The Research Of The Temporal Pattern Of Fish Assemblage In Coastal Jingjiang Section Of The Yangtze River Over Last Decade

The Yangtze Estuary is one of the most important estuaries inecological service functions of the Western Pacific Region, with anabundance diversity and fishery resources. Jingjiang section of the YangtzeRiver near the estuary area with unique ecosystem conditions and variety ofhabitats, the provincial aquatic germplasm resources conservation areawhich is the provincial aquatic species resource protection area and thenational aquatic species resource protection area of Eriocheir sinensis andSiniperca chuatsi. Jingjiang section plays an important role in conservingfisheries resources of the Yangtze River.From January1in2002, we set a stow net in the coastal wetland ofJingjiang Section of the Yangtze River and collected samples for10years.We study the temporal pattern of ecological character and species diversityof fish assemblage in Jingjiang section of the Yangtze River from5aspects:the fish fauna and compose, species diversity, abundance and biomass,relationship between fish assemblage and some ecological factors. 1. From2002to2011, there were14orders,28families,77generasand113species. The species of Cypriniformes were the most, having59species from3families,36generas and accounting for52.21%; the secondwas Perciformes including,10families,16generas and21species andaccounting for17.70%. The species of Cyprinidae were the most, having52species. The fish fauna belongs to a transition between the lower reachesof the Yangtze River and estuarine fauna. From2002to2011, the annualaverage Jaccard similarity index was62.96%, and the highest Jaccardsimilarity index was up to79.49%between2008and2009with the lowestbetween2005and2010was51.25%. The first dominant specie wasHemiculter bleekeri.2. Over last decade, the Margalef’s index monthly ranged from1.17to6.16with Shannon-Weiner’s index from0.64to2.89, Whilm’s index from0.75to2.81, Pielou’s index from0.24to0.87. Generally,the speciesabundance, diversity and evenness level were higher in Summer andAutumn but lower in Spring and showed an increasing trendency.3. The MIW of entire fish assemblage was only5.65±1.13g and theMIW of fish assemblage in autumn was7.15±1.56g, significantly higherthan the other seasons.. The average MIW of the dominant speciesincluding Hemiculter bleekeri.and so on was4.71±0.99g with7.59±1.81g of the common species. Average MIW of the dominant species wassignificantly less than the average MIW of common species and the entire assemblage.4. ABC curve analysis showed that the number advantages curve hasbeen in the top of the weight dominance curve over last decade, indicatingthat the small fish and juvenile fish was the advantaged groups of theassemblage structure. And the two curves significantly close to each otherin2010and2011, indicating that larger body of fish added to the ranks ofdominant species, and the assemblage structure changed. The timecorrelation analysis showed that the annual change of fish assemblage innumber and weight was not significant.5. The variation of ecological factors including precipitation, thehighest water level, tidal range, water temperatures, turbidity, COD,duration of sunshine, atmospheric pressure and ammonia during2007-2009and its correlation analysis with fish assemblage showed that fishassemblage of species richness, sample weight, MIW was a significantpositive correlation with the highest water level, water temperature,turbidity, but significant negative correlation with atmospheric pressure.Larger individual fishes like Pseudobrama simoni, Coilia nasus,Ctenopharyngodon idella, Parabramis pekinensis, Cultrichthyserythropterus, Pelteobagrus vachellii and Cynoglossus gracilis showed asignificant positive correlation with water temperature and water level, buta significant negative correlation between smaller individual fishes likeAbbotina rivularis, Pseudorasbora parva and water temperature, water level.