Short‐Term Distribution Patterns of Young‐of‐the‐Year Fish Assemblages between the Main Stem and Affiliated Lakes in the Middle Reaches of the Yangtze River, China

Abstract

Survival of fish in the first year is critical in determining the year‐class strength of fish populations. In river–floodplain ecosystems, affiliated lakes (i.e., floodplain lakes that are hydrologically connected to the river) play a crucial role as nursery habitats for young‐of‐the‐year (age‐0) fish. However, most lakes in the river–floodplain ecosystem of the Yangtze River, China, have been disconnected. Data on age‐0 fish distribution are important for developing appropriate strategies for management and conservation of fish populations in the river. We investigated the distribution patterns of age‐0 fish in the middle reaches of the Yangtze River. Overall, 33 species were collected from four main‐stem reaches (29 species) and two lakes (32 species) connected with the main stem from July to September in 2010 and 2011. The CPUE and species richness of age‐0 fish were higher in the lakes; age‐0 species richness showed an increasing trend in a downstream direction along the main stem. Analysis of similarities revealed that significant differences in assemblage structure of age‐0 fish occurred mainly among sampling sites. The higher CPUE and species richness of age‐0 fish in the lakes indicate the importance of connected lakes as age‐0 fish nursery habitats. We also found abundant age‐0 fish in the main stem and a relationship between spatial patterns of age‐0 fish with site proximity to the Three Gorges Dam, similar to previously observed spatial patterns in larval fishes. These results indicate the importance of the main stem as age‐0 fish nursery habitat and the effects of the dam on age‐0 fish distribution. This study presents the first data on age‐0 fish in the Yangtze River, thus providing a baseline for future age‐0 fish research. It also provides essential information for management and conservation measures, such as restoring the lateral connectivity between the main stem and disconnected lakes and guidelines for ecological operation of the dam.

Shoreline hardening affects species composition and condition of larval fishes in the Yangtze River: Implications for conservation and inshore habitat restoration

“…Since the 1950s, due to embankments and flood gates, most lakes, except the two largest ones, Dongtong Lake and Poyang Lake, have lost their lateral connectivity with the main channel (Liu & Wang, 2010). As a result, at present, only inshore habitats located in the main stem are available as nurseries for the fish larvae, which loss most of habitats in affiliated lakes (Cheng et al, 2021). Importantly, these inshore river habitats have also been severely degraded by bank revetments for flood control and navigation security; more than 50% of the shorelines are now hardened to some degree (Xie, 2020).…”

“…Since the 1950s, due to embankments and flood gates, most lakes, except the two largest ones, Dongtong Lake and Poyang Lake, have lost their lateral connectivity with the main channel (Liu & Wang, 2010). As a result, at present, only inshore habitats located in the main stem are available as nurseries for the fish larvae, which loss most of habitats in affiliated lakes (Cheng et al, 2021).…”