溪流狀況指數(ISC)應用於上游野溪適宜性之研究

Abstract

溪流生態棲地之評估方式繁多，隨著領域及地區之不同，往往會有不同的選擇，本研究以人為破壞相對較下游河溪少、生態復育潛力相對豐富之上游野溪作為研究對象，選擇工程人員較易使用、兼具物理性、化學性及生物量化指標—由澳洲維多利亞省所發展之溪流狀況指數(Index of Stream Condition, ISC)評估模式。其中，針對水生物次指數作修正，以魚類作為水域生態之指標生物。 多元迴歸之逐步迴歸分析得到上游野溪指標魚類生長之棲地環境關鍵因子為水深、面積、體積、底質歧異度、pH值、電導度、雨量及海拔高度，以及關鍵因子與指標魚類體長、密度之關係。統計分析結果顯示指標魚類之體長差異及密度與關鍵因子關係顯著，藉此修正水生物次指數之評分項目。 以本研究修正之方法針對10 處野溪進行評估，並與蔡(2006)之模式進行比較，發現本研究更能反映出真實溪流狀況，且能避免完全否決未發現魚類時野溪之生態條件。 而上游野溪之現地調查次數及時間，以每季調查一次，時間為3、6、9、12月最為適合。同時，得到ISC 總分31 分為判別上游野溪溪流生態之臨界值：分數低於31 分為較差之指標魚類棲息環境；高於31 分者為較佳之棲息環境。

There are many kinds of assessments on ecological habitat of stream due to the different regions and localities. This study targeted at torrents, which have less contamination and more ecological potential restoration comparing with downstream ones and chose Index of Stream Condition, developed by the State of Victoria in Austria, which is included in physical, chemical and botanical indexes and easier use for engineers, especially. In which, The Aquatic Life Sub-index is modified by this study and is represented by fish species. By Stepwise Regression Analysis in Multiple Regression Analysis, the prominent habitat factors could be depth, area, volume , substrate diversity, pH , electrical conductivity and elevation as well as the relationship between these factors and fish length and its density. The result of statistic analysis showed that the relation between these prominent factors and the variety of body length and density of endemic fish species are significant. According to this result, the assessment of Aquatic Life Sub-index was modified for torrents in Taiwan. Ten torrents in Taiwan were assessed by the modified method, and the results were compared with Tsai’s one (2006). The comparison showed that the modified method by this study reflect the better result than Tsai’s one. And, the modified method can avoid rejecting the ecological conditions of torrents totally as no finding endemic fish species. Moreover, the investigation time and its frequency could be setup in each season in March, June, September and December. Besides, the criteria of Index of Stream Condition on torrents in Taiwan could be 31. In which, the index below 31 represents the worse habitat for endemic fish species while above 31 represents a better condition.