Influences of the Fish-Mouth Project and the Groins on the Flow and Sediment Ratio of the Yangtze River Waterway

A depth-integrated two-dimensional numerical model of current, salinity and sediment transport was proposed and calibrated by the observation data in the Yangtze River Estuary. It was then applied to investigate the flow and sediment ratio of the navigati

Using drift nets to capture early life stages and monitor spawning of the Yangtze River Chinese sturgeon (Acipenser 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.

Communities of gastrointestinal helminths of fish in historically connected habitats: habitat fragmentation effect in a carnivorous catfish Pelteobagrus fulvidraco from seven lakes in flood plain of the Yangtze River, China

Background: Habitat fragmentation may result in the reduction of diversity of parasite communities by affecting population size and dispersal pattern of species. In the flood plain of the Yangtze River in China, many lakes, which were once connected with the river, have become isolated since the 1950s from the river by the construction of dams and sluices, with many larger lakes subdivided into smaller ones by road embankments. These artificial barriers have inevitably obstructed the migration of fish between the river and lakes and also among lakes. In this study, the gastrointestinal helminth communities were investigated in a carnivorous fish, the yellowhead catfish Pelteobagrus fulvidraco, from two connected and five isolated lakes in the flood plain in order to detect the effect of lake fragmentation on the parasite communities. Results: A total of 11 species of helminths were recorded in the stomach and intestine of P. fulvidraco from seven lakes, including two lakes connected with the Yangtze River, i.e. Poyang and Dongting lakes, and five isolated lakes, i.e. Honghu, Liangzi, Tangxun, Niushan and Baoan lakes. Mean helminth individuals and diversity of helminth communities in Honghu and Dongting lakes was lower than in the other five lakes. The nematode Procamallanus fulvidraconis was the dominant species of communities in all the seven lakes. No significant difference in the Shannon-Wiener index was detected between connected lakes (0.48) and isolated lakes (0.50). The similarity of helminth communities between Niushan and Baoan lakes was the highest (0.6708), and the lowest was between Tangxun and Dongting lakes (0.1807). The similarity was low between Dongting and the other lakes, and the similarity decreased with the geographic distance among these lakes. The helminth community in one connected lake, Poyang Lake was clustered with isolated lakes, but the community in Dongting Lake was separated in the tree. Conclusion: The similarity in the helminth communities of this fish in the flood-plain lakes may be attributed to the historical connection of these habitats and to the completion of the life-cycles of this fish as well as the helminth species within the investigated habitats. The diversity and the digenean majority in the helminth communities can be related to the diet of this fish, and to the lacustrine and macrophytic characters of the habitats. The lake isolation from the river had little detectable effect on the helminth communities of the catfish in flood-plain lakes of the Yangtze River. The low similarities in helminth communities between the Dongting Lake and others may just be a reflection of its unique water environment and anthropogenic alterations or fragmentation in this lake.

Pseudobagrus fui Miao, a valid bagrid species from the Yangtze River drainage, South China (Teleostei: Bagridae)

Pseudobagrus fui Miao is a valid bagrid species that can be separated from all its congeners in having 27-33 anal-fin rays. Among the species of Pseudobagrus, it forms part of a group of approximately 20 species putatively characterized by having a smooth anterior margin of the pectoral-fin spine and short maxillary barbels not extending to the base of the pectoral-fin spine. Pseudobagrus fui, together with P. nitidus and P. vachelli, can be differentiated from all other fork-tailed species of this group by having no fewer than 20 branched anal-fin rays, the posterior end of the anal-fin base posterior to the vertical through the posterior end of the adipose-fin base, and anal-fin base longer than the adipose-fin base. It further differs from P. nitidus in having a gas bladder without beaded lateral and posterior margins, and from P. vachelli in having short maxillary barbels not extending to the base of the pectoral-fin spine. Pseudobagrus fui is currently known from the main stream of the upper Yangtze River and its tributaries, the Min River, Jialing River, Tuo River, Wu River and Chishui River in Sichuan Province, Guizhou Province, and the Chongqing City. The identity and nomenclature of Pseudobagrus nitidus is also discussed.

