This identification guide includes 552 species of mesopelagic fishes (i.e. fishes residing primarily between 200-1000 m depth during daytime) that are known to occur in the central and southeast 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 characteristics, size, a distribution map, and one or more illustrations.

To further facilitate 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.