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

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.

Dam‐induced difference of fish habitat distribution in the fluctuating backwater zone of the Three Gorges Dam

“…The ecological investigation suggested that 29.6% of the total area of spawning sites of the four major Chinese carp (FMCC), including Mylopharyngodon piceus , Ctenopharyngodon idella , Hypophthalmichthys molitrix and Hypophthalmichthys nobilis in the backwater zone of TGD was submerged, resulting in a sharp decline in the spawning size of FMCC after dam impoundment (Tang et al, 2022). Most of the previous work has focused on alterations in the composition of aquatic fauna, such as the fish community (Gao et al, 2010; Lin et al, 2020; Liu et al, 2012) and the plankton community (Lu et al, 2018), as well as community composition of benthic fauna, right after the impoundment (Lu et al, 2018). However, fish habitat distribution in the post‐dam period is still poorly understood.…”

Meander reshaping – the formation process of a wintering riverbed depression of fish

“…With the permanent erosion-accumulative processes in the channel of the Lower Irtysh, one can observe the formation or loss of wintering riverbed depressions of fish, which in turn justifies the need for continuous monitoring of the riverbed depressions. Moreover, the study of movements and spatial distribution of animals provides new information on the distribution of populations of a species in critical habitats, which is useful for its protection among other reasons (Ecclestone et al, 2020;Lin et al, 2020;Moore et al, 2020;Sutton et al, 2021;Withers et al, 2021).…”

Hydroacoustics in Marine, Transitional and Freshwaters

“…In this Special Issue, the published papers were mainly related to applications of hydroacoustics in fisheries research and aquatic ecology, with some also addressing technical problems and monitoring. Papers related to fisheries acoustics dominated the submissions and covered all types of aquatic environments: rivers (Yangtze River [1][2][3], Pearl River [4], and River Thames [5]), lagoon channels (Ingril and Prévost channels [6]), natural lakes (Lake Poyang [3], Lake Stechlin [7], and Lake Dejguny [8]), artificial reservoirs (Three Gorges Reservoir [1,2]), and the sea (Mediterranean Sea [9], and South China Sea [10]). Three of the papers were related to the Yangtze River basin.…”

“…To protect and restore aquatic resources, a 10-year fishing ban for all aquatic biota in the Yangtze River has been implemented since 2017. Due to the limitations of traditional research methods like net sampling, Lin et al [1] aimed to demonstrate the feasibility of hydroacoustic techniques, which could be successfully used to quantify the fish density and spatial distributions in the upper Yangtze River. They used acoustics in combination with biological samplings to investigate the composition and spatiotemporal distribution of fish in the transition zone of the Three Gorges Reservoir (TGR).…”