This European Standard specifies a standardised method for sampling fish in lakes, using benthic multi-mesh gillnets. The method provides a whole-lake estimate for species occurrence, quantitative relative fish abundance and biomass expressed as Catch Per Unit Effort (CPUE), and size structure of fish assemblages in temperate lakes. It also provides estimates, which are comparable over time within a lake and between lakes. This European Standard specifies routines for sampling, data handling and reporting, and provides information on applications and further treatment of data. This standard is one of several European Standards developed for evaluation of species composition, abundance and age structure of fish in rivers, lakes and transitional waters. Other standards describe "Sampling of fish with electricity" (EN 14011), "Guidance on the scope and selection of fish sampling methods" (EN 14962) and "Guidance on the estimation of fish abundance with mobile hydroacoustic methods" (EN 15910). In most countries the use of the method specified in this European Standard requires permits from landowners and national or regional authorities. In many countries permits are also required from authorities for animal rights and animal welfare demands. Both fish diseases and diseases specific for other organisms, such as freshwater crayfish, may be spread by placing equipment contaminated with pathogens or parasites in the lake. The user of this method should check which national legislation is applicable. The preparatory work for the standard has been carried out by Working Group "Biological Methods" (WG 2) of CEN/TC 230, led by BSI (secretariat: United Kingdom). Subcommittee NA 119-01-03-05 UA "Biologische Verfahren" ("Biological methods") of NA 119-01-03 AA "Wasseruntersuchung" ("Water analysis") at DIN Standards Committee Water Practice (NAW) collaborated for Germany its preparation.