Wei Qiwei

Hydrological Status of the spawning ground of Acipenser sinensis underneath the Gezhouba Dam and its relationship with the spawning runs

Abstract The spawning runs of Chinese Sturgeon (CS; Acipenser sinensis) were observed 37 times below Gezhouba Dam of Yangtze River between 1983 and 2004. Five hydrological factors (water temperature, water level, flow discharge, silt content and current velocity) were monitored on a daily basis at the spawning ground between October and November for 22 consecutive years (1983–2004). The effect of current velocity on the spawning ground at the bottom layer of the river, where CS was spawning for four years, was measured (1996–1999). The authors of this study analyzed the relationship between the five hydrological factors and the respective spawning runs. Twenty-two years of continuous observations indicated that the daily mean values of all the five hydrological factors fluctuated within a certain range when CS was spawning. It was concluded that the optimal values for the hydrological factors during the spawning runs are 18.0–20.0°C for temperature, 14100 m3/s for discharge volume, 42.0–45.0 m for water level above the sea level, and 0.2–0.3 kg/m3 for silt content in the water, wherein the current velocity above the bottom layer to stimulate the fish to spawn should be between 1.0–1.7 m/s. The optimal water temperature might provide an essential precondition for other factors to trigger spawning. As water temperature reaches the optimal values and most of the other parameters are at the brink of deviation from their optimal range of values (water level, current velocity and silt content in the water), CS would begin to spawn. By 2009, when the Yangtze Three Gorges Project, which is located 45 km upstream of the Gezhouba Dam, is completed and begins to operate normally, changes in the downstream water temperature are expected to occur, which may have a negative effect on the development of gonad and the stimulation of spawning of CS; however, the anticipated decrease of the silt content in the water may be considered favorable for the performance of the spawning site.

Design of Vibrio 16S rRNA Gene Specific Primers and Their Application in the Analysis of Seawater Vibrio Community

The pathogenic species of genusVibrio cause vibriosis, one of the most prevalent diseases of maricultured animals and seafood consumers. Monitoring their kinetics in the chain of seafood production, processing and consumption is of great importance for food and mariculture safety. In order to enrichVibrio-representing 16S ribosomal RNA gene (rDNA) fragments and identify these bacteria further real-timely and synchronously among bacterial flora in the chain, a pair of primers that selectively amplifyVibrio 16S rDNA fragments were designed with their specificities and coverage testified in the analysis of seawaterVibrio community. The specificities and coverage of two primers, VF169 and VR744, were determined theoretically among bacterial 16S rDNAs available in GenBank by using BLAST program and practically by amplifying,Vibrio 16S rDNA fragments from seawater DNA. More than 88.3% of sequences in GenBank, which showed identical matches with VR744, belong toVibrio genus. A total of 33 clones were randomly selected and sequenced. All of the sequences showed their highest similarities to and clustered around those of diverse knownVibrio species. The primers designed are capable of retrieving a wide range ofVibrio 16S rDNA fragments specifically among bacterial flora in seawater, the most important natural environment of seafood cultivation.

Early ontogenesis of Brachymystax lenok tsinlingensis

Sexually mature Brachymystax lenok tsinlingensis were caught from the wild and,after artificial fertili-zation,embryonic and larval development were investigated.Larvae of mean body length(9.64 ± 1.03) mm hatched 408 h after fertilization.The total accumulated temperature of embryonic development was 193.35℃·d at a water temperature of 9.31-12.80 ℃.We defined six broad stages of embryogenesis(zygote,cleavage stage,blastula stage,gastrula stage,neurula stage,and organ formation stage),which included 26 minor periods.The hatching larvae had a transparent body with clearly visible sarcomeres,but with limited swimming capability.Five days after hatching,a patch of melanin appeared on the body surface.The yolk sac began to disappear 12 days after hatching and parr markings started to appear after 46 days,at which stage the fins of the larvae resembled those of young fish.The morphological characteristics of the embryos and larvae are described and the factors affecting ontogenesis of the early life stages of Brachymystax lenok tsinlingensis,including water temperature,dissolved oxygen and water quality,are discussed.