清水溪台灣特有種明潭吻鰕虎（Rhinogobius candidianus）攝食生態

Feeding Ecology of the Endemic Goby (Rhinogobius candidianus) in Chinshui Creek, Taiwan

本研究爲了解台灣特有種明潭吻鰕虎攝食習性，自2008年11月至2009年10月間，每月於濁水溪支流的清水溪流域以12伏特電魚器進行樣本採集，並檢測其胃內容物組成。期間共捕獲明潭吻鰕虎1,103尾，最小與最大個體體長分別爲1.70 cm及7.73 cm。結果顯示，該流域於乾季水流量低且穩定，故食物種類豐富，致使乾季空胃率（3.83%）低於雨季的空胃率（16.24%）。明潭吻鰕虎屬於雜食性魚類，各月份間胃內容物種類相對重要指數（RI）之群聚分析結果顯示，主要以水生昆蟲、有機碎屑與絲藻片段爲主，各季節攝食食物種類相似度達40%以上。該魚攝食習性會隨著不同成長階段而改變，其主要攝食種類由水生昆蟲轉變爲絲藻片段，且攝食種類會因乾季、雨季和颱風的影響而有明顯的差異，提供明潭吻鰕虎攝食生態，做爲保育溪流生態之參考。

In order to examine the feeding ecology of the endemic goby Rhinogobius candidianus in Chinshui Creek, a tributary to Choushui River in Taiwan, the fish was sampled monthly with a 12-volt electric fishing gear from November 2008 to October 2009. A total of 1,103 individuals of the fish with the body sizes ranging between 1.70 cm and 7.73 cm were collected, and their stomach contents were examined. Number of fish with empty stomach was 3.83% in the winter dry season while 16.24% in the summer monsoon season. Apparently, the winter dry season of low stream flow provided a stable stream environment with abundance of food for the fish. R. candidianus is omnivorous fish consuming primarily filamentous algae, insects, and detritus. Relative frequency occurrence and abundance of these three food items varied with time, and composed more than 40% of the similarity relative indices. The diet composition varied significantly with fish sizes, showing a shift of diet from aquatic insects to filamentous algae with the growth. The composition also varied significantly between the summer monsoon season and winter dry season, and strongly affected by typhoon events.