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Summary A 95-day experiment was conducted to evaluate the performance of a visible implant elastomer tag (VIE) versus a coded wire tag (CWT) implanted in juvenile Tibet fish Oxygymnocypris stewartii (Lloyd, 1908; total length 5~7 cm) under laboratory conditions. Mortality, tag retention and growth in three groups of juvenile O. stewartii (VIE-tagged, CWT-tagged and control) in duplicate were determined in six indoor tanks (300-L/tank volume, 100 fish/tank) at 15.6 ± 0.5°C water temperature. Results showed that neither tagging method had a significant difference on the mortality of the experimental fish, but that the growth rate in the VIE group was significantly lower than in the CWT and control groups. Mean tag retention in the VIE group was 95.2%, and 98.9% in the CWT group, with no significant differences in tag retention in the two methods. The study indicates that both VIE and CWT are suitable short-term tagging methods for hatchery O. stewartii juveniles.

Summary Eight hydroacoustic surveys were conducted between 2007 and 2010 to determine the spatial distribution and habitat choice of adult Chinese sturgeon (Acipenser sinensis) within 85 km immediately downstream of Gezhouba Dam, which is the lower-most dam blocking upstream sturgeon migration in the Yangtze River. A potential 32 A. sinensis were identified; depth, velocity, etc., characteristics were determined at the sturgeon site with an Acoustic Doppler Current Profiler. Most targets (26 individuals, 81.3%) were in water >12 m deep, and most (29 individuals, 90.6%) targets were near the river bottom. All targets stayed in or were close to the river channel (distance to the thalweg about one tenth of the river width). Fish were primarily distributed among four separate and deep areas. Variations in the water level played no significant role in fish distribution. Large, deep areas attracted the most fish. A preliminary analysis of environmental factors including water depth, flow velocity, Froude number and Reynolds number indicated that the bedform morphology (deep areas) was probably the key factor determining the A. sinensis habitat preference. Future conservation of the sturgeon will be more effective when special attention is given to the four refuges.

Summary The food preferences of paddlefish (Polyodon spathula) in polyculture with bighead carp (Aristichthys nobilis) are unknown. Three consecutive analyses of gastrointestinal contents of paddlefish and bighead carp were conducted at 3d, 11d and 19d after introduction into the non-fed ponds. The objectives of this study were to test for competitive interactions between bighead carp and paddlefish, and to document their preferred prey when the two species have a limited food resource. The results showed that paddlefish and bighead carp are basically competitive in their diets. When they were cultured in one pond at the same density, paddlefish fed more quickly and efficiently, depleting the food resources for bighead carp; however, bighead carp were able to switch and trap small food items with the decrease in available food resources. Moreover, larger zooplankton abundance declined in ponds after fish were introduced.

Summary The effects of stocking density (15, 30, 45, and 60 fish m−2) on the production economics, growth, food utilization, and body composition of Amur sturgeon reared in cages were investigated. The weight of the fish at the start of trial was 48.7–51.6 g. After 75 days of rearing, the mean weights were 110.3 ± 11.2, 90.3 ± 10.2, 79.9 ± 8.5, 78.7 ± 7.2 g in the aforementioned densities, respectively. The results show that the growth performances in the various treatments differed significantly (P

Summary This study was performed to determine the spatial structure and bottom characteristics of the only remaining spawning area of Chinese sturgeon (Acipenser sinensis) located just downstream of the Gezhouba Dam. During the period 1996–2003, three methods were employed, including (i) the examination of the stomachs of opportunistic predatory fishes that feed on sturgeon eggs, (ii) tracking the mature sturgeons by ultrasonic tags and (iii) capturing eggs and yolk-sac larvae (ELS) at and near the river bottom by D-shaped bottom drift nets to monitor the spawning activities of A. sinensis. It was found that A. sinensis selected permanent locations to mate. There were two mating locations: an upstream mating area (UMA), in the tailrace of the Dajiang Hydroelectric Station and about 870 m far from the Gezhouba Dam (area, 0.1 km2), and a downstream mating area (DMA), about 2500 m from Gezhouba Dam (area, 0.3 km2). The DMA was the chief mating area and was used every year. The incubation area (for dispersal of fertilized eggs to incubate) was range from 870 m to 7 km from the dam. Generally, the total length of the spawning area was 5–7 km length (area 2.0–2.7 km2) with the range slightly varied in different spawning activities. A relief map of the riverbed and a bottom hydroacoustic survey of the DMA found a deep depression and rocky substrate. These may be important characteristics of geomorphology for the spawning area of A. sinensis.

