北九州におけるアブラハヤの生活史(I) Studies on the life history of the Aburahaya, Moroco steindachneri steindachneri (Sauvage), in northern Kyushu (I)
The Aburahaya, Moroco steindachneri steindachneri (Sauvage), is a cyprinid fish, distributed widely in Japan except in Hokkaido. This fish prefers to rather lower water temperature and is found in the upper and middle course of the rivers. In the present paper the authors reported mainly external features, food and early life history of this fish in northern Kyushu, especially in Haccho River, a tributary of Muromi River, near Fukuoka City, through 1958 to 1959 (Fig. 4). Although some local forms of the Aburahaya have been reported, the characteristics of the fish in this district coincide approximately with Moroco steindachneri steindachneri which is adopted by Matsubara (1955) (Tab. 2). The adults are found usually in the pools and the stagnant waters in the river and are very active in summer. They have a tendency to become quiescent in winter and are hiding among the aquatic plants and under the stones on the shore. The intestinal contents of this fish were examined in May (Tab. 4). This fish is omnivorous and the most important food is aquatic insect. The spawning occurred from April to August in this district at 12-20℃ (Fig. 3). The authors observed the nuptial coloration in male; a grey or black band arising on the snout and terminating at the base of the caudal fin (Fig. 5). The courtship was observed in the aquarium and the eggs were spawned in the sandy bed. The egg is spherical in shape, 2.1-2.3 mm in diameter with yellow yolk and slightly adhesive. The egg membrane is transparent, but becomes opaque in the course of the development. The incubation period continued for 3 days at the water temperature about 20℃. Newly hatched larvae are about 5.1 mm in total length (Fig. 6, C), and in 10 days after hatching the larvae almost consumed the yolk (Fig. 6, D) and in this stage they seem to swim out from the spawning bed in natural condition. The larvae hatching in May attained about 60 mm in total length in December. Field observations on larva, juvenile and young fish during summer season reveal that they are tend to change their habitats from the shallows to the deeps as their growth (Fig. 7).筆者らは北九州産アブラハヤの生活史のうち成魚の形態と生態,初期生活史を報告した.その結果は次のようにまとめることができる. 1 北九州産アブラハヤの形態は松原(1955)のMoroco steindachneri steindachneri (Sauvage)にほぼ一致する. 2 室見川水系の八丁川においては成魚は瀬には少なく,淵頭や堰の上のゆるやかな流れのところ,淀み,淵に多く生息し,夏李には活発であるが冬季は不活発でものかげにかくれている.生息適水温は10℃～20℃である. 3 アブラハヤの食物は主として昆虫であるが植物もふくみ,きわめて貪食である. 4 産卵期には雄の体側に側線に沿うた暗色縦帯が現われる. 5 八丁川におけるアブラハヤの産卵期は4～8月で,その期間の水温は12～20℃ である. 6 卵は2.1～2.3mmの弱粘着性球形卵で,発生の途中で卵膜は不透明になる.水温約20℃では3日で孵化し,孵化仔魚は全長約5.1mm, 孵化後10日で卵黄を吸収する.5月に孵化したものは同年12月には全長約60mmに達した. 7 アブラハヤは発育とともに生息場をかえ,仔稚魚期には岸近くの浅くて流れのゆるやかなところ,淀み,淵などに多く生息するが,発育が進むにつれて流れのあるところへ出て生息するようになる.
九州大學農學部學藝雜誌 21(1), 123-130, 1964-02