scholarly journals The Non-stationary Environmental Effects on Spawning Habitat of Fish in Estuaries: A Case Study of Coilia mystus in the Yangtze Estuary

2021 ◽  
Vol 8 ◽  
Author(s):  
Dong Wang ◽  
Rong Wan ◽  
Zengguang Li ◽  
Junbo Zhang ◽  
Xiangyu Long ◽  
...  
Keyword(s):  
Habitat Selection ◽  
Saltwater Intrusion ◽  
Yangtze Estuary ◽  
Sea Surface ◽  
Spawning Habitat ◽  
The South ◽  
The Yangtze Estuary ◽  
Commercial Fish ◽  
Coilia Mystus ◽  
Gwr Model

The estuarine areas provide necessary spawning habitat, nursing habitat, and migratory for a variety of fishes and the environmental conditions are of significant heterogeneity. Coilia mystus is the key commercial fish that spawns in the Yangtze Estuary and the yield has declined sharply in the past 30 years. In order to understand the spawning habitat selection mechanism of C. mystus, the geographically weighted regression (GWR) model was applied to explore the non-stationary effect of environmental variables [e.g., the sea surface temperature (SST) and the sea surface salinity (SSS)] and geographical variables [e.g., the distance to the coast (DTC) and the depth (DEP) of water] on the egg density distribution of C. mystus. The data were derived from the spring and summer ichthyoplankton surveys carried out from 2019 to 2020 in the Yangtze Estuary, China. The GWR model results showed that the key variables in different seasons had spatial non-stationary effects on the distribution of spawning habitat of C. mystus, which were mainly caused by regional rise in temperature and saltwater intrusion of the South Branch. In the spring, the SSS, the DTC, and the DEP were the main impact factors and saltwater intrusion in the South Branch might lead to the trend that the spawning habitat moved further upstream to the Changxing Island. The SST was most important in the summer and the relatively lower SST was more crucial in the spawning habitat selection than the DTC and the DEP. The GWR model performed well in the study of C. mystus potential spawning habitat in the Yangtze Estuary. We recommend that more attention should be paid in regional variation of environmental factors to explore fish potential spawning habitat in the estuarine areas.

Wind Effect on the Saltwater Intrusion in the Yangtze Estuary

2020 ◽  
Vol 105 (sp1) ◽  
Author(s):  
Zhengjin Tao ◽  
Ao Chu ◽  
Yongping Chen ◽  
Shiqiang Lu ◽  
Biao Wang
Keyword(s):  
Saltwater Intrusion ◽  
Yangtze Estuary ◽  
Wind Effect ◽  
The Yangtze Estuary

scholarly journals THE BRANCHING CHANNEL NETWORK IN THE YANGTZE ESTUARY

2012 ◽  
Vol 1 (33) ◽  
pp. 69
Author(s):  
Zheng Bing Wang ◽  
Pingxing Ding
Keyword(s):  
Yangtze Estuary ◽  
River Delta ◽  
Sediment Supply ◽  
Channel Structure ◽  
The South ◽  
Channel Network ◽  
The Yangtze Estuary ◽  
The North ◽  
Navigation Channel ◽  
The Impact

The channels in the Yangtze Estuary have an ordered-branching structure: The estuary is first divided by the Chongming Island into the North Branch and the South Branch. Then the South Branch is divided into the North Channel and South Channel by the Islands Changxing and Hengsha. The South Channel is again divided into the North and South Passage by the Jiuduansha Shoal. This three-level bifurcation and four-outlet configuration appears to be a natural character of the estuary, also in the past (Chen et al., 1982), although the whole system has been extending into the East China Sea in the southeast direction due to the abundant sediment supply from the Yangtze River. Recently, the natural development of the system seems to be substantially disturbed by human interferences, especially the Deep Navigation Channel Project. For the understanding of the behaviour of the bifurcating channel system in the estuary we present analysis on two aspects: (1) the equilibrium configuration of river delta distributary networks, and (2) influence of tidal flow on the morphological equilibrium of rivers. Based on the analyses we conclude that the branching channel structure of the Yangtze Estuary can be classified as tide-influenced river delta distributary networks. Its basic structure is the same as in case of river dominated delta. The empirical relations describing the basic features of the river-dominated distributary delta networks can be explained by theoretical analysis, although they are not fully satisfied by the Yangtze Estuary because of the influence of the tide. Two major influences of the tide are identified, viz. increasing the resistance to the river flow into the sea and increasing the sediment transport capacity. As consequence of these two influences the cross-sectional area of the river/estuary increases in the seawards direction and the bed slope decreases. The insights from the analyses are helpful for the understanding of the impact of the Deep Navigation Channel Project on the large scale morphological development of the estuary.

scholarly journals Spring Ichthyoplankton Assemblage Structure in the Yangtze Estuary Under Environmental Factors

2021 ◽  
Vol 8 ◽  
Author(s):  
Yibang Wang ◽  
Cui Liang ◽  
Zhaomin Chen ◽  
Shude Liu ◽  
Hui Zhang ◽  
...  
Keyword(s):  
Dominant Species ◽  
Large Scale ◽  
Yangtze Estuary ◽  
Assemblage Structure ◽  
The Yangtze Estuary ◽  
Larimichthys Polyactis ◽  
Factors Affecting ◽  
Coilia Mystus ◽  
Trachidermus Fasciatus ◽  
Fish Spawning

