Spatiotemporal Distribution and Species Composition of Fish Assemblages in the Transitional Zone of the Three Gorges Reservoir, China

Pengcheng Lin,Myounghee Kang,Lin Chen,Xingchen Gao,Xin Gao,Chunling Wang

doi:10.3390/w12123514

Pengcheng Lin, Myounghee Kang + Show 4 more

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https://doi.org/10.3390/w12123514

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Abstract

The river–reservoir transitional zones play an important role in maintaining riverine fish biodiversity and abundance in highly regulated rivers. The Upper Yangtze River, which contains 286 fish species, is experiencing intense hydropower development. However, few studies have been conducted on the spatial distribution of fish in the river–reservoir transitional zones in the Upper Yangtze River, and it is therefore difficult to predict how this development will impact the region. In this study, a 200-kHz split-beam acoustic system in combination with biological samplings was used to investigate the composition and spatiotemporal distribution of the fish in the transition zone of the Three Gorges Reservoir (TGR) in 2017. The biological samplings comprised 7434 individuals from 61 species, 38 genera, 15 families, and 5 orders. The dominant fish species were Rhinogobio cylindricus, Coreius guichenoti, Hemiculter bleekeri, and Pelteobagrus vachelli. Acoustic detection identified the mean target strength (TS) to be −55.6 in May, −57.8 in August, and −55.8 dB in December. Accordingly, the average fish density was 4.96, 6.96, and 4.42 ind/1000 m3. Significant differences were found in the TS and fish density between flood season (August) and non-flood season (May and December). Spatially, fish preferred the meandering sections at 10–20 m deep. A size-dependent vertical distribution pattern was observed, with larger fish in the deeper layers and smaller fish in shallower waters. Lastly, our results suggest that meandering deep channels should be assigned high priority with respect to fish conservation in the Upper Yangtze River.

Highlights

Understanding the spatial distribution of fish is a major theme in freshwater ecology
Most studies have focused on the fish distribution at the reservoir or larger watershed scales, whereas little attention has been paid to the reach or local scales [8]
The Mudong reach has ecological functions that are important for the Upper Yangtze fisheries; in particular, it serves as a spawning ground for four major species of Chinese carp and a nursery area for a number of native the Three Gorges Dam (TGD), and has maintained a natural flowing regime during the flooding season (May to September)

Summary

Introduction

Understanding the spatial distribution of fish is a major theme in freshwater ecology. Past studies of freshwater fish in streams and rivers have led to a generalized understanding that freshwater fish assemblages are structured in part by local channel structure and hydraulic conditions in temperate regions [2,3,4]. A fundamental property of fish habitats, affects stream metabolism, and fish bioenergetics, and can structure fish communities. Anthropogenic activities, such as the construction of huge dams and changes in land use, can alter channel morphology and affect the temporal distribution of thermally-suitable habitats [4]. Most studies have focused on the fish distribution at the reservoir or larger watershed scales, whereas little attention has been paid to the reach or local scales [8]

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