Artificial water-level fluctuation modulates trophic niches of benthic fish assemblages in one of the world's largest reservoirs

The impoundment of the Yangtze River and construction of the Three Gorges Dam and Reservoir created an unnatural flow regime with a 30 m water-level fluctuation and four artificial seasons that differ from the river's natural flow-regime timing. Using stable isotopes, we selected 15 common bent...

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Bibliographic Details
Published in:Canadian journal of fisheries and aquatic sciences 2023-12, Vol.80 (12), p.1921-1934
Main Authors: Liao, Chuansong, Wang, Jiacheng, Correa, Sandra Bibiana, Yu, Jixin, Yang, Rui, Yuan, Jing, Li, Wei, Ye, Shaowen, Guo, Chuanbo, Liu, Jiashou
Format: Article
Language:English
Subjects:
Canyons
Carbon 13
Fish
Flood control
Flood management
Guilds
Isotopes
Natural flow
Niche overlap
Niches
Reservoir construction
Rivers
Seasonal variations
Stable isotopes
Water level fluctuations
Water levels
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Summary:The impoundment of the Yangtze River and construction of the Three Gorges Dam and Reservoir created an unnatural flow regime with a 30 m water-level fluctuation and four artificial seasons that differ from the river's natural flow-regime timing. Using stable isotopes, we selected 15 common benthic fish species representing five trophic guilds to analyze seasonal variation in production sources, trophic niche width, and niche overlap. We hypothesized that, similarly to a natural flow regime, artificial hydrological seasons effectively influence fish trophic niches. We found consistency in seasonal shifts in the contribution of aquatic and terrestrial producers to fish biomass. δ 13 C and δ 15 N depicted seasonal changes in intra-guild trophic niche width and intra- and inter-guild niche overlap. Considering that the Three Gorges Reservoir's flow regime is artificially regulated, our findings suggest that water-level fluctuation is one of the key mechanisms driving such trophic shifts and allowing multiple species to coexist. Given the increased cascaded large reservoir construction and the concomitant creation of unnatural flow regimes in large rivers worldwide, these findings are timely. Our findings contribute to improving water-level management by optimizing rhythmicity while balancing flood control and fish protection.
ISSN:0706-652X
1205-7533
DOI:10.1139/cjfas-2023-0114