River-lake Connectivity Research Articles

The spatial pattern of larval fish assemblages in the lower reach of the Yangtze River: potential influences of river–lake connectivity and tidal intrusion

Landscape pattern plays an important role in structuring of larval fish assemblages in large river basins. The lower reach of the Yangtze River includes the river section from the mouth of Poyang Lake, the largest freshwater lake in China, downward to the estuary. We hypothesized that river-lake connectivity at the upstream portion and tidal intrusion at the downstream portion are significant drivers of larval fish assemblages. Larval fish were collected monthly from April 2012 through September 2013 in three locations at Anqing (AQ), Nanjing (NJ), and Jingjiang (JJ). Fifty-six taxa of larval fish were identified with 52 of them determined of species. Larval fish were highly abundant from April through August; the number of species and the abundance were much higher at AQ than at NJ and JJ; the bloom of larval fish at JJ tended to be later than at NJ and AQ. We suggest that the larger number of species and higher abundance of larval fish at AQ reflect the effects of the connectivity of Poyang Lake with the river upstream of AQ, and the delayed bloom of larval fish and the occurrence of estuarine species at JJ reflect the influences of tidal intrusion from the estuary.

Water Pollutant Control for a River-Lake Region to the Northwest of Lake Taihu

In this paper, Zhushan Bay watershed to the northwest of Lake Taihu was selected as the research area. Taking the developed river-lake connectivity and frequent exchange of pollutants into consideration, we put forward a calculation method of water environment carrying capacity (WECC) for river network based on multiple objectives of water quality reaching standard in river environment function zones and control sections, concentration profile constraint of sewage outlet. According to the proposed method, we calculated the watershed WECC, assigned to each control unit, and quantitatively analyzed the reductions and reduction rate of pollutants under the condition of total amount of each pollutant of control unit reach water quality standards. The results showed that: The pollution loads of each pollutant in Zhushan Bay watershed were greater than WECC. The reduction of COD, NH3-N, TN and TP is 834.4 tons, 226.1 tons, 724.8 tons and 108.9 tons, and the reduction rate of COD, NH3-N, TN and TP is 13.8%, 36.5%, 55.2% and 73.4%, respectively. This paper plays a guiding role in the research of total amount control of river network in Zhushan Bay watershed, and provides important references for total amount control of similar river-lake region.

Ecological influence of dam construction and river-lake connectivity on migration fish habitat in the Yangtze River basin, China

Habitat fragment owning to obstruct of dams and barriers badly affect the aquatic faunas. Many spawning sites of migration fishes are lost, and their growth and reproduction are affected. The Yangtze River with connected lakes is the most important fresh water fishery area in China. The Yangtze's four major carp species (YFMCS) are the most typical migration fish lived in this area. They reproduce in river and grow in lake. Distributaries lies between the Yangtze River and Dongting Lake are the passages for these migration fishes. Due to the construction of dams and barriers, some original passages were out of use. Up to now, only four channels exist between the river and lake, there are Songcikou, Taipingkou and Ouchikou normally called “three outlets”, and Chenglingji inlet. Diverted Water Volume (DWV) and the Percentage of Diverted Water (PDW) through the three outlets reflect the relationship between the Yangtze River and the Dongting Lake.The variation of river-lake relation caused by dam construction, and the effect on migration fishes are discussed in this paper. The relationship of DWV and fry output in middle reach of the Yangtze river and the Dongting Lake, PDW and the percentage of the YFMCS in a total catch of fish, DWV and flux of carp fry at the Jianli station, DWV and yield of the YFMCS were analyzed. The results show that dams and barriers constructed on the Yangtze River threaten some fish species in this area, especially the migration fishes. The connectivity degree of river and lake decide the growth and reproduction of emigration fishes, the yield of the YFMCS increase by the DWV increase, and hydraulic project have important influence on reproduction of fishes. In order to reduce the ecological influence of hydropower projects, reservoir management especially in spawning season should integrate ecological demand.

Influence of connectivity on Cladocera diversity in oxbow lakes in the Taquari River floodplain (MS, Brazil)

Aim: The aim of this study was evaluate the influence of river-lake connectivity on Cladocera diversity; Methods: Sampling of macrophyte stands of three oxbow lakes were carried out between August/04 and September/06 every two months; Results: A total of 49 Cladocera species were identified. Three are new records for the state. The Chydoridae family was the most representative, with 34 species. In lakes 1 and 2, Chydoridae and Macrothricidae were the most abundant taxa, while Chydoridae and Daphniidae were the most representative groups in lake 3. Abundance and species richness tended to be greater in lakes 1 and 2; Conclusions: In the oxbow lakes, the environmental variations conditioned by annual dry and rainfall cycles favored a greater diversity of Cladocera, since a greater connectivity with the Taquari River produces constant disturbances that are detrimental to the diversity of this group.