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The ICES survey protocol for offshore beam trawl surveys describes the current methodologies, stratification and sample processing used in the offshore beam trawl surveys that provide fisheries-independent information to the fish stock assessments for a variety of flatfish species. The surveys are conducted by Belgium, France, Germany, Iceland, Italy, Slovenia, Croatia, the Netherlands, and UK (Cefas). The manual also contains (i) an overview of the major historical changes in survey methodology and/or data collection, and (ii) an overview of the main attention points for data-users, e.g. when combining the data of the respective beam trawl surveys, and recommended data processing. The impetus for all the beam trawl surveys in this manual is the need for fisheries-independent information on commercial flatfish species. The prime target species and type of beam trawl are set depending on the survey area and/or the relevance of the species for the national or EU fisheries. Over time, data collection within the surveys has expanded due both to a shift towards a more ecosystem-related general focus and to new data requests by end-users. As a consequence, the collection of epibenthos data has become more detailed over time and age data are collected for more species than at the time the surveys were developed. The current survey objectives are similar for all areas: • Data collection to create fisheries-independent abundance indices by age group (1‑year olds and older) for a number of fish species [e.g. plaice (Pleuronectes platessa), sole (Solea solea), dab (Limanda limanda), lemon sole (Microstomus kitt), flounder (Platichthys flesus), turbot (Scopththalmus maximus), brill (Scophthalmus rhombus), and monk fish (Lophius spp.)] for the sampled area. • Data collection to create fisheries-independent abundance indices for mantis shrimp (Squilla mantis), caramote prawn (Mazzancolla sp.), and common cuttlefish (Sepia officinalis) in the Mediterranean Sea. • Collection of biological data, including length measurements, on all fish species, including elasmobranch species, for ecosystem analysis purposes. • Collection of data on at least a selection of epibenthos species for ecosystem analysis purposes. • Collection of environmental data (at least temperature and salinity). • Collection of marine litter data. The present document is the 4th edition of the survey protocol. The manual has its origin in national manuals for offshore beam trawl surveys, and can be considered the public version of the national manuals.