探討多因子影響台灣石鮒棲地以改善灌溉渠道生態設計

Abstract

台灣石鮒為台灣原生種，在水質乾淨的圳路裡常常可以看見台灣石鮒的蹤跡，其對於水質環境變異相當敏感。此外，台灣石鮒喜愛於水庫、埤塘與圳路之間洄游，因此我們可以將台灣石鮒作為探討圳路是否能做為水源地及下游溪流之生態廊道的指標。 因子分析結果顯示，台灣石鮒選擇寡養水源、少無機鹽且具一定流速溶氧的水域環境。依據forage ratio選擇性比例研究可知梯形斷面為台灣石鮒偏愛的渠道類型。由於梯形斷面較能維持一定水流深度，且相對於U型渠道可產生流速的多樣性，也連帶的稀釋污染因子及增加溶氧，使得台灣石鮒偏愛。台灣石鮒出現頻率最高的平均流速為0.35m/s左右，而流速全距及流速多樣性則隨著數值的增加而增加。 室內實驗研究結果顯示：台灣石鮒的臨界游速介於0.18至0.42(m/s)之間，若將臨界流速以單位時間內體長來計算，台灣石鮒平均值為5.59 1.20。台灣石鮒尾鰭擺動頻率也會隨流速增加而增加。

Tanakia himantegus is one of native species in Taiwan. It can be found in irrigation channels where water quality is good and it is sensitive to aquatic environment. Furthermore, Tanakia himantegus prefers to migrate between reservoirs, ponds and irrigation channels. Consequently, Tanakia himantegus is a good indicator species of ecological corridors. According to the factor analysis, Tanakia himantegus prefers to live in irrigation channels with oligotrophy, low inorganic salt and high speed aquatic environment. Forage ratio shows that Tanakia himantegus prefers to live in trapezoid irrigation channels. Because of speed diversity, trapezoid channels have a higher dissolved oxygen and dilution efficiency of pollutants compared to U-shaped channels. It is also much easier to maintain the water depth in dry season. Tanakia himantegus is predominant in a flowing environment where average flow speed is 0.35m/s, and the appearing probability increases when speed diversity increases. Results of our laboratory experiment show that the critical swimming speeds of Tanakia himantegus were between 0.18 and 0.42m/s. Through dividing the critical swimming speed by the length of fishes, we obtained the average moving number in an unit time, which is 5.59 1.20.The tail-beat frequency increases when velocity increases, until the critical swimming speed.