Northwest European Shelf Cod Stocks; North Sea, West of Scotland, Irish Sea and Celtic Sea

This chapter describes the cod stocks on the northwest European shelf. Cod in this region have the highest growth rates of any stock, linked to high temperatures and prey availability. Due to their relatively high juvenile mortality and fast growth rate most of these cod mature early. Historically, fishing mortality was the main driver of changes in the stocks. However, warming, particularly in the south has had an adverse effect on recruitment due to effects on growth and expanding predator range. Contrary to past distributional evidence, electronic tagging demonstrates that adult cod are not moving away from warming waters. While the main approach to fisheries management is focussed on catch quotas, with annual advice from ICES, a range of measures of restricting access to high cod densities using short, seasonal and long-term closed areas have been tried, with varying success. Based on recent evidence on genetic structuring and movements, ICES merged the West of Scotland and North Sea stocks into a northern shelf stock with three sub-stocks in 2023. The northwestern sub-stock, which straddles the former West of Scotland and northern North Sea has been the most stable while the southern sub-stock has sharply declined since 2016.