For many years there have been concerns that some forms of fisheries subsidies may complicate sustainable fisheries resources management by promoting overcapacity and overfishing. This OECD paper assesses support to the fisheries sector and proposes classifying these according to their degree of impact. It also provides a review of the past literature on the nature and effects of support to the fisheries sector, including a preliminary analysis to identify the factors that determine how support can affect overcapacity and overfishing, including illegal fishing, along with their likely benefits. The report is based on the latest OECD inventory of support policies in 31 participating countries, which represent 35 percent of global fisheries landings by volume. The report is available to download on the OECD website.