Workshop on Unavoidable Survey Effort Reduction 2 (WKUSER2).

The Working Group on Multispecies Assessment Methods (WGSAM) aims to advance the operational use of knowledge on predator-prey interactions for advice on fisheries and ecosystem management. This report presents an update of the multispecies SMS keyrun model for the Baltic Sea including its review by the working group, and the review of three modelling frameworks for the Georges Bank marine ecosystem. The Baltic Sea keyrun provides updated estimates of cod predation mortality for the Baltic Sea sprat and central Baltic herring stocks. The model integrates fishery and survey data on the two clupeids and makes extensive use of the cod stomach data (i.e. 64 000 stomachs are used as input to the model). Estimations of predation mortality are consistent with previous estimates and suitable for inclusion in the stock assessment of the two clupeid stocks. Predation remains low on all ages for both herring and sprat as a result of the low cod stock size. The large modelling framework for the Georges Bank comprises a multispecies production model, a multispecies length-based model and a mass-balanced ecosystem model. While none of the three models was at that stage to be evaluated as a keyrun, with further development they could complementarily and in conjunction contribute to the EBFM of the Georges Bank