The slender tuna, Allothunnus fallai, is a species of tuna, the only species in the genus Allothunnus, found around the world in the southern oceans between latitudes 20° and 50° South, although there are two records of probable vagrants, one in Los Angeles Harbour and the other from the North Pacific subarctic gyre. It has a more elongated body than other species of tuna with which it is symaptric such as the albacore The colour is blue-black on the back with silvery greyish-white sides, however some individuals have a coppery sheen soon after capture. It has a small second dorsal and anal fins resembling a small albacore, but the slender tuna lacks the long sweeping pectoral fins characteristic of albacores.
Allothunnus fallai is a slender species of tuna belonging to the genus Allothunnus, found in the southern oceans between 20° and 50° South latitude. There are two records of probable vagrants: one in Los Angeles Harbour and another from the North Pacific subarctic gyre. This fish has an elongated body compared to other sympatric tuna species like albacore, with dark blue coloring on top and silvery greyish-white sides. Some individuals display a coppery sheen immediately after capture. It features small second dorsal and anal fins that resemble those of an albacore but lacks the long sweeping pectoral fins characteristic of albacores.