Managing Water Level for Large Migratory Fish at the Poyang Lake Outlet: Implications Based on Habitat Suitability and Connectivity

Abstract

River–lake interaction is important for maintaining biodiversity, yet it is vulnerable to hydrological alteration. The connectivity of the channel connecting Poyang Lake and the Yangtze River not only ensures the regular migration of fish but also makes Poyang Lake a feeding and fattening ground for them. Unfortunately, human activities have dramatically changed the hydrodynamic conditions of Poyang Lake, which is experiencing severe drought due to the obvious decline in the water level in autumn and winter, especially since 2003. However, the possible impacts of the changes in the water level on the habitats of migratory fish remain unclear due to the limitation of traditional techniques in spatiotemporal analysis. Here, we combined a hydrodynamic model and habitat suitability model to simulate variations in the suitable habitat area and their connectivity under different water-level conditions. The conditions for the migration pathway of the target fish were obtained by a hydroacoustic survey using the Simrad EY60 echosounder. The results showed that the change in water level will significantly affect the spatiotemporal change in the suitable habitats and their connectivity. In particular, we found the existence of two thresholds that play a dominant role in illuminating the connectivity of effective suitable habitats (HC). Firstly, the maximum value of the weighted usable area (WUA) and HC can be achieved when the water level is more than 16 m. Secondly, when the water level is between 10 and 16 m, the changes in the HC are sensitive and rapid, and the area flooded at this stage is called the sensitive area. HC is a crucial element in fish migration and habitat conditions. Under the condition of continuous drought in the middle reaches of the Yangtze River, our research contributes to clarifying the influence of water level on key habitats for fish and optimizes the practice of river–lake ecological management.

The Classification of Riparian Habitats and Assessment of Fish-Spawning Habitat Suitability: A Case Study of the Three Gorges Reservoir, China

“…There are many studies on habitat utilization methods for constructing habitat suitability curves [47][48][49]. However, the proposed method is based on frequency distribution, which can be obtained from the habitat use of the target species in a specific life stage, without considering the availability of a given habitat type.…”

Hydroacoustic survey on fish spatial distribution in the early impoundment stage of Yuwanghe Reservoir in southwest China

“…The hydroacoustic data were converted and post-processed with Visual Analyzer version 4.3 software. Because the fish signals from the echosounder were scattered, the blind areas of detection and areas with high interference at 1 m below the level of the transducer and 0.5 m above the bottom of the probe were artificially eliminated; this step minimized the effect of noise (Li et al, 2022;Lian et al, 2022). The echograms of all survey sections were carefully examined and manually edited to regenerate the bottom surface if required.…”

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.…”

“…This led them to conclude that to improve efficiency and ensure safety, the triangular transect design with reliable coverage should be prioritized for hydroacoustic sampling in the Three Gorges Reservoir and similar canyonshaped reservoirs, especially when sampling at night. Li et al [3] in their paper "Managing water level for large migratory fish at the Poyang Lake outlet: implications based on habitat suitability and connectivity" used hydroacoustics to measure fish presence in the channel connecting Poyang Lake and the Yangtze River. Poyang Lake, the largest freshwater lake in China, holds great ecological value.…”