台灣東部秀姑巒溪大和沼蝦（Macrobrachium japonicum）幼體全日上溯特性初探

Aspects of all-day upstream migration of juvenile Macrobrachium japonicum in the Hsiukuluan River, eastern Taiwan

台灣大部分淡水沼蝦為兩側洄游之生活史，其幼苗需在河口或沿岸地區經一段時間的變態成長剛著底具爬行能力時，再上溯回河川繼續成長。大和沼蝦（Macrobrachium japonicum, de Haan, 1849）為兩側洄游型之物種，在台灣為廣分布物種，數量豐富，迄今尚無有關上溯洄游之研究發表。本研究初步於2005年6月14日至15日在秀姑巒溪，利用改良式的採樣設備，採集大和沼蝦幼體，探討其全日之上溯特性。結果顯示大和沼蝦全日主要有2個上溯時段，最高峰時段為下半夜至清晨（03:40-07:40），其次為午後近黃昏至初夜（15:40-19:40），除19:40-23:40外，餘時段皆有零星上溯個體。本研究的採樣設施共採集大和沼蝦（M. japonicum）、熱帶沼蝦（M. placidulum）、寬掌沼蝦（M. lepidactyloides）及闊指沼蝦（M. latidactylus）等4種沼蝦，幼體占比約94%，十分適合上溯試驗之採樣工具。本研究將有助於未來持續進行長期各種沼蝦之上溯研究，尤其台灣大部分的沼蝦物種尚待釐清的洄游特性。

Most Macrobrachium spp. are amphidromous in Taiwan. After larval development, the newly-metamorphosed individual must find a river mouth and migrate back up to the adult habitat. The Macrobrachium japonicum de Haan, 1849 is a widely distributional, amphidromous, and abundant specie in Taiwan. This study clarifies the upstream migration patterns of M. japonicum using a modified fish-trap for sampling juvenile in the Hsiukuluan River of eastern Taiwan from 14 June to 15 June 2005. The interval of collecting time were divided into six periods in a day—A:15:40-19:40, B:19:40-23:40, C:23:40-03:40, D:03:40-07:40, E:07:40-11:40, and F:11:40-15:40. There are two distinct upstream migratory periods. The highest peak is near dawn from 03:40 to 07:40 and the second peak is near dusk from 15:40 to 19:40. The 94% of total collected individuals were juvenile, so the modified fishway trap is suitable equipment for conducting experiments on upstream migration of freshwater prawns. The results of this study will be helpful for understanding the upstream migration of Macrobrachium spp. in Taiwan.