Book excerpt: Discards – the part of the catch that is not retained on board, which may include target species or any other (commercial and non-commercial) species that are returned at sea dead or alive – usually result in a reduction of harvesting opportunities and may have negative consequences on the stocks, ecosystems and the marine environment. In the Mediterranean and the Black Sea, studies on discards only cover a small portion of the total fishing activities and discard rates are often poorly estimated or totally unknown. Information is lacking for many types of fishing gear, countries and GFCM subregions, and most available studies only cover relatively short periods and small areas. Discards therefore represent a major source of uncertainty about the actual fishing mortality rates of stocks. These knowledge gaps highlight the need to expand discard monitoring programmes and standardize practices, so to assess discards appropriately and address their important impacts. This publication and the methodology discussed herein aim to provide a framework for the development and implementation of an efficient, standardized data collection and monitoring system for discards through on-board observations, questionnaires at landing sites and self-sampling activities. It ensures minimum common standards for the collection of discards data and allows for repeatability and comparisons among fisheries across the region, thus offering a harmonized basis of knowledge, information and evidence for decision-making.