碩士 / 國立清華大學 / 生物資訊與結構生物研究所 / 103 / Formosan landlocked salmon (Oncorhynchus masou formosanus) is a valuable protected species, but its last habitat, Chichiawan Stream basin, was built up numerous sabo dams, which has impacted both environment and ecosystem. By using the population monitoring data in past 20 years, this study set up a population-estimating model, in order to compare the change of the population and environment before and after the destruction of the dam #2 in Chichiawan Stream. In addition, the model also provides an efficient way to simplify the investigating work in the future.
For the purpose of focusing on the single variable, dam, the data have to calibrate first, to eliminate the influence of other environmental impacts. However, there was less significant difference for the statistic results of the calibrated data. Since the sabo dams might amplify some negative impacts, such as high water temperature or typhoon, the calibration will reduce the significance of the results and the fitness of the models.
The results of statistic tests show that the population in the upstream increased significantly after the destruction of the dam #2, because the population in the downstream were tend to trace to the cooler upstream, and the sediments from the dam destruction will impact the physical habitats in the downstream persistently. For the comparison of three age-classes, the small fishes were increased significantly, which proved that dam #2 blocked the pathway for reproduction. In addition, the results of the population-estimating model about the dam also showed that the small fishes increased when the dam wasn’t existed. In contrast, the number of the other two age-classes decreased slightly due to the competition of the increasing small fishes. Nevertheless, the population structure became pyramid-shaped, which means that the undamming streams benefit the renewal of the population.
According to the reference, this study inferred that the destruction of the dam #2 might need more time to recover, because the recovery of ecosystem depends on stability and diversity of the habitats. Furthermore, the incessant typhoons and the easily collapse geology lead to the dramatic change of the habitats in Chichiawan Stream, so it’s difficult to find a significant difference from the statistic results, even though ten years has passed. In spite of the long recovery, we should remove the rest of the dams to return natural habitats to the salmons.
The population-estimating model can estimate the total population from the “model section”. For the single model section, dam #1 to dam #2, dam #2 to dam #3, dam #3 to dam #4 and dam #5 to dam #6 were good at estimating in all nine sections, but the error was a little bit high for small fishes. As a result, for two model sections, dam#1 to dam #2 plus dam #2 to dam #3 were the best in estimating. However, considering the investigating distance, dam #2 to dam #3 plus dam #5 to dam #6 were the most efficient model.
| Identifer | oai:union.ndltd.org:TW/103NTHU5112012 |
| Date | January 2015 |
| Creators | Chiou, Li Jiun, 邱立鈞 |
| Contributors | Tzeng, Chyng Shyan, 曾晴賢 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 75 |
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