Book excerpt: This identification guide includes 552 species of mesopelagic fishes (i.e. those fishes residing primarily between 200-1000 m depth during daytime) that are known to occur in the central and south east Atlantic Ocean. Fully illustrated dichotomous keys to all taxa are provided. Species are treated in detail, with accounts including the scientific name, FAO common name in English (where available), other useful characters, size, a distribution map, and one or more illustrations. To facilitate even further the identification of the taxa, captions and arrows are added to help users quickly locate their key morphological features. The guide is intended for both specialists, and nonspecialists who have a working knowledge of ichthyology.