The swimbladders of about 300 species of percoid and other teleostean fishes were examined with special reference to the presence or absence of a posterior extension beyond the postcoelomic wall of the body cavity. In addition, a comprehensive survey of literature dealing with swirobladder structure was made for comparative purposes.

Swimbladder morphology varied between families, with differences in the vertical position, shape of the posterior end, median septum, membrane strength and shape of the transverse section. In many percoid fishes, as in many other teleostean species, the swimbladder is contained completely within the body cavity. It extends into the myotomes of the caudal region in the Callanthiidae, Kuhliidae, Malacanthidae, Lactariidae, Menidae, Monodactylidae, Coracinidae, Kyphosidae, Girellidae, Scorpididae, Microcanthidae, Pomacanthidae, Oplegnathidae and Embiotocidae. A posterior extension of the swimbladder occurs in some members of the Centropomidae, Centrarchidae, Priacanthidae, Leiognathidae, Lutjanidae, Haemulidae, Lethrinidae, Sparidae, Centracanthidae, Ephippidae, Chaetodontidae, Nandidae, Cichlidae, Pomacentridae, Owstoniidae and Cepolidae. In the Sillaginidae and Carangidae, in those species possessing a swimbladder, a posterior extension may or may not be present, whereas all members of the Serranidae, Percidae, Mullidae and Pempherididae which possess a swimbladder, lack a posterior extension. No swimbladder was found in the Plesiopidae, Acanthoclinidae, Rachycentridae, Echeneididae, Coryphaenidae, Bramidae, Caristiidae, Leptobramidae, Parascorpididae, Rhinoprenidae, Cirrhitidae, Chironemidae and Aplodactylidae. Considered overall, it appears likely that the posterior extension of the swimbladder is a useful character for phylogenetic studies of percoids.