AB 17:269-283 (2012)  -  DOI: https://doi.org/10.3354/ab00481

Trophic model of the subtropical headwater stream habitat of Formosan landlocked salmon Oncorhynchus formosanus 

Hsing-Juh Lin1,2,*, Tsung-Ren Peng3, I-Chan Cheng1, Liang-Wei Chen3, Mei-Hwa Kuo4, Chyng-Shyan Tzeng5, Shang-Te Tsai6, Jeng-Tze Yang4, Sheng‑Hai Wu1, Yuan-Hsun Sun7, Shu-Fen Yu1, Shuh-Ji Kao

1Department of Life Sciences, 3Department of Soil and Environmental Sciences and 4Department of Entomology, National Chung Hsing University, Taichung 402, Taiwan
2Biodiversity Research Center and 8Research Center for Environmental Changes, Academia Sinica, Taipei 115, Taiwan
5Institute of Bioinformatics and Structural Biology, National Tsing Hua University, Hsinchu 300, Taiwan
6Department of Environmental Resources Management, TransWorld University, Yunlin 640, Taiwan
7Institute of Wildlife Conservation, National Pingtung University of Science and Technology, Pingtung 912, Taiwan

ABSTRACT: Using the Ecopath approach and a network analysis, a mass-balance trophic model was constructed to analyze the structure and energy flows of a high-altitude subtropical headwater stream, Chichiawan Stream, the only habitat of the Critically Endangered Formosan landlocked salmon Oncorhynchus formosanus. Natural abundances of carbon and nitrogen isotopes (δ13C and δ15N) were used as a complementary method to stomach content analysis to trace food sources of consumers in the stream. Riparian C3 plants were the major food source of dominant gatherer and filterer aquatic insects, while diatoms were the major food source of scraper aquatic insects. Lindeman trophic analysis indicated that the flows of detritivory and herbivory were quantitatively equally important as food sources for consumers in the stream, suggesting a close terrestrial−aquatic linkage. The trophic model of Chichiawan Stream comprised 13 compartments and 4 integer trophic levels with the highest trophic level of 3.12 for birds. The pedigree index for the trophic model was 0.71, indicating a high-quality model. The mixed trophic impacts indicated that the biomass of Formosan salmon was unlikely constrained by food sources or predation pressure by birds. In a comparative analysis with other trophic models of temperate mountain streams, the total consumer biomass and mean trophic transfer efficiency were relatively low in this subtropical mountain stream, which is characterized by high precipitation, steep channels, rapid current velocity, and changing flow regime. To conserve the Formosan salmon, the first priorities are agricultural runoff control and maintaining a well-vegetated riparian zone.

KEY WORDS: δ13C · δ15N · Chichiawan Stream · Riparian C3 plants · Diatoms · Ecopath · Network analysis

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Cite this article as: Lin HJ, Peng TR, Cheng IC, Chen LW and others (2012) Trophic model of the subtropical headwater stream habitat of Formosan landlocked salmon Oncorhynchus formosanus . Aquat Biol 17:269-283. https://doi.org/10.3354/ab00481

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