Spatial distribution and habitat suitability indices for non-spawning and spawning adult Chinese sturgeons below Gezhouba Dam, Yangtze River: Effects of river alterations

Abstract

Summary The study objectives were to identify the horizontal and vertical distributions of adult Chinese sturgeon (Acipenser sinensis) in relation to the Habitat Suitability Index (HSI) in order to assess the utility of the only remaining spawning grounds by adults and to understand the effects of river alterations on habitat use. Twenty‐five adults were surgically implanted with ultrasonic transmitters and located by mobile tracking and fixed monitoring stations during the 2006–2009 spawning seasons. Fish locations and depths along with water depth and bottom characteristics (topography, velocity, and embeddedness) were measured during tracking and used to determine HSI curves for non‐spawning and spawning adults. Most fish locations (91%) were on the spawning grounds (GZD to Miaozui reaches). Horizontal distribution differed before and after spawning, among years, and between the sexes. Adults used deeper depths during the day than at night (P < 0.001), while also preferring shallower depths on the day of spawning rather than the days before and after. Mature females used deeper water than other females (P < 0.001). Comparison of horizontal and vertical distributions before and after river alterations found fewer adults using the grounds impacted by a diversion dike which was built on the spawning grounds. Adults also used shallower depths after the Three Gorges Dam regulated river flow over the spawning grounds. The HSI model and the use of Weighed Usable Areas (WUA) for mature and immature adults indicated suitable habitat was available, but was reduced by the river alterations resulting in reduced spawning success and placing the population into a situation close to extirpation.

Migrations and movements of adult Chinese sturgeon Acipenser sinensis in the Yangtze River, China

“…The impounding of the reservoir at TGD in 2003 has greatly changed the natural river hydrological rhythm. These changes probably influence spawning movements and success of A. sinensis (Wang et al , in press).…”

Spatiotemporal Distribution and Assemblages of Fishes below the Lowermost Dam in Protected Reach in the Yangtze River Main Stream: Implications for River Management

“…Fish habitat is an essential component of ecosystem [23], while studies of fish habitats downstream Gezhouba Dam were merely limited to the habitats of large endangered individual Chinese sturgeon ( Acipenser sinensis Gray) [24–27]. This study covers different reaches with different geography characteristics that are habitats of various fish species.…”

Spatial distribution and spawning stock estimates for adult Chinese sturgeon (Acipenser sinensis Gray, 1835) around the only remaining spawning ground during the trial operation of the newly constructed Three Gorges Project in the Yangtze River, China

“…During the 2004–2008 spawning seasons, capture trials of A. sinensis using setlines were made immediately below the Gezhouba Dam, parallel to ultrasonic telemetry and while monitoring the gonadal development (Yang et al., ; Wang et al., , ). Most were released back into the river after marking (ultrasonic and/or anchor tags).…”

“…The only remaining spawning area is located just below the Gezhouba Dam (Zhang et al., ). Most adults aggregate here and in adjacent areas (a total stretch of about 30 km) for pre‐spawning holding (Wang et al., , ). The first study on the number of adults aggregating below the dam was conducted in 1983–1984 (Ke et al., ), when the total number was estimated to be around 2180 adults.…”