Fusiliers (Caesionidae) are a family of the order of Perciformes that owe their name to the Latin word caesius, whose meaning is grey-blue, in allusion to the coloration of their body. They are exclusively marine fishes, whose distribution includes the eastern Indo-Pacific. They are species of diurnal habits and are closely related to the family of Snappers.
The body of Fusiliers is somewhat oval and very streamlined. Moderately compressed in the lateral plane and with a size that we could classify as between medium and small. The maximum length of Fusiliers is 60 cm, although the vast majority of species do not exceed 30 cm in length. The eye, moderately large (its diameter is longer than the length of the snout) is located exactly on the longitudinal axis that goes from the tip of the snout to the middle of the tail fin. The mouth is small, highly extendible and slightly upwardly oriented. In relation to the colouring of Fusiliers, their flanks may or may not have longitudinal stripes. They have mostly a blackish spot on the tips of the tail fin lobes, or a longitudinal stripe also blackish in the center of each of the tail fin lobes. The pectoral fin armpit, i.e. the region where the pectoral fins join the body of the individual, is usually blackish in color.
The dorsal fin of Fusiliers is unique and continuous. It is formed by 10-15 thin spines, followed by 8-22 soft spokes. The third and fourth spines are the longest, and from these both the spines and the rear spokes gradually decrease in height. The anal fin is formed by 3 spines and 9-13 spokes, being the third spine the highest one, and from it the following spokes are reducing gradually their height. The pelvic fins have 1 spine and 5 spokes. The pectoral fins have between 16 and 24 spokes. The caudal fin is very bifurcated and its lobes are pointed.
Fusiliers are planktivore fishes that filter the water through their specially modified jaws to capture plankton. There are currently 23 species within Fusiliers family, which are organized into 4 genera.