臺灣博碩士論文加值系統

　　攔砂壩為台灣河川上游重要的治山防洪設施，目前其數是大約有3000座左右，規模大小不一然而有關攔砂壩對河川生態影響之報告卻相當少。台中縣的鳥石坑溪為大安溪的一重要支流，流長約12公里。民國76年至78年間林務局東勢林管處在鳥石坑溪共建有7座攔砂壩及附設9座魚道。本研究從民國84年7月至86年5月止，在1號、2號、3號及7號攔砂壩上下方水域共設8個採樣站。調查蒐集各攔砂壩上下方水域的環境因子，包括河寬、水深、流速、流量、底質石。及水溫、水中溶氧含量、導電度、總固體溶解量、pH值。魚種組成、族群結構及豐度分布的差異，以究明攔砂壩對河川生態的影響，並評估其魚道功用，同時也用標籤標識放流的方法在其中3號壩的魚道試驗以驗證魚道功能。
　　對鳥石坑溪的洄游魚類而言7.5公尺到13公尺高的攔砂壩，無疑地構成障礙。攔砂壩除了限制魚類的洄游外，同時也改變了原來河道的物理環境及水質，自然就影響了河川的生態及魚類生活。由於攔砂壩上方很快就會填滿砂石，河床坡度減緩，流水面加寬，水深變淺，流速變慢，加速了水中溶氧量及水溫的變動，這種物理環境及水質的變動在乾季特別地明顯。除外攔砂壩的下方河床受水流掏挖，兩岸侵蝕嚴重，水濁度及總固體溶解量增加，這種現象以雨季較為明顯。
　　鳥石坑溪共紀錄8魚種，其中以台灣鏟頷魚(Varicorhinus barbatulus)最優勢，整年繁殖，成魚有季節性的洄游現象，在雨季的末期大約10月成魚上溯，而在雨季初期3月左右往下遷移；由攔砂壩上下方水域分布之台灣鏟頷魚月別及採樣站間體長頻度分布的資料，及標識放流的結果證明台灣鏟頷魚確實可以經由現有之水池式魚道上溯洄游至攔砂壩上方水域。平鰭鰍科的台灣間爬岩鰍(Hemimyzon formosanum)，頭、胸及腹部合成一扁平的吸盤，使其可以抵抗水中急流，與台灣鏟頷魚幾乎同時上溯，以其特殊的型態不需要經由魚道，亦可攀爬攔砂壩上溯至壩上方的水域。其他6魚種包括褐吻□虎(Rhinogobius brunneus)、短吻□虎(Rhinogobius rubromaculatus)、台灣馬口魚(Candidia barbata)、台灣石□（Acrossocheilus paradoxus）、粗首□（Zacco pachycephalus）及脂鮠(Leiocassis adiposalis)皆為原生種，偶而出現在鳥石坑溪，雖然在1號攔砂壩上游亦有紀錄，但其數量紕台灣鏟頷魚及台灣間爬岩鰍少。
　　雖然資料顯示一些魚種可經由魚道或攔砂壩上溯至魚道上方水域，但是魚種數有向上游減少的現象，同時在攔砂壩上方水域部份魚種體形大於下方體形（如臺灣鏟頷魚及台灣間爬岩鰍），此外台灣鏟頷魚在乾季攔砂壩間有較高的死亡率等現象，這些說明了攔砂壩對河川生態，無論是物理環境、水質或是魚類生活確實有負面的影響。
　　為了減輕攔砂壩對河川生態的影響，本研究建議為維護現有魚道，維持正常功能、以簡易式魚道替代、拆除現有攔砂壩及魚道及以連續性矮壩替代現有的高壩等4個方案並加以討論。綜合生態及工程的需求，其中以連續性矮壩替代高壩，雖然減少了攔砂量，但既可解決現有魚道功能不彰及減低壩高阻礙外，亦可增加控制水流（連續消能）的能力，減輕對壩下侵蝕掏挖的能量。

　　Wushykeng Creek is a 12-kilometer long mountain stream, a tributary to the Daan River, situated in the Taichung county in the central portion of Taiwan. In 1987-1989 the Taiwan Forestry Bureau constructed seven check-dams (sabo-dams) for the stream bed stabi ization, with nine fishways. From July 1995 to May 1997, the stream survey was conducted at eight stations to collect data on physical environment (stream flow, stream width, water depth, water velocity, bottom substrate, and shore line conditions), water quality (water temperature, dissolved oxygen content, pH, and conductivity and total dissolved solids) and fishes (species composition, and population structure and abundance) to assess the impacts of the check dams on stream ecosystem, and to evaluate the effectiveness of the fishways for fish passage. For the latter fish were also tagged and released immediately downstream from one of the fishways to assist the evalu tion.