Trends of Superoxide Dismutase and Soluble Protein of Aquatic Plants in Lakes of Different Trophic Levels in the Middle and Lower Reaches of the Yangtze River, China

A limnological study was carried out to determine the responses of superoxide dismutase (SOD) activities and soluble protein (SP) contents of 11 common aquatic plants to eutrophication stress. Field investigation in 12 lakes in the middle and lower reaches of the Yangtze River was carried out from March to September 2004. Our results indicated that non-submersed (emergent and floating-leafed) plants and submersed plants showed different responses to eutrophication stress. Both SOD activities of the non-submersed and submersed plants were negatively correlated with their SP contents (P < 0.000 1). SP contents of non-submersed plants were significantly correlated with all nitrogen variables in the water (P < 0.05), whereas SP contents of submersed plants were only significantly correlated with carbon variables as well as ammonium and Secchi depth (SD) in water (P < 0.05). Only SOD activities of submersed plants were decreased with decline of SD in water (P < 0.001). Our results indicate that the decline of SOD activities of submersed plants were mainly caused by light limitation, this showed a coincidence with the decline of macrophytes in eutrophic lakes, which might imply that the antioxidant system of the submersed plants were impaired under eutrophication stress.

Abundance and conservation status of the Yangtze finless porpoise in the Yangtze River, China

middle and lower reaches of the Yangtze River, China. It is the only freshwater population of porpoises in the world and is currently listed as Endangered by IUCN. In November and December 2006 we used two boats and line transect methods to survey the entire current range of the population, except for two lakes (Poyang and Dongting). Sighting results were similar for both boats, so we pooled all data and analyzed them using two line transect models and a strip transect model. All models produced similar estimates of abundance (1111, 1225 and 1000). We then added independent estimates of the number of porpoises from the two lakes for a total estimate of approximately 1800 porpoises. Our findings indicate that the population continues to decline and that its distribution is becoming more fragmented. Our current estimate in the main river is slightly less than half the estimate from surveys between 1984 and 1991 (which was probably an underestimate). We also found an apparent gap in the distribution of porpoises between Yueyang and Shishou (similar to 150 km), where sightings had previously been common. Continued threats to Yangtze finless porpoises include bycatch in unregulated and unselective fishing, habitat degradation through dredging, pollution and noise, vessel strikes and water development. Immediate protective measures are urgently needed to ensure the persistence of finless porpoises in the Yangtze River. The survey design and analytical methods developed in this study might be appropriate for surveys of cetaceans in other river systems. (c) 2008 Elsevier Ltd. All rights reserved.

How polluted is the Yangtze River? Water quality downstream from the Three Gorges Dam

