Studies On Diversity, Age And Growth Of Fishes In Sublakes Of Poyang Lake National Nature Reserve, Jiangxi China

Autumn fishery by enclosing plate-shaped sublake is an extensive fishingmethod around the Poyang Lake, which is influenced by the hydrological changes andhas a certain negative impact on fishery resources. In order to research thecomposition and characteristic dynamics of fish community in the sublake, andobserve the correlation between the cath and water level changes and the age structureand growth characteristics of the main commercial fishes, providing scientific basisfor the management of natural reserve, an investigation was carried out for three timesin Dahuchi and Shahu located in Poyang Lake National Nature Reserve, Jiangxiprovince, China, from2011to2013. The study was conducted in aspect of water levelchanges, species diversity and age structure to describe the ture situation and its changfeatures and probable problems. The connection time of Dahuchi and Shahu with XiuRiver in2011were23days and10days respectively, and a phenomenon ofdrought-flood abrupt alternation occurred in Poyang Lake. Poyang Lake had a floodyear in2012, and the connection time of Dahuchi and Shahu with Xiu River were124days and108days respectively. While Poyang Lake suffered a drought year again in2013, and both lakes did not connected with the river.7times inquiries wereimplemented in two lakes in2011,9times in2012and5times in2013. The mainresults of the investigation study were as follows:(1) In2011, totally41fish species were collected, belonging to6orders,10families and34genera, and38species in Dahuchi, belonging to6orders,10familiesand31genera, and32species in Shahu, belonging to6orders,7families and27genera, six of them were commercial fishes. In2012, totally49fish species werecollected, belonging to6orders,10families,35genera, and44species in Dahuchi,belonging to6orders,10families,32genera, and36species in Shahu, belonging to6orders,8families,27genera, eight of them were commercial fishes. In2013, totally38fish species were collected in Dahuchi, belonging to6orders,10families,32genera, seven of them were commercial fishes, and there was no fisheries productionin Shahu because of the low water level.(2) The fishes in Dahuchi and Shahu had three kinds of diet-herbivores,carnivores and omnivores, the fishes of carnivores and omnivores were predominant,but the fishes of herbivores were much less. The habitats also had three kinds-middleup of water layer, middle down of water layer and benthos, and the type of middle down had most species. The reproduction place can be divided into6kinds-both riverand lake, river, upper reaches of river, middle and upper reaches of river, lake, stream,which was predominant in the type of both river and lake, and the reproduction timeof most fishes were spring and summer.(3) The analysis of non-metrimultidimensional scaling (MDS) showed thatcommunity diversity varied along years and sites, reflecting five discrete colonies.Likewise, the results of Shannon-Wiener diversity index, Pielou evenness index andRichness index showed that there were certain difference for the fish communitybetween different years and sites.(4) The results of relative importance index revealed that the dominant species ofmain commercial fishes were Ctenopharyngodon idellus and Cyprinus carpio inDahuchi in2011, and that of small fishes were Hemiculter bleekeri, Carassiusauratus and Belligobio nummifer. In Shahu in2011, the dominant species of maincommercial fishes were Ctenopharyngodon idellus and Cyprinus carpio, and forsmall fishes were Carassius auratus, Pseudobrama simoni and Sarcocheilichthyskiangsiensis. In2012, the dominant species of main commercial fishes wereElopichthys bambusa and Hypophthalmichthys molitrix in Dahuchi, and that of smallfishes were Gnathopogon argentatus, Hemiculter bleekeri and Hyporhamphusintermedius. But in Shahu the dominant species of main commercial fishes wereHypophthalmichthys molitrix and Cyprinus carpio, its dominant species of smallfishes were Hyporhamphus intermedius, Hemiculter bleekeri and Coiliabrachygnathus. Futhermore, in2013and the dominant species of main commercialfishes were Parabramis pekinensis and Siniperca kneri in Dahuchi, and its dominantspecies of small fishes were Hemiculter bleekeri, Pseudobrama simoni andSaurogobio dabryi. The correlation analysis indicated that there were positivecorrelation between CPUE a day and the water level in the year of2011, while suchcorrelation declined in the year of2012and2013.(5) Elopichthys bambusa had5age groups, amount of age1and1+werepredominant. Parabramis pekinensis had6age groups, mainly of the individuals ofage2+. Ctenopharyngodon idellus had5age groups and was predominant in age1+and2. Erythroculter ilishaeformis had6age groups, the individuals of age3and4were the most. Hypophthalmichthys molitrix had4age groups with a homogeneousdistribution in the age of0+,1and1+for most of them.(6) The body length and body weigth of Elopichthys bambusa, Parabramis pekinensis, Ctenopharyngodon idellus, Erythroculter ilishaeformis andHypophthalmichthys molitrix had a relation of power function. The results of bodycondition index demonstrated that the obesity degree of Elopichthys bambusa andErythroculter ilishaeformis were relative lower, but higher in Ctenopharyngodonidellus and Parabramis pekinensis, and Hypophthalmichthys molitrix was betweenthem.The catch from the same lake in species composition was basic unanimouslyfrom2011to2013, and the largest group of fish community was from Cypriniformes,but the dominant species of commercial fishes and small fishes remarkably changed.The population quantity decreased obviously, and fish community distincted fromeach other.The yield of catch had a downward trend, having a status of low age andsmall size, but its relation with water level changes was ambuguous.