Report of the Working Group on Multispecies Assessment Methods (WGSAM). 10-14 October 2016 Reykjavik, Iceland

The Working Group on Multispecies Assessment Methods (WGSAM) met in Reykjavik, Iceland, 10–14 October 2016. In this tenth report of the pan-regional WGSAM, work fo-cused on four (B, E, F, G) of the multi-annual ToRs. Based on their knowledge, participants provided an updated inventory of progress of multispecies models in ICES Ecoregions (ToR A), noting those regions where no infor-mation was available. Reporting on ToR A was scarce compared to previous years, partly because recent relevant work was reported against ToR E and G instead. A Key Run (ToR B) of the Baltic Sea Ecopath with Ecosim (NS-EwE) model was present-ed and reviewed in detail by 4 WGSAM experts, and approved by the group following implementation of changes agreed in plenary at the meeting and verified by the 4 experts in January. The Key Run is documented in a detail in Annex 3, with key outputs summa-rised in Section 3 and data files made available on the WGSAM webpage). WGSAM also conducted an informal review of the LeMans modelling framework for potential applica-tion in the Irish Sea, and recommended adjustments to the framework for further review. Because the LeMans framework is a within-model ensemble addressing parameter uncer-tainty, this review also related to ToR D. Multispecies model skill assessment (ToR C) and multi-model ensemble methods (ToR D) were not emphasized this year. However, plans were made to coordinate future work for ToR C, and one ToR D presentation reviewed the utility of a dynamic multimodel ensemble for making inferences about the real world. This method can infer results for individual components of aggregate groups; the ensemble model uses correlations in other ecosystem models to determine what the models that group species would have predicted for individual species. A proof of concept for the North Sea was presented. Ecosystem indicator analyses (ToR E) were presented from a wide range of ecosystems. A theoretical analysis comparing results from the Celtic and North Seas with 4 “ideal-ized” fleets was presented to analyse the performance of selected indicators in a multi-species mixed fishery. Four indicators including the Large Fish Indicator (LFI) were examined, and shown to have mixed utility in measuring the impact of different fleet sectors, with the best indicator varying by ecosystem. A multivariate analysis of ecosys-tem responses to multiple drivers was conducted for four US ecosystems using gradient forest method to identify potential ecosystem thresholds. Other multivariate methods were reviewed that draw on the strengths of multiple indicators for the Northeast US shelf ecosystem. A food web based biodiversity indicator was presented with an applica-tion for the Baltic Sea. This could be extended to any ecosystem with an EwE or similar model. A community status indicator relating a species-area relationship to the LFI and mean trophic levels was presented for the Swedish west coast. Impacts of apex predators on fisheries (ToR F) were examined with one presentation and a group discussion planning further work. A multipecies production model was parame-terized to simulate interactions between three fish guilds, fisheries, and one marine mammal guild, concluding that fish reference points and trajectories change with marine mammal interactions. Fishery management was also important to reduce vessel interac-tions with and ensure prey supply to marine mammals