The concentrations of major anions and cations, nitrogen and phosphorus, dissolved and particulate trace elements, and organic pollutants were determined for the middle and lower reaches of the Yangtze River (Changjiang) from below the Three Gorges Dam (TGD) to the mouth at Shanghai in November 2006. The concentration of dissolved inorganic phosphate (DIP) was constant at a low level of 6-8 mu gP/L, but the concentration of nitrate (NO3-) approximately doubled downstream and was closely correlated with K+. This translated to a daily load of well over 1000 It of dissolved inorganic nitrogen (DIN) at Datong. The average concentrations of dissolved Pb (0.078 +/- 0.023 mu g/L), Cd (0.024 +/- 0.009 mu g/L), Cr(0.57 +/- 0.09 mu g/L), Cu (1.9 +/- 0.7 mu g/L), and Ni (0.50 +/- 0.49 mu g/L) were comparable with those in other major world rivers, while As (3.3 +/- 1.3 mu g/L) and Zn (1.5 +/- 0.6 mu g/L) were higher by factors of 5.5 and 2.5, respectively. The trace element contents of suspended particles of As (31 +/- 28 mu g/g), Pb (83 +/- 34 mu g/g), and Ni (52 +/- 16 mu g/g) were close to maximum concentrations recommended for rivers by the European Community (EC). The average concentrations of Cd (2.6 +/- 1.6 mu g/g), Cr (185 +/- 102 mu g/g), Cu (115 +/- 106 mu g/g), and Zn (500 +/- 300 mu g/g) exceeded the EC standards by a factor of two, and Hg (4.4 +/- 4.7 mu g/g) by a factor of 4 to 5. Locally occurring peak concentrations exceed these values up to fourfold, among them the notorious elements As, Hg, and Tl. All dissolved and particulate trace element concentrations were higher than estimates made twenty years ago [Zhang, J., Geochemistry of trace metals from Chinese river/estuary systems: an overview. Estuar Coast Shelf Sci 1995; 41: 631-658.]. The enormous loads of anthropogenic pollutants disposed to the river were diluted by the large water discharge of the Yangtze even during the lowest flow resulting in the relatively low concentration levels of trace elements and organic pollutants observed. We estimated loads of e.g. As, Pb and Ni to the East China Sea to be about 4600 kg As d(-1), 3000 kg Pb d(-1), and 2000 kg Ni d(-1). About 6000 t d(-1) of dissolved organic carbon (DOC) was delivered into the sea at the time of our cruise. We tested for 236 organic pollutants, and only the most infamous were found to be barely above detection limits. We estimated that the load of chlorinated compounds, aromatic hydrocarbons, phenols, and PAHs were between 500 and 3500 kg d(-1). We also detected eight herbicides entering the estuary with loads of 5-350 kg d(-1). The pollutant load, even when at low concentrations, are considerable and pose an increasing threat to the health of the East China Sea ecosystem. (c) 2008 Elsevier B.V. All rights reserved.

Population differentiation of Procypris rabaudi (Tchang) in the upper reaches of the Yangtze River revealed by mitochondrial DNA and RAPD markers

Procypris rabaudi (Tchang) is a cyprinid fish endermic to middle and upper reaches of the Yangtze River. Besides in main stream and large tributaries, there exists an early matured, small-sized ecological type in a small tributary, Tang River. In this study, mitochondrial DNA cytochrome h (cyt b) gene sequence analysis and randomly amplified polymorphic DNA (RAPD) analysis were performed to investigate the differentiation of the Tang River population from the Mudong reach population of the Yangtze River, with the purpose of conservation and exploitation of this fish. In the 1140 bps of cyt b gene sequence surveyed, 20 sites were found polymorphic, which defined 23 haplotypes. Among them, four haplotypes accounted for 54.4% of all individuals, while population-specific haplotypes occurred in low frequencies. Analysis of molecular variation on cyt b data revealed no significant partition existing between Tang River population and Mudong reach population. Analyses of 132 RAPD loci suggested that genetic variation between populations was significant, though values of different F-ST were not very high. The results revealed low genetic diversity and the beginning of population differentiation, suggesting that Tang River population should be designated as a separate Management Unit.

Field studies on the environmental factors in controlling microcystin production in the subtropical shallow lakes of the Yangtze River

Microcystin (MC) problem made more and more care about in China, intercellular MC (Int-MC) and cellular MC (Cel-MC) were important contents to reflect the producing-MC ability by cyanobacteria and by lakes. To study the correlations between Int-MC, Cel-MC concentration and biological and environmental factors, eight cyanobacterial blooming lakes were studied in the middle and lower reaches of the Yangtze River. Microcystin-RR (MC-RR) and Microcystin-LR (MC-LR) were the primary toxin variants in our data. From the linear correlations between MC and environmental factors, cellular-YR had significant correlation with most of chemical factors except total nitrogen (TN) and the ratio of total nitrogen and total phosphorus (TN/TP), most intracellular MC analogues had significant correlations with total dissolved nitrogen (TDN), ammonium (NH4+), nitrite (NO2-), TP, total dissolved phosphorus (TDP), Microcystis. From the canonal correspondence analysis, Int-MC concentrations were closely related with the chemical and biological factors, such as TP, total organic carbon (TOC), chlorophyll a (Chl a), Microcystis biomass, et al. While Cel-MC contents, especially Cel-RR and Cel-LR, were closely related with light environmental in the lakes such as water depth and transparence.

