台灣細鳊Rasborinus formosae（Oshima, 1920）之人工繁殖及幼苗發育研究

Artificial Breeding and Larval Development of the Taiwan Lesser-Bream Rasborinus formosae (Oshima, 1920)

台灣細蛇Rasborinus formosae（Oshima, 1920）為原來普遍分布於淡水河水系緩流區及湖泊的小型魚類，由於棲地破壞、污染與外來種干擾等因素，使其族群面臨嚴重威脅，並有滅絕危機。本研究藉由人工催熟與自然產卵的方式進行台灣細蛇的繁殖試驗，並進行育苗觀察與記錄，以瞭解台灣細蛇之繁殖過程、生殖習性與魚苗成長過程，期望逐步建立台灣細蛇之基礎生物學資料，並應用於自然環境中之復育或人工繁養殖。由實驗得知，台灣細蛇的魚卵卵徑約1.1 mm，為沈性帶黏性卵，在水溫24-28℃的環境中約23-25 hr孵化，初孵化的魚苗體長約為3.8 mm，魚苗在孵出第4天開始攝食餌料。尾鰭於第6天開始發育，背鰭於第10天開始發育，腹鰭第19天發育，第28天可清楚觀察到鱗片長出。 Taiwan lesser-bream Rasborinus formosae (Oshima, 1920) is an endemic freshwater fish, occurringin a few mountain ponds and brooks along tributaries of the upper Tanshui River in the northern Taiwan.It has been very rare in Taiwan, owing to its habitat destruction, water pollution, and irruption of exoticfishes. This study was the first step for the conservation of R. formosae. We conducted artificial breedingof the fish and observed its embryonic and larval development. Egg diameters were about 1.1 mm. Larvalhatched at 23-25 hours after fertilization at water temperature of 24-28℃. Total length of newly hatchedlarvae was about 3.8 mm. The larvae began feeding on 4 dah (days after hatching). Caudal fin developedon 6 dah, dorsal fin on 10 dah, pelvic fins on 19 dah, and scales clearly observable on 28 dah.