南緯40° 付近で獲られる二種のマグロ類似の魚類について
1966 年 14 巻 1-3 号 p. 41-48
詳細
1966 年 14 巻 1-3 号 p. 41-48
Specimens of Gasterochisma melampus RICHARDSON and Allothunnus fallai SERVENTY were obtained by the Japanese long-line method from off Tasmania (45° 30'S, 140°E) in 1963 and from off Uruguay (40°S, 40-50°W) in July, 1965, and brought to the Misaki Fish Market, Japan. Noteworthy additions to the knowledge of these two little-known fishes are:
Gasterochisma melampus. More than 60 individuals weighing about 4 tons in all were captured by long-lines (bait: Cololabis saira) during less than two weeks at approximately the same fishing ground off Uruguay.
Gill rakers on the outer row of the first gill arch are granular and equipped with sharp spines. The numbers of the principal rakers are 17 on the lower limb, 1 at the angle, and 8 on the upper limb. Smaller auxiliary rakers are distributed irreg ularly between the principal rakers. There are scales buried in the skin on the occiput. These may have been overlooked by WAITE (1913), who reported that the scales on the occiput disappear in the adult.
In the stomach of an Uruguayan specimen (ZIUT 52, 313), numerous pelagic amphipods of 15-20mm, and half-digested skeletons of Alepisaurus were observed.
Allothunnus fanai.The report of the Uruguayan specimens given here re presents the first record of this fish from Atlantic side of South America.
Anterior nostril is very small and barely visible to the naked eye: posterior nostril is slit-like. In a Tasmanian specimen, 87cm in fork length, the areas under the lateral line are scaled partly or entirely. The base of the caudal fin is also scaled.