　　The check dams had the heights of 7.5m to 13m, and undoubtedly became barricades for the upstream migration of fishes in the wushykeng Creek. In addition to their blocking fish migration, the check dams altered stream physicale nvironments and water quality, adversely affecting the stream ecosystem and fish life. In the immediately upstream areas of the dams, rocks and gravel were piled up, that rifted up the surface flowing stream, decreased its slope, water depth, water flow velocity, dissolved oxygen contents, and fluctuated its water temperature. The alternations of stream physical environments and water quality were particularly obvious in the dry season. In the downstream area, the water poured down the dams, deelpy excavated the downstream bed, and increased the shore erosion, water turbidity and dissolved solid contents. These downs tream alternations of the environment were most serious in Wusheykeng creek, of them Varicorhinus barbatulus (Family Cyprinidae) was most dominant. It was a resident species, spawning apparently throughout the year in the creek, but the mature fish showed seasonal migration: upstream migration at the end of the summer raining season (around October) and downstream migration at the beginning of the raining season (around March). Based on the monthly and longitudinal variations in the length frequency distribution of fish collected above and below the dams and on the results of the tagging experiment, there were strong evidences that V. barbatulus was able to pass the check dam(s) by utilizing the existing fishways (pool type) for its upstream migration.
　　Hemimyzon formosanum (Family Homaloperidae) apparently spawned outside the Wushykeng Creek, but some of the fish migrated to the creek at the end of the raining season for feeding during the dry season. Its body is equipped with an specific adherent apparatus formed by the ventral portion of body and laterally expanded pectoral and pelvic fins. This apparatus enables this species to attach itself on rocks in the rapid flowing creek. There were some evidences in this study that large fish (>5 cm) of this species may be able to climb directly over the check dams in its upstream migration.
　　The other six species included Rhinogobius bruneus, Rhinogobius rubromaculatus (Family Gobidae), Candidia barbata, Acrossocheilus parodoxus, Zacco pachycephalus (Family Cyprinidae), Leiobargus adiposaris (Family Bagridae). Of these species, R. bruneus like V. barbatulus was a resident species, occurring in the entire creek. The other species occurred in the downstream and were considered as occasional visitors for the Wushykeng Creek. Some fish of these species were also found in the Wushykeng Creek. Some fish of these species were also found in the upstream from the first check dam, indicating that these fish may also pass the fishway for the upstream migration, but lesser than those of V. barbatulus and H. formosanum.
　　Although there were evidences of successful passage of fishes through fishways mentioned above, the number of species and the abundance of fish in the creek showed decreases from downstream to upstream. Also, there was high mortality of fish in the section The results of this study suggested that the check dams in the ishykeng Creek adversely affected the physical environments, iter quality and fish life. In order to mitigate the adverse ffects, the following four approaches may be considered:
　　1.Repair existing fishways and develop a management program to maintain their proper function.
　　2.Replace existing fishways with portable fishways.
　　3.Remove existing check dams and fishways.
　　4.Replace each of the existing check dams and fishways with a series of low check dams, that are also functioned as a fishway.
　　For a long-term and cost-effective consideration, the fourth mitigation approach is recommended