| Jingjiang section creates the waters with complicated state of flowing where fresh water and sea water come together, where the current of the lower reaches of the Yangtze River is met by that of the estuary under the influence of the current of the Yangtze River and the tides,and where many fishes breed, look for food and inhabit. Jingjiang section plays an important role in conserving fisheries resources .From January 1 in 2002,we set a stow net which with a height of 1.8 m and a length with 40 m in the coastal wetland of the Yangtze River at Xinqiao in Jingjiang(N31°56’,E120°01’). The professional fisherfolk would be appointed to collect fish after ebb-tide every day. The samples obtained on the 1st and 15th of each month during 2002-2003 and on the 1st , 11th and 21st during 2004-2009 were analyzed in the laboratory of Shanghai Ocean University.We study the temporal pattern of ecological character and species diversity of fish assemblage in Jingjiang section of the Yangtze River from 4 aspects :the fish fauna and compose ,species diversity , ecological character, the mass of 2th dominant species Pseudobtrama simony.1. From 2002 to 2009, there were 73 960 fish and total weight 409 256.23 g belonging to 237 batches of fish samples. There are 13 orders,26 families ,75 generas and 107 species. The species of Cypriniformes were the most, having 54 species accounting for 50.00%; the second was Perciformes and the third was Siluriformes. The species of Cyprinidae were the most, having 50 species. The fish fauna belongs to a transition between the lower reaches of the Yangtze River and estuarine fauna, and more verge on the lower reaches of the Yangtze River. From 2002 to 2009, the dominant species fish compositions was undiversified, higher during Summer and Autumn, lower during Spring and Winter. The subrogation rate of fish species in Years ranged from 13.85%-46.67%, the average rate was 33.93%, the rate between 2002 and 2009 was 40.70%, the same to say that 40% species have changed in 8 years.2. 237 samples from 2002 to 2009 were used to analyse the species diversity of fish assemblage in Jingjiang. Margalef’s index ranged from 6.21 to 8.13; Shannon-Weiner’s index ranged from 1.17 to 2.53; Pielou’s index ranged from 0.43 to 0.60; Simpson’s index ranged from 0.14 to 0.39; Whilm’s index ranged from 2.35 to 3.11. The indices analysis indicated that the species abundance and diversity level showed an increasing tendency while the dominant index was declining to some degree on the whole in fish assemblage of Jingjiang Section. Generally,the species abundance and diversity level were higher in Summer and Autumn but lower in Spring; the dominant index was higher in Spring but lower in Summer and Autumn.3. Fishes in the assemblage were divided into 14 types depending on different fishes ecological characters. The indices analysis indicated that sub-carnivores fish, bottom fish, small body-size fish and freshwater fish have species occupied dominant proportion in all the species numbers; polyphagia fish, surface fish, small body-size fish and freshwater fish have number and weight occupied dominant proportion in all the number and weight. We found that the fluctuation of individual number of polyphagia fish, surface water fish, small body-size fish and freshwater fish have the unltimate effect on the assemblage.4. 237 samples from 2002 to 2009 were used to analyse the temporal pattern and growth characteristics of Pseudobrama simony. Analysis indicated that monthly fish catch weight of P. simoni presented a Nonstationary Random Process. SPSS V13.0 software was used to construct the ARIMA model based on monthly fish catch data from January 2002 to December 2009 and ARIMA(1,0,0)(0,1,1)12 model included an equation of (1-0.387B)(1-B12)ln yt=(1-0.555B12)et. The fitting precision of ARIMA model was 83.21%-93.90% from 2003 to 2009. Meanwhile, the biomass peak of P. Simony appeared on May to September which was two or three months later than Hemiculter bleekeri, the first dominant species in the waters.The age and growth characteristics of the individual analysis for P. simoni Collected in 2005showed that males had three age groups from aged 1 to 3 and females only had two age groups from aged 1 to 2, significantly lower than the age structure of populations of Yao River and the Qiantang River . The Von bertalanffy growth equations of male were concluded as Lt=147.17×[1-e-0.1648×(t+3.2036)], Wt=44.36×[1-e-0.1648×(t+3.2036)]2.785. The estimated parameters for Logistic growth function were L∞(asymptote body length) =147.17 mm and W∞(asymptote body weight) = 147.17 g... |
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