Stable isotope variations in particulate organic matter and a planktivorous fish in the Yangtze River

Temporal and spatial changes in delta(13) C and delta 15 N of particulate organic matter (POM) and Hemiculter leucisculus were studied in the Yangtze River of China. Isotopic signatures of POM showed seasonal variations, which was assumed to be associated with allochthonous organic input and autochthonous phytoplankton growth. delta C-13 of H. leucisculus was 1.1 % higher than that of POM, which suggested that the food source of H. leucisculus was mostly from the POM. A mass balance model indicated the trophic position of H. leucisculus in the food web of Yangtze River was estimated to be 2.0 - 2.1, indicating that this fish mainly feeds on planktonic organic matter, which agreed with previous gut content analysis.

Post-impoundment biomass and composition of phytoplankton in the Yangtze River

Damming, and thus alteration of stream flow, promotes higher phytoplankton populations and encourages algal blooms (density > 10(6) cells L-1) in the Three Gorges Reservoir (TGR). Phytoplankton composition and biomass were studied in the Yangtze River from March 2004 to May 2005. 107 taxa were identified. Diatoms were the dominant group, followed by Chlorophyta and Cyanobacteria. In the Yangtze River, algal abundance varied from 3.13 x 10(3) to 3.83 x 10(6) cells L-1, and algal biomass was in the range of 0.06 to 659 mg C m(-3). Levels of nitrogen, phosphorus and silica did not show consistent longitudinal changes along the river and were not correlated with phytoplankton parameters. Phytoplankton abundance was negatively correlated with main channel discharge (Spearman r = -1.000, P < 0.01). Phytoplankton abundance and biomass in the Yangtze River are mainly determined by the hydrological conditions rather than by nutrient concentrations.

The role of NH4+ toxicity in the decline of the submersed macrophyte Vallisneria natans in lakes of the Yangtze River basin, China

Experimental and field studies were conducted to evaluate the effects of NH4+ enrichment on growth and distribution of the submersed macrophyte, Vallisneria natans L, in lakes of the Yangtze River in China, based on the balance between free amino acids (FAA) and soluble carbohydrates (SC) in the plant tissue. Increase of NH4+ rather than NO3- concentrations in the water column caused FAA accumulation and SC depletion of the plant. The plant showed a unimodal pattern of biomass distribution along both FAA/SC ratios and external NH4+ concentrations, indicating that a moderate NH4-N concentration (< 0.3 mg L-1) benefited the plant, whereas the high NH4-N concentration (> 0.56 mg L-1) eliminated the plant completely. Therefore, 0.56 mg NH4-N mg L-1 in the water column was taken as the upper limit for V. natans in lakes of the Yangtze River basin. The mesocosm experiment showed that at a high external NH4-N (0.81 mg L-1), V. natans failed to propagate with a loss of half SC content (5 mg g(-1) DW) in the rhizomes, indicating that the consumption of carbohydrates for detoxification of excess NH4+ into non-toxic FAA significantly diminished carbohydrate supply to the rhizomes. This might consequently inhibit the vegetative reproduction of the plant, and also might be an important cause for the decline and disappearance of the plant with eutrophication. The present study for the first time reports substantial ecophysiological evidences for NH4+ stress to submersed macrophytes, and indicates that NH4+ toxicity arising from eutrophication probably plays a key role in the deterioration of submersed macrophytes like V. natans.