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Vol. 47 No. 1, 2008
Relationship between the Formosan Landlocked Salmon Oncorhynchus masou formosanus Population and the
Physical Substrate of Its Habitat after Partial Dam Removal from
Kaoshan Stream, Taiwan
Lii-Chang
Chung1, Hsing-Juh Lin1,*, Shao-Pin Yo1,
Chyng-Shyan Tzeng2, Chao-Hsien Yeh3, and
Cheng-Hsiung Yang2
1Department
of Life Sciences, National Chung Hsing University, Taichung 402, Taiwan
2Institute of Bioinformatics and Structural Biology,
and Department of Life Science, National Tsing Hua University, Hsinchu
300, Taiwan
3Department of Water Resources Engineering, Feng Chia
University, Taichung 407, Taiwan
Lii-Chang
Chung, Hsing-Juh Lin, Shao-Pin Yo, Chyng-Shyan Tzeng, Chao-Hsien Yeh,
and ChengHsiung Yang (2008) In order to protect and restore the
population of the Formosan landlocked salmon (Oncorhynchus masou formosanus,
Jordan and Oshima) (Salmoidae), an endemic and endangered species of
the central Taiwanese highlands, Shei-Pa National Park partially
removed 4 dams from Kaoshan Stream during 1999-2001. The purpose of
this study was to evaluate the relationship between the abundance of
the Formosan landlocked salmon and the physical substrate of its
habitat as a consequence of habitat modifications caused by partial
removal of the dams from Kaoshan Stream. After removal of the dams,
fish were able to freely travel up and down the stream, but the
relative slope of the riverbank became steeper, and the velocity of the
river increased leading to more-serious erosion than was found prior to
dam removal. We applied a principal component analysis (PCA) method to
determine the most significant factors affecting the fish population.
The 1st principal component of the fish population explained 79% of the
total salmon population variance. The 1st 2 principal components of
substrate rock size explained 72% of the total substrate variance. By
examining a contour plot, we found that when the percentage of boulders
was higher, the salmon population accordingly increased. Moreover, poor
breeding years that highly impact the salmon population appeared to be
a result of flooding caused by typhoons during the breeding season from
late Oct. to Dec. Following flooding, it appears that the river
substrate had a higher percentage of boulders, which possibly benefited
the salmon population. Consequently, partial dam removal may have
improved the survival rate of the salmon population in response to
floods.
Key words: Boulders, Principal component
analysis, Contour plot, Floods, Breeding season.
*Correspondence: Tel: 886-4-22840416. Fax:
886-4-22874740. E-mail:hjlin@dragon.nchu.edu.tw
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