ABSTRACT
Considering the present status of the composition of this suborder, the authors examine three families under it: Scombridae, Istiophoridae, and Xiphiidae. Members of genera of these families are either pelagic and mainly predators, living mostly in open parts of the ocean, or neritic and found above the slope of large depths. The biology of members of the suborder Scombroidei has been studied by Rass, Osipov, and Gorbunova. Japanese ichth jologists, noting that the external characters of tunas vary with age, have developed three keys of species of this genus; one is based on external characters and the other two on anatomical features. Teeth better developed and more numerous than in the genus Katsuwonus; present not only on jaws but also on palatines and sometimes on vomer; teeth on palatines arranged in single row. Studies on the blood composition of Atlantic and Pacific skipjack tunas deserve attention, as they establish interpopulation differences within the species.