Estuaries, where fresh and salty water converge, provide abundant nutrients for ichthyoplankton. Ichthyoplankton, including fish eggs, larvae, and juveniles, are important fishery recruitment resources. The Yangtze Estuary and its adjacent waters comprise a typical large-scale estuary and supply many important fish spawning, feeding, and breeding areas. In this study, 1,291 ichthyoplankton individuals were collected in the Yangtze Estuary in spring, from 2013 to 2020. The aims of the study were to provide detailed information on characteristics of the ichthyoplankton assemblage, explore interannual variation, and evaluate the effects of environmental variables on the temporal variation in assemblage structure. Twenty-six species in seventeen families were identified. The dominant species were Coilia mystus, Chelidonichthys spinosus, Engraulis japonicus, Hypoatherina valenciennei, Larimichthys polyactis, Salanx ariakensis, Stolephorus commersonnii, and Trachidermus fasciatus. The ichthyoplankton assemblage changed significantly over time, and Chelidonichthys spinosus became one of the dominant species. Canonical correspondence analysis showed that temperature and chlorophyll a were the key factors affecting the assemblage structure in the Yangtze Estuary in spring.

Salt intrusion in an estuarine network, a study with an exploratory model

2020 ◽  
Author(s):  
Huib E. de Swart ◽  
Inge van Tongeren
Keyword(s):  
River Water ◽  
Fresh Water ◽  
River Discharge ◽  
Yangtze Estuary ◽  
Strong Impact ◽  
The South ◽  
The Yangtze Estuary ◽  
Salt Intrusion ◽  
The North ◽  
Averaged Model

<p>Many estuarine systems experience increased salt intrusion, which is harmful for ecology and agriculture and may cause problems for fresh water supply to cities. Some causes of salt intrusion are extraction of fresh water in the upper reaches of the estuary and climate change. Besides, anthropogenic measures, like deepening of channels, are known to have a strong impact on the salt balance.</p><p>This contribution focuses on salt intrusion in estuarine networks, which consist of multiple connected channels. The motivation of the study arose from observations in the Yangtze estuary that reveal frequent overspill of salt between its different channels. To understand the underlying physics of such behaviour, an exploratory, width- and tidally averaged model has been developed and analysed. This model describes the competition between export of salt by river flow and import of salt by density-driven flow and horizontal diffusion. Its key new aspect is that it generalises an earlier model MacCready (2004) from a single channel to estuarine networks. The new model calculates the distribution of salt in, and salt exchange between the channels, as well as the distribution of river water over the different channels.  </p><p>Here, results will be presented for a simplified estuarine network consisting of the South Channel, South Passage and North Passage of the Yangtze Estuary. It will be shown that, for the present-day situation, dry season and spring tide, salt intrusion is larger in the South Passage than in the North Passage. As will be explained, this is mainly due to the different geometry of the two channels. Furthermore, it will be shown that there is slightly more river water transport through the South Passage than through the North Passage, except during high river discharge and neap tide. These results agree with field data and results from numerical studies.</p><p>Other results that will be presented are the sensitivity of salinity intrusion length and distribution of river water over the different channels to changes in, respectively, upstream river discharge, tidal currents and human interventions. Specifically, the effects of the creation of a Deepwater Navigation Channel in the North Passage on salt dynamics will be shown and discussed.</p><p>Reference:<br>MacCready, P. 2004. Toward a unified theory of tidally-averaged estuarine salinity structure. Estuaries 27, 561-570.</p>

Reproductive biology of Coilia mystus (Linnaeus) from the Yangtze Estuary, China: responses to overexploitation

2011 ◽  
Vol 27 (5) ◽  
pp. 1197-1202 ◽  
Author(s):  
W.-P. He ◽  
Y.-X. Li ◽  
M. Liu ◽  
K. V. Radhakrishnan ◽  
Z.-J. Li ◽  
...  
Keyword(s):  
Reproductive Biology ◽  
Yangtze Estuary ◽  
The Yangtze Estuary ◽  
Coilia Mystus

Retrieval and Analysis on the Sediment Concentration of the South Branch of the Yangtze Estuary Based on TM

2013 ◽  
Vol 353-356 ◽  
pp. 2763-2768 ◽  
Author(s):  
Jia Ling Hao ◽  
Tong Cao ◽  
Zhu Jun Zhang ◽  
Li Ping Yin
Keyword(s):  
Remote Sensing ◽  
Suspended Sediment ◽  
Suspended Sediment Concentration ◽  
Sediment Concentration ◽  
Yangtze Estuary ◽  
The South ◽  
The Yangtze Estuary ◽  
Remote Sensing Technology ◽  
Sensing Technology ◽  
Quantitative Remote Sensing

Suspended sediment concentration is important index of water quality, and assessment coefficient of water environment. Remote sensing technology can overcome the shortcomings of conventional methods, such as low speed, long period, and scarce temporal and spatial data distribution. Thus it is meaningful to introduce remote sensing technology to monitoring suspended sediment. In this paper, two TM/ETM+ images of the Yangtze estuary were utilized, and based on review of available domestic and overseas remote sensing data of suspended sediment, also combined with analysis on the 21 samples of synchronizing collection on April 28, 2009 and 3 samples of synchronizing collection on March 26, 2000 at the same time of satellite passing through respectively, the inversion model of satellite quantitative data was setup correlated to suspended sediment concentration. Then the classification diagram of sediment concentration in the surface water at the South Branch of the Yangtze Estuary was drawn. This study gets the following conclusions:(1) TM4 band reflection coefficient is more related to surface sediment concentration, the correlation coefficient is 0.884. (2)Through the regression analysis, the quantitative remote sensing model is established. By the mode, using satellite picture, sediment concentration distribution map in study area is obtained. (3)The diffusion law of suspended sediment, the range of high turbid water region and the estuarine sediment transportation were further discussed from monitoring data, and its characteristic phenomenon were observed and the cause was also explained.

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