WKMFOA explored the benefits and challenges of adopting multiannual assessments for fisher-ies management. The primary objective of a multiannual assessment approach is to reduce the frequency of full stock assessments. This saves expert time, though the costs associated with data collection and handling are unchanged. Multiannual assessments provide opportunities for more in-depth analysis, expansion of advice across additional stocks and ecosystem components, and allocation of time to fundamental science rather than routine assessments.
The workshop focused on evaluating the precautionary nature of multiannual advice. Building upon previous ICES work (WKFREQ), it investigated whether multiannual advice could remain scientifically robust. One key aspect discussed was the need for intermediate-year checks to ad-dress the limitations inherent in stock assessment models. These checks, based on simple, prede-fined indicators, follow a "traffic light" system that can trigger a reassessment according to ICES protocols. Specifically, the reopening protocol considers catch data, commercial CPUE data, in-dices of recruitment and other relevant age classes, and observed data comparisons against pro-jections from recent assessments, with predefined trigger indices signalling a need for mid-term advice updates.
WKMFOA recommends that the frequency of full stock assessments be determined during the benchmark process. Variability in data availability across stocks—such as catch data, logbook entries, and survey information—necessitates a tailored approach for each assessment. In re-viewing ACOM’s initial criteria for multiannual advice, WKMFOA suggests simplifying the cri-teria. One criterion suggests that biased assessments (based on Mohn’s rho) should be excluded from multiannual assessment. However, unreliable stock assessments do not become more ac-curate by repeating the assessment more frequently and a more appropriate action is to improve the quality of the assessment during the benchmark. Given the broadly applicable simulation evaluation tool that has been developed, simple simulation analyses can be easily performed. There is therefore no need to explicitly exclude a stock for multiannual consideration based on the current exploitation pressure and the status of the stock. However, two criteria for excluding stocks from multiannual assessment remain i.e. short-lived species with variable recruitment and stocks with zero catch advice for three or more consecutive years. Heavily depleted stocks that had zero advice but for less than the last 3 consecutive years may be candidates for multiannual simulation evaluation.
This workshop examined specific stocks through simulation, including Central Baltic Herring, Gulf of Herring, Southern Hake, Southern White Anglerfish, Bay of Biscay Sole and megrim in the Cantabrian Sea and Atlantic Iberian waters. Additional working documents for two Nephrops and one plaice stock applied a more qualitative examination.
WKMFOA emphasizes the need for continued improvements to stock assessment databases and models, aiming for enhanced reliability in multiannual advice through further simulation anal-yses.