Geographic Variation in the Central Pacific Halfbeak, Hyporhamphus acutus (Gunther)

Abstract

Hyporhamphus acutus (Gunther) is distinguished from other Central Pacific species of Hyporhamphus by its long upper jaw, long anal fin base (longer than dorsal base), and shape of its preorbital lateral line canal. Two subspecies are recognized: Hyporhamphus acutus acutus (Gunther) with fewer vertebrae and fin rays inhabits the chain of islands from Wake Island and the Marshall Islands in the northwest to the Tuamotu Archipelago and Easter Island in the southeast; Hyporhamphus acutus paciftcus (Steindachner) with more vertebrae and fin rays is found in the Hawaiian Islands and at Johnston Island. Hemiramphus furcatus Philippi from Easter Island and Odontorhamphus chancellori Weed from the Cook Islands are placed in the synonymy of Hyporhamphus acutus acutus.