P>A sampling system for capturing sturgeon eggs using a D-shaped bottom anchored drift net was used to capture early life stages (ELS) of Chinese sturgeon, Acipenser sinensis, and monitor annual spawning success at Yichang on the Yangtze River, 1996-2004, before and just after the Three Gorges Dam began operation. Captured were 96 875 ELS (early life stages: eggs, yolk-sac larvae = eleuthero embryos, and larvae); most were eggs and only 2477 were yolk-sac larvae. Most ELS were captured in the main river channel and inside the bend at the Yichang spawning reach. Yolk-sac larvae were captured for a maximum of 3 days after hatching began, indicating quick dispersal downstream. The back-calculated day of egg fertilization over the eight years indicated a maximum spawning window of 23 days (20 October-10 November). Spawning in all years was restricted temporally, occurred mostly at night and during one or two spawning periods, each lasting several days. The brief temporal spawning window may reduce egg predation by opportunistic predators by flooding the river bottom with millions of eggs. During 1996-2002, the percentage of fertilized eggs in an annual 20-egg sample was between 63.5 to 94.1%; however, in 2003 the percentage fertilized was only 23.8%. This sudden decline may be related to the altered environmental conditions at Yichang caused by operation of the Three Gorges Dam. Further studies are needed to monitor spawning and changes in egg fertilization in this threatened population.

The authors reviewed the aquacultural history of Acipenseriformes in China, related the legal status and examined the current status of the cultured species or hybrids, origins of seedlings, quantities of production, geographic distribution in farming, and the sustainability for both restocking programmes and human consumption. The census shows that since 2000, the production of cultured sturgeons in China appears to have become the largest in the world. As of 2000, the rapid growth of sturgeon farming in China mainly for commercial purposes has shifted harvests in the Amur River from caviar production to the artificial culture of sturgeon seedlings. This dramatic development has also caused a series of extant and potential problems, including insufficient market availability and the impact of exotic sturgeons on indigenous sturgeon species. Annual preservation of sufficient higher-age sturgeons should be a national priority in order to establish a sustainable sturgeon-culture industry and to preserve a gene pool of critically endangered sturgeon species to prevent their extinction.

Summary This study provides the first report of length–weight relationships (LWRs) for Pseudogyrinocheilus prochilus (Sauvage & Dabry de Thiersant, 1874) and Jinshaia sinensis (Sauvage & Dabry de Thiersant, 1874) collected from the middle reaches of the Jinsha River, southwest China. Samples were obtained between June 2005 and November 2006. A total of 491 specimens belonging to two fish species were analyzed. LWRs were W = 0.0170L2.970 (r2 = 0.980) for P. prochilus and W = 0.0194L2.849 (r2 = 0.977) for J. sinensis. Prior to this study, the LWRs for P. prochilus were unknown. In addition, new maximum size for J. sinensis was provided.

Summary This study provides the first report of length–weight relationships (LWRs) for six endemic fish species collected from the Zengqu River and the Ouqu River, two of the tributaries to the upper reaches of the Jinsha River, southwest China. Samples were obtained in May 2013 and September 2013 using various types of fishing gear. A total of 413 specimens belonging to six fish species were analyzed; their LWRs were W = 0.0069L3.086 (r2 = 0.987) for Schizothorax wangchiachii (Fang, 1936), W = 0.0076L3.029 (r2 = 0.980) for Schizothorax dolichonema (Herzenstein, 1889), W = 0.0029L3.315 (r2 = 0.961) for Schizopygopsis malacanthus (Herzenstein, 1891), W = 0.0082L 2.970 (r2 = 0.950) for Ptychobarbus kaznakovi (Nikolsky, 1903), W = 0.0017L3.464 (r2 = 0.957) for Triplophysa stolioczkae (Steindachner, 1866), and W = 0.0037L 3.190 (r2 = 0.956) for Triplophysa orientalis (Herzenstein, 1888). Prior to this study, the LWRs for S. dolichonema, P. kaznakovi and T. orientalis were unknown. In addition, new maximum sizes for four of the species are provided.