Response of Fish Assemblages to Habitat Changes and Fishing Activity in a Tributary of the Jinsha River in Southwest China

Abstract

Reservoir impoundment affects fish habitat condition, in turn likely influencing the spatial and temporal distribution patterns of fish assemblage structure in the impounded area. Fishing activity and instream gravel and sand mining are important anthropogenic factors, and flow discharge, water temperature, and precipitation are important natural environmental variables; both anthropogenic and natural factors likely have impacted fish assemblage structure in impounded and unimpounded waterbodies. We used multivariate analysis to evaluate the combined effects of two adjacent reservoir impoundments in the main stem of a large river (Jinsha River; the upper segments of the Yangtze River), overfishing, instream gravel and sand mining, the natural flow regime, and other environmental variables (water temperature and precipitation) on fish assemblage structure in the Heishui River, a small, free‐flowing tributary upstream of the mainstream reservoirs. Fish assemblage data and abiotic data collected over 10 years (2008, 2010, and 2011–2017) were analyzed. The results showed that fish assemblages of the Heishui River temporally clustered into two groups that were strongly associated with the two downstream cascade reservoirs (Xiangjiaba and Xiluodu reservoirs) in the main‐stem Jinsha River. The relationships between fish assemblage structure and abiotic factors were tested using a distance‐based linear model and were visualized using distance‐based redundancy analysis, showing that the main factors explaining the interannual and seasonal variation in fish assemblage structure were instream gravel and sand mining, mainstream reservoir impoundment, and seasonal flow regime. Among these, instream gravel and sand mining in this tributary played the most significant role in affecting the temporal variation of fish assemblage structure and explained 34.12% of the total variability. Mainstream reservoir impoundment and seasonal flow regime exerted secondary effects on the temporal variation of fish assemblage structure and together explained 13.39% (7.00% and 6.39%, respectively) of the total variability. This study suggests that the relevant administrative agencies should focus more on free‐flowing habitat maintenance in this tributary and the control of instream gravel and sand mining.

Fish Community Structure and Biomass Particle-Size Spectrum in the Upper Reaches of the Jinsha River (China)

“…In addition, hydropower cascade development contributes to the main causes of species diversity and community structure changes. Since the implementation of the Jinsha River upstream cascade, the river flow rate dropped significantly, and the decrease in water reduced the river-wetted perimeter area, water flow velocity change, and channel depth; additionally, the dissolved oxygen and habitat changes resulted in reduced fish survival in the reservoir area [ 4 , 5 ]. In this study, we found that the temporal and spatial distributions of Schizothoracinae were positively correlated with flow velocity and dissolved oxygen, and there was more biomass and larger particle-size classes in tributaries with higher flow velocity and dissolved oxygen.…”

“…However, with rapid economic development and hydropower development, the environmental pollution of water bodies is aggravated, leading to habitat fragmentation, spatiotemporal changes in runoff distribution, increased disturbance of the natural habitat environment of fish, and serious threats to river ecosystems. In addition to overfishing, fish resources and diversity in the upper reaches of the Jinsha River have shown a declining trend [ 3 , 4 , 5 ].…”

“…The construction of cascade power stations in the upper reaches of the Jinsha River will lead to habitat barriers and fragmentation, shrinkage of flowing water habitats, and changes in the natural hydrological situation [ 10 ]. The tail of the main stream reservoir, the local waters of tributaries in the reservoir area, and even the mouth of tributaries will become important areas for fish to reproduce and inhabit [ 3 , 4 ]. Based on this, this research used survey data from 2019 to 2020 for fish and the environment, analysed the fish diversity status upstream of the Jinsha River, and built a fish biomass particle-size spectrum for the main stream and tributaries.…”

Impacts of Sand Mining Activities on the Wetland Ecosystem of Poyang Lake (China)

“…Sand mining can reshape river terrain, alter fish habitats, destroy benthic animal habitats and fish spawning grounds, and is one of the main drivers of freshwater wetland ecosystem degradation and biodiversity decline in the basin [4][5][6][7]. Ecological problems caused by irregular sand mining exist in river basins around the world, such as the Chalakudy, Periyar, and Muvattupuzha river basins in India, the shrinkage of Tonlé Sap Lake in Southeast Asia, and the degradation of fish habitats in California River basin in the United States [8][9][10].…”