Benchmark Workshop of Greater silver smelt

Greater silver smelt (Argentina silus) stocks assessed by ICES (aru.27.123a4, aru.27.5a14, andaru.27.5b6a, and aru.27.6b7–1012) have never gone through a full benchmark proceeding. The first three of these stocks, located respectively in the waters surrounding Norway and northern Europe, Iceland and Greenland, and the Faroe Islands, currently have directed fisheries and areassessed using a category 3 framework. Greater silver smelt stocks in Icelandic and Greenlandicwaters (aru.27.5a14) and the Faroe Islands (aru.27.5b6a) however, likely have enough qualitydata to upgrade the assessments to a category 1 framework. The purpose of this benchmark proceedingis to evaluate potential category 1 assessments of these two stocks and a category 3 assessmentof the stock in Norwegian and northern European waters (aru.27.123a4).

This process began with exploratory assessments being presented at WGDEEP in 2019, was followedby a data evaluation workshop that was held in Reykjavík, Iceland in November 2019 tocompile data for analyses of stock structure and compare possible assessment methods, and wasfinalized with a benchmark meeting in February 2020 and a series of follow-up WebEx meetings.The largest challenges found in achieving category 1 assessments for this species included 1) compiling enough data from various sources to cover the full range of the species, 2) producing reliable age–length key generation methods, and 3) dealing with high interannual variability insurvey indices.

It was also determined that biological or genetic patterns generally support the stock divisionsas they are set currently; not enough evidence was available to support a change in these boundaries.

For the category 3 stock aru.123a4 three indices were examined in SPiCT, and combination ofthose, of which two had been recalculated. The data were found still to be too limited to recommenda SPiCT assessment to provide reference points in advice for the stock at this point. However,the output from SPiCT can serve as input into a trend-based analysis (ICES 2 over 3 rule).

For the stock in Icelandic and Greenlandic waters (aru.27.5a14), a category 1 Gadget-based assessmentmethod was presented and approved by reviewers.

For the stock mainly in Faroese waters (aru.27.5b6a), a category 1 SAM-based assessment methodwas presented and approved by reviewers.

For the stock in Norwegian and northern European waters (aru.27.123a4), a category 3 assessmentmethod using SPiCT was examined. The data were found still to be too limited to recommenda SPiCT assessment to provide reference points in advice for the stock at this point. However,the output from SPiCT as an input to the 2 / 3 rule was considered as a basis for advice,along with LBI analysis for fishing pressure, and approved by reviewers.