Working Group on Multispecies Assessment Methods (WGSAM; outputs from 2023 meeting)

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. Key runs of multispecies and ecosystem models provided by WGSAM are integral to this mission. They serve as a robust component of ecosystem science that seamlessly integrates into the ICES advice.

This report presents an update of the multispecies SMS key-run model for the North Sea and its review by the working group based on established review criteria. The updated model extends to input time-series to 2022 and includes a more extensive revision of the time-series of marine birds and grey seal population numbers. Additional improvements of this key-run include (i) one extra year of grey seal diet data (i.e., 1985, 2002, 2010); (ii) plaice is now a prey species, although predation is at the moment limited to grey seal; (iii) improved compilation of fish diet data including estimation of variance of the estimated prey proportions. WGSAM recommends the use of natural mortality estimates from the North Sea SMS key-run for use in single species stock assessment models of North Sea haddock, herring, Norway pout, sandeel (estimates are disaggregated for the southern and northern North Sea), sprat, and whiting. The SMS key-run continues to assume a single North Sea cod stock in contrast to the recent split into three components which makes assimilation of the natural mortality estimates into the new cod assessments problematic. More work is needed to harmonise the new fish stomachs with the old ones before they could be integrated in the North Sea key-run.