口永良部島におけるトラギス科・エソ科魚類の食性

南西諸島口永良部島の磯水域においてトラギス科2種、オグロトラギス Parapercis polyophtalma、ワヌケトラギス Parapercis cephalopunctata、エソ科魚類4種、オキエソ Trachinocephalus myops ミナミアカエソ Synodus variegatus、マダラエソ Saurida gracilis、マエソ Saurida sp. の胃内容物を調査した。トラギス科・エソ科とも岩・死サンゴ岩盤上、転石、小石場、砂地に生息しており、海底に静止し近づいてきた餌に飛びついて捕らえる待ち伏せ型の摂餌方法をとる。双方の魚類とも主な餌生物は底生性の甲殻類、魚類であるが、ワヌケトラギスでは小型個体は底生性魚類も摂餌するが、成長に伴い甲殻類中心へと食性が変化するのに対し、オキエソでは成長に伴い甲殻類から表層性魚類ヘ、ミナミアカエソでは成長に伴い底生性魚類から表層性魚類へと食性が変化した。

The guts contents of two species of penguipendid fishes, Parapercis polyophtalma and Parapercis cephalopunctata, and four species of synodontid fishes, Trachinocephalus myops, Synodus variegatus, Saurida gracilis and Saurida sp. in shallow reef water around Kuchierabu-jima Island, southern Japan, were analyzed. Both penguipendid and synodontid fishes commonly inhabit on rocks, dead coral, boulders, gravel, and sand paches in the reef. They are typical ambushers which rest immobile on the sea floor and suddenly attack prey which come within striking distance. They preyed mainly on demersal small crustaceans and small fishes. In penguipendid fish, although smaller fish of P. cephalopunctata preyed on fish and small crustaceans, larger ones preyed mainly on small crustaceans. In synodontid fish, feeding habits of T. myops changed with fish growth, from small crustaceans to pelagic fish, and that of S. variegatus changed with fish growth, from demersal fish to pelagic fish.