博士 / 國立中興大學 / 生命科學系所 / 96 / The Formosan landlocked salmon (Oncorhynchus masou formosanus) has been on the endangered species list published by the government of Taiwan in 1984. It is an endangered endemic species and called the national treasure. A comprehensive conservation action plan for the Formosan landlocked salmon has been implemented by the Taiwanese government since 1986. IUCN - the World Conservation Union listed the salmon as being critically endangered in 1996. Shei-Pa National Park (NP) partially removed four dams from Gaoshan Stream – a tributary of Cijiawan Stream during 1999~2001 to promote conservation of the Formosan landlocked salmon. This attempt would serve as a milestone for many ecological conservation projects in Taiwan. However, the results of the action plan have not been as good as expected due to a lack of detailed quantitative analyses of fundamental and integrated population research results. The ultimate goal of this study is to provide an important conservation starting point for wildlife management decision-makers to protect the salmon based on scientific data and quantitative ecological theories. The relationship between the population dynamics of the Formosan landlocked salmon and the physical substrate (the width of the stream, water velocity, water depth, and substrate) of the fish habitats were evaluated by multivariate analysis after the partial removal of the four dams from Gaoshan Stream. The salmon population accordingly increased as the percentage of boulders increased by examining contour plots. Salmon may greatly benefit from maintaining boulders in these streams. Reductions in stream velocity and subsequent erosion benefit fish in riffle and step-pool habitats. Also, an increase in shelter space should lead to a reduction in mortality through predation that is typically observed in clear and shallow stream habitats. Boulders also reduce salmon energy expenditures for feeding and increase the probability of survival in the early stages. It appears that partial dam removal is an effective management approach for conserving the salmon population and maintaining the genetic heterogeneity in Kasha Stream. In order to analyze the dynamics of the population, Leslie and Latkovitch''s approach of constructing a stage-structure population matrix model was applied to predict population sizes of different stages for the following year based on census data of the previous year for the period 1996 to 2004. The derived population growth rates determined by the matrix models indicated that the Formosan salmon population is declining in Cijiawan Stream but has been increasing since 2001 in a tributary, Gaoshan Stream, after dams on that stream were partially removed. The least-squares solution method was applied to determine demographic parameters, including adult and subadult net fecundities, juvenile and subadult growth rates, subadult and adult survival rates, and the population growth rate according to 1996~2006 census data. The net fecundity of subadults (Fs) and Fa fluctuated more than did the survival and growth rates. The Gjs had a significantly higher elasticity than did the other demographic parameters, but the Gjs was relatively more stable than the Fs and Fa, which suggests that juveniles and net fecundities should be the focus of management efforts. The simulated results show that the population growth rate can exceed one if the Gjs and the survival rates of eggs-fry-juveniles which contribute to part of the net fecundity were slightly increase. The positive effect of dam removal will be significant. Therefore, further modification of the foundations of the dams in Gaoshan Stream should be conducted and evaluated in order to improve the flow of the stream. At the same time, the condition of the remaining dams in Cijiawan Stream should be meliorated, reducing the environmental flood impacts, remove human activities, planting vegetation widely to reduce the impacts of flood and increase the biomass of the fish''s food, utilize a more-ecologically oriented basis and analytical tools for long-term data to assess the extinction risk and minimum viable population of the endangered salmon, predict the salmon abundance and evaluate the patterns of habitat selection. This research offers more quantitative data and ecological pattern which can set up a reasonably communicated platform for the general public, ecologist and managers.
| Identifer | oai:union.ndltd.org:TW/096NCHU5105005 |
| Creators | Lii-Chang Chung, 鐘豊昌 |
| Contributors | Shao-Pin Yo, Hsing-Juh Lin, 尤少彬, 林幸助 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | en_US |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 105 |
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