this WKLIFE IX meeting, the draft technical guidance was revised and updated. The draft report of, and recommendations from, the ICES workshop on data-limited stocks of short-lived species (WKDLSSLS) was re-viewed and additional simulation studies undertaken during WKLIFE IX, and the need for spe-cific advice rules for these stocks examined. Annex 3 to this report contains the revised and agreed text by the participants at WKLIFE IX. Specifically, the draft ICES technical guidance was revised and amended based on the work presented at WKLIFE IX and its previous workshops with respect to short-term forecasts utilising a surplus production model (SPiCT – Stochastic Production model in Continuous Time), and harvest control rules for length-based approaches, for short-lived species, and for bycatch elasmobranch stocks.

The Workshop on the Development of Quantitative Assessment Methodologies based on Life-history traits, exploitation characteristics, and other relevant parameters for stocks in categories 3–6 (WKLIFE VIII), chaired by Carl O'Brien (UK) and Manuela Azevedo (Portugal) met in Lisbon, Portugal, 8–12 October 2018, to further develop methods for stock assessment and catch advice for stocks in categories 3–6, focusing on the provision of sound advice rules that are within the ICES MSY framework.

The Workshop on the Development of Quantitative Assessment Methodologies based on Life-history traits, exploitation characteristics, and other relevant parameters for stocks in categories 3-6 (WKLIFE VII), chaired by Carl O'Brien (UK) and Manuela Azevedo (Portugal) met in Lisbon, Portugal, 2–6 October 2017, to further develop methods for stock assessment and catch advice for stocks in categories 3–6, focusing on the provision of sound advice rules.

This poster shows how a multispecies and mixed fisheries model can be tuned to provide a simultaneous forecast of many fish stocks. These forecasts are then validated by means of a hindcast evaluation for the period 2010-2015. Results are presented which show that the model is potentially useful for making management decisions.