Report of the Inter-Benchmark Protocol on Baltic Salmon (IBPSalmon)

The Inter-Benchmark Protocol for Baltic Salmon [IBPSalmon] (Chair: Johan Dannewitz, Sweden) met by correspondence between May and December 2012. The work was carried out by members of the Assessment Working Group on Baltic Salm-on and Sea Trout (WGBAST) and two external reviewers, with support from ICES Headquarters, comprising a total of 17 persons.

The main objective of the IBP was to improve parts of the assessment model used for Baltic salmon, and produce a Stock Annex to be implemented in 2013 assessment work. The prioritized issues handled during the IBP had earlier been discussed and agreed upon at the WGBAST meeting in 2012. Outcomes of the IBP include 1) inclu-sion in the assessment model of additional data on survival at sea of reared salmon, which is assumed to increase precision in estimates of relative abundance of wild and reared salmon, 2) updated correction factors for discard proportions, and for un-derreporting of tag recaptures, catches and fishing effort, and 3) an updated assess-ment model where maturation rate is allowed to vary over time due to e.g. climate variation, which is assumed to improve estimates of salmon survival and abundance at sea.

A few additional issues; inclusion of ecosystem data to improve salmon survival es-timates and stock projections, inclusion of southeastern rivers stocks in the full as-sessment model, and an update of the hierarchical stock–recruit model were also handled but for different reasons the work could not be finalized during the IBP. For these issues, recommendations on progress to be made and identification of data needs are presented.