Study On Fish Community And Resources In Jiulong River Estuary, Fujian

Jiulong River estuary is a mixture of seawater and freshwater intersection waters,affected by a variety of factors interaction and impact of regional, such as freshwater rivererosion and ocean tides, waves and currents, and so on. estuarine area affected by a complexphysical and chemical conditions and biological communities. It is a complex structure, theunique features of the ecosystem, Jiu-long Jiang estuary is an important fishing base forXia-men and Long-hai city, which with abundant fish resources. And the estuarine areas aredensely populated areas of human activity, its estuary area offers a variety of aquatic forsurrounding humans, and it played an important role in economic development for Xia-men,Zhang-zhou City.Therefore the study on fish community and resources of Jiu-long Jiangestuary has an important practical significance: the survey results on estuarine fish communityand resources provide advice for the utilization of fish resources in the Jiu-long Jiang estuary,and provide a reference for long-term study on the fishery resources of the Jiu-long Jiangestuary.In this study, based on the data acquired in month comprehensive surveys of the marineecosystem of the Jiulong River estuary in Sep.2010to Aug.2013consecutive36months,using a set-net and gill-net. The structures of fish community and resources in the JiulongRiver Estuary were studied including species compostion in different years, abundancevariety in different years, The fish community and resources in different years, The fishcommunity and resources of different waters.and spatio-temporal patterns.The study resultswill provide scientific evidence about the fisheries recruitment resource in the Jiulong RiverEstuary. The results are as follows:In this study, Jiulong River estuary in Sep.2010to Aug.2013, using a set-net and gill-net.According to Nelson classification system classification and identification, The resultsshowed: a total of247fish species were collected in this survey, belonging to2classes,19orders,82families and170genuses. Jiulong River estuary fish species are belongingto,Chondrichthyes and Actinopterygii classes,244fishes from the classes Actinopterygii(accounting for98.79%of the total species),3fishes from the classes Chondrichthyes(1.21%of the total species). And there were160fish species were warm water fishes,83fish species were warm temperature fishes and4fish species were cold temperature fishes,no fishspecies were cold water fishes. and1.62%cold temperature fishes. Therefore it can bedetermined that the sea have no fish species were cold temperature and cold water fishes.The fish assemblage of the Jiulong River Estuary was studied in Annual Ⅰ. A total of203fish species were collected in Annual Ⅰ, belonging to2classes,19orders,72families and136genuses. The fish assemblage of the Jiulong River Estuary was studied in Annual Ⅱ. Atotal of161fish species were collected in Annual Ⅱ, belonging to2classes,14orders,64families and119genuses. The fish assemblage of the Jiulong River Estuary was studied inAnnual Ⅲ. A total of171fish species were collected in Annual Ⅲ, belonging to2classes,16orders,57families and112genuses. Number of species of fish communities, biomass,number of individuals are higher in summer and autumn, the differences between the threeannual are obvious; less in winter and spring, the differences between the three annual are notobvious. And the dominant species included Clupanodon punctatus, Thryssa kammalensis,Odontamblyopus rubicundus, Ambassis gymnocephalus、Mudil affinis、Sardinella aurita、Anchoviell achinensis、Liza carinata and Clupanodon thrissa in Annual Ⅰ. the dominantspecies included Clupanodon punctatus, Mudil affinis、Ambassis gymnocephalus、Coiliagrayii, Anchoviell achinensis and Sardinella aurita in Annual Ⅱ. the dominant speciesincluded Clupanodon punctatus, Odontamblyopus rubicundus, Ambassis gymnocephalus、Mudil affinis、Stolephorus commersonii,Arius sinensis and Sardinella aurita in Annual Ⅲ.Jiulong River Estuary has a high diversity of fish communities, and diversity index changesoccur with the seasons, Comparing Annual Ⅰ and Ⅱ, Margalef D were decreased, Pielou J’and the diversity index H’ were increased in Annual Ⅱ; Comparing Annual Ⅰ and Ⅲ,Margalef D were decreased, Pielou J ’and the diversity index H’ were increased in Annual Ⅲ;Comparing Annual Ⅱ and Ⅲ, Margalef D、Pielou J ’and the diversity index H’ were increasedin Annual Ⅲ; Three years of Jiulong River estuary fish species diversity are at a high level, infavor of maintaining the stability of the fish community in the estuary.This paper studies the movements of fish resources in the Jiulong River Estuary situationconsecutive three years, and three years different salinity Island, Dao-mei site、Fu-gong siteand Zi-ni site fish resources changes in three sites were analyzed, studies show that for thethree years catch biomass, number of individuals, the density of fish resources showed adecreasing trend year by year, according to the subject of other studies have also found thatcatches consist essentially of age fish, young fish composition, these phenomena indicate theJiulong River Estuary fishery resources showing declining trend.Fishery catches andresources for different waters can be seen in the analysis of fish catch biomass density andindividuals and the resources are Fu-gong site, followed by the Dao-mei site, Zi-ni site at least, captured fish biomass、individuals and the resources density associated with different salinitygradients showed some variation, brackish areas, fresh water, salt water area catches the fishbiomass, the number of individuals and resource density was increasing trend.Aso by thisthird anniversary of the Jiulong River estuary area in Sep.2010to Aug.2013. The estuary ofthe dominant species of fish have Clupanodon punctatus （IRI=1227.27）、 Ambassisgymnocephalus （IRI=3168.14）、 Mudil affinis （IRI=1657.40）、 Sardinella zunasi（IRI=2828.91）、Anchoviell achinensis（IRI=1593.60）,Body length and weight compositionand resource utilization for analysis, the relationship between body weight and body length offish are showing the same kinds of fish in different periods and different growthcharacteristics of fish. The b value of Clupanodon punctatus is between2.9-3.1, shouldbelong to the type of constant growth, The Clupanodon punctatus resources has beenoverfished. The b value of Ambassis gymnocephalus is between2.9-3.1, should belong to thetype of constant growth, The Ambassis gymnocephalus resources has not been overfished.The b value of Mudil affinis is between2.9-3.1, should belong to the type of constant growth,The Mudil affinis resources has been overfished. The b value of Sardinella zunasi is greaterthan3.1, should belong to the type of positive constant growth, The Sardinella zunasiresources has been overfished. The b value of Anchoviell achinensis is smaller than2.9, shouldbelong to the type of negative constant growth, The Anchoviell achinensis resources has beenoverfished.A preliminary survey of the food relationship was carried out in the Jiulong RiverEstuary, Fujian during Sep.2010to Aug.2013consecutive60fish species.According to theirdietary habits, they may be divided into six types: planktivorous,benthophagous,nektivorous, planktivorous‐benthoph agous, planktivorous‐nektivorous, and benthophagous‐nektivorous. Based on the relationship among each nutrient class in foodweb, they may primarily bedivided into four nutrient classes:omnivores,lower carnivores,middle carnivores, highercarnivores. Most of them are the lower carnivores. Constitute a major food web is:phytoplankton�'zooplankton�'lower carnivorous fish�'Intermediate carnivorous fish�'Advanced carnivorous fish.