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Summary: This study determined the length–weight relationships (LWRs) and length–length relationships (LLRs) of seven freshwater fish from the Daning River, a tributary of the Yangtze River, southwest China. Specimens were collected between July 2016 and July 2017 using drift gill nets (mesh size 1, 2 and 3 cm), cage net (0.5 cm mesh size) and electroshock fishing techniques quaterly. Parameter b values of LWRs ranged from 2.647 to 3.276 (r2 > .963) and b values of LLRs ranged from 1.091 to 1.213(r2 > .985). Six new LLRs and seven new maximum length data are presented. The biometric data and their relationships are relevant to Fishers science to supplement other data sets needed for fisheries management. [ABSTRACT FROM AUTHOR]

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 km), and a downstream mating area (DMA), about 2500 m from Gezhouba Dam (area, 0.3 km). 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 km) 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. [ABSTRACT FROM AUTHOR]

Based on the five wild Chinese sturgeons which were captured from the Yichang section of the Yangtze River, and the 323 offsprings of the Chinese sturgeons, were studied as to their survival, development and behaviour under aquarium conditions between 2005 and 2007 in the captive environment of an aquarium. All five wild caught females survived, with weight gains ranging from 0.55% (Specimen W1#: Onset: 320.00 kg, Final: 336.00 kg; across 27 months) to 10.00% of original body weight (Specimen W32#: Onset: 125.00 kg, Final: 175.00 kg; across 4 months). In addition, the gonads of one captured fish redeveloped to stage IV by August 2007. The changes of the depth in the tank were observed before, during and after active food intake. Furthermore, the fish formed strong feeding associations with live food items, such as Hypophthalmichthys molitrix, Cyprinus carpio, and Paralichthys lethostigma, while rarely feeding on Hexagrammos otakii and Epinephelus awoara, occasionally on Monopterus albus, Penaeus vannamei, Leiocassis longirostris, and never on Eriocheir sinensis H. Milne-Edwards, Misgurnus anguillicaudatus, Silurus asotus Linnaeus, Octopus variabilis, Anadara uropygimelana. The development of food preferences in the captive environment suggest that these Chinese sturgeon successfully acclimated to the large aquarium, in addition, the survival rate of the filial generation offspring was 86%. Across the study period, for the older captive bred offspring (1997 and 2001 stocks) minimum weight increase per month was 4.28% (F1-2001: Onset: 12.24 ± 1.11 kg, Final: 25.35 ± 2.10 kg; over 25 months) and the minimum lengthwise growth rate per month was 1.39% (F1-1997: Onset: 187.32 ± 1.32 cm, Final: 260.00 cm; across 28 months). However, the youngest sturgeon (the 2005 offspring), had the highest weight gain of 29.35% per month (Onset: 16.50 ± 1.92 kg, Final: 8733.33 ± 739.80 kg; across 18 months) and lengthwise growth rate 35.70% per month (Onset: 15.53 ± 0.77 cm, Final: 115.33 ± 4.14 cm; across 18 months) respectively. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The swimbladder of fishes is readily compressed by hydrostatic pressure with depth, causing changes in buoyancy. While modern fishes can regulate buoyancy by secreting gases from the blood into the swimbladder, primitive fishes, such as sturgeons, lack this secretion mechanism and rely entirely on air gulped at the surface to inflate the swimbladder. Therefore, sturgeons may experience changes in buoyancy that will affect their behavior at different depths. To test this prediction, we attached data loggers to seven free-ranging Chinese sturgeons Acipenser sinensis in the Yangtze River, China, to monitor their depth utilization, tail-beating activity, swim speed and body inclination. Two distinct, individual-specific, behavioral patterns were observed. Four fish swam at shallow depths (7–31 m), at speeds of 0.5–0.6 m s−1, with ascending and descending movements of 1.0–2.4 m in amplitude. They beat their tails continuously, indicating that their buoyancy was close to neutral with their inflated swimbladders. In addition, their occasional visits to the surface suggest that they gulped air to inflate their swimbladders. The other three fish spent most of their time (88–94%) on the river bottom at a depth of 106–122 m with minimum activity. They occasionally swam upwards at speeds of 0.6–0.8 m s−1 with intense tailbeats before gliding back passively to the bottom, in a manner similar to fishes that lack a swimbladder. Their bladders were probably collapsed by hydrostatic pressure, resulting in negative buoyancy. We conclude that Chinese sturgeons behave according to their buoyancy, which varies with depth due to hydrostatic compression of the swimbladder. [ABSTRACT FROM AUTHOR]

In this study, the facilities and techniques of fingerling production for the Chinese Sturgeon (Acipencer sinesis) cultivation as practiced in the hatchery of the Yangtze River Fisheries Research Institute are described. Initiation of feeding in larvae, adaptation of young fish to formulated feeds, water temperature control, and maintaining other water quality parameters within limits as well as disease control techniques were the key factors affecting the survival rate and growth performance of young Chinese Sturgeons. The suitable range of water temperatures for fingerling rearing is considered to be between 18 and 22. The feed conversion rate when using formulated turtle-feed at 70 days post-hatch was 0.45 while that of specific sturgeon-feed was 0.67. Under our experimental conditions, SGR (Specific Growth Rate) of the young Chinese sturgeon was 8.15% day-1, 7.71% day-1 and 6.96% day-1 in the years 2000, 2001 and 2003, respectively. Fingerlings of 10-15 cm total length were produced in our facilities and were at that time ready for release into the natural Chinese Sturgeon habitats. Disease control still is a major problem requiring more intensive research. [ABSTRACT FROM AUTHOR]

This study determined the length-weight relationships of three freshwater fish species [ Culter oxycephaloides (Kreyenberg & Pappenheim, 1908), Squalidus argentatus (Sauvage & Dabry de Thiersant, 1874), Rhodeus sinensis (Günther, 1868)] from Pengxi River, a tributariy of Yangtze River of China. Fish were collected during 2016 using drift gill nets (mesh size 1, 2 and 3 cm) and cage net (0.5 cm mesh size). For Culter oxycephaloides had no previous length-weight estimates were reported in the science literature. For Squalidus argentatus the present estimate includes a new maximum total length while for Rhodeus sinensis our study confirms the only existing LWR estimate quite well. [ABSTRACT FROM AUTHOR]