Book excerpt: This publication, developed by the Food and Agriculture Organization of the United Nations (FAO), with the active support of the World Customs Organization (WCO), builds on the Harmonized System: Nomenclature 2022 edition. It presents all possible classifications for fisheries and aquaculture products by species, with a full description of each HS code, to facilitate its use within the fisheries sector, including aquaculture. This publication does not modify the structure of the HS or modify species grouping, as it is an auxiliary tool to facilitate classification and enhance understanding of the HS system from the angle of fisheries and aquaculture products. This publication is divided into three sections: (1) the first section presents all species which are directly referenced in the HS, with commodity codes for all possible classifications of their products and treatments; (2) the second section lists all HS codes for fisheries and aquaculture products with an exhaustive and comprehensive description of each code; and (3) the third section is a new section of the HS Handbook, where photos of the most commercially important species are shown. Each image contains relevant information and singularities of each species – scientific name, FAO names, main characteristics, and distribution.