Population analysis and early development of the rare cyprinid fish, Metzia formosae(Oshima,1920) in Taiwan

• Main Authors: Wu, Cheng-Han, 吳承翰
• Other Authors: 陳鴻鳴
• Format: Others
• Language: zh-TW
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/e6j58h

碩士 === 國立臺灣海洋大學 === 水產養殖學系 === 106 === Rising human impacts and over-exploitation of industrial development in Taiwan have been caused the great damage and water pollution of natural habtats. Previous exploration in Taiwan showed that the freshwater fish Metzia formosae (Oshima, 1920) were inhabit in slow-flowing stream and ponds and distributed in the Tanshuei River and Yilan river basins. However, through recent intensive survey showed only found in the upstream of Yilan river, indicating its natural population continues to deteriorate. A total 54 of them have been collected from Yilan. Another locality, Mong Lake, with totally fish population as estimated 11,535 individuals. Two distinct mitogenetic populations can be detected from New Taipei City and Yilan County. In the early development study, five pairs of mature fish were selected. In the evening, the carp pituitary slurry administered at concentration 0.01g/50µl and applied to 10 µl. The eggs were transparent, sticky, sinking and sized 1.22-3.24mm (N=4). Hatching start occurred after 20 hours fertilization and all hatched after 24 hours. Body length (BL) of newly hatched larvae was 3.30 mm, with large yolk sac (60-70% of total length). 12 hours after hatching, BL was 3.92 mm, body extended and yolk sac 60% left. The melanocyte began distributed on the eyes, on the top edge of head shaped slender or oval, and on the abdomen shaped thin and irregularly curve. 36 hours after hatching, BL was 4.41 mm, melanocytes completely distributed on the eyes and more increase distribute around eyes and shaped round, oval or irregular thin strips. Melanocytes on dorsal and abdomen increased and shaped slender. Pectoral fins developed and anal structure became observable. 2 days after hatching (DAH), BL was 4.44 mm, distribution of melanocytes on the body’s longitudinal band was increase, extending from the rear of pectoral fins to the tail, mouth opened, gill lid formed, and pectoral fins developed. 14 DAH, BL was 6.09, melanocytes on the upper edge of the head was finely distributed, shaped round and elliptical, black spot appeared in the longitudinal band of body extending forward from the caudal stalk, soft rays of pectoral fins developed, nostril differentiated into two holes, and gill lid developed, soft rays of caudal fin observable. 29 DAH, BL was 9.26mm, melanocytes more increase around the eyes, also distributed on the snout. Pectoral, dorsal, anal and caudal fins were completely developed. 50 DAH, BL was 14.55, there was a large distribution of melanocyte on the head. Melanocytes on the dorsal and anal showed discontinuous strips, all fins were completely developed and vertical scales were observed. 70 DAH, BL was 21.33 mm, lateral-line scales began to develop, extending from the tail shank to the head. 135 DAH, BL was 47.36 mm, and melanocytes on the head were widely distributed, fins completely developed, lateral-line scales were completely developed with some melanocyte distribution.