Egg production methods applied to Eastern Baltic cod provide indices of spawning stock dynamics

•Egg production methods have been used for assessing the Eastern Baltic cod stock.•The analysis contributed to the re-establishment of an analytical assessment for the stock.•Annual and daily egg production methods gave similar results.•Results confirmed trends from trawl surveys, questioned earlier because of potential change in catchability.•Several biological processes impact on absolute spawning stock estimates and research needs are identified to improve these.