Study On Fish Community Ecology In Jiulong River Estuary

In this study, based on the data acquired in monthly surveys of the marine ecosystem of theJiulong River estuary from Sep.2010to Aug.2012, using a set-net and gill-net. The structures offish community in the Jiulong River Estuary were studied including species compostion,abundance variety, community diversity and spatio-temporal patterns. The study results willprovide scientific evidence to evaluating river ecosystem and the fisheries resource in the JiulongRiver Estuary. The results were as follows:First, the spatial structure and seasonal changes of estuarine fish assemblages in the JiulongRiver Estuary Estuary were analysed based on twelve months comprehensive surveys conductedfrom Sep.2010to Aug.2012.The results showed: a total of234fish species were collected in thissurvey, belonging to2classes,19orders,77families and156genuses.122fishes from thefamily Perciformes (accounting for49.57%of the total species),22fishes from the familyCypriniformes (9.40%of the total species). And there were59.8%warm water fishes,37.8%warmtemperature fishes and1.69%cold temperature fishes. the taxonomic distinctness Δ+and variationsin taxonomic distinctness Λ+in the Jiulong River estuary was73.793and144.444respectively.Only Sep.2010is significantly different from the total name list（P<0.05）. The rest months wasnot significantly different from the total name list.Second, the fish assemblage of the Jiulong River Estuary was studied in Sep.2010~Aug.2010and Sep.2011~Aug.2012. A total of202fish species were collected in Sep.2010~Aug.2010, belonging to2classes,19orders,72families and136genuses. The most of fish species at-tributed to Perciformes（107），20fishes from the family Cypriniformes. A total of160fishspecies were collected in Sep.2011~Aug.2012, belonging to1classes,14orders,64families and119genuses. The most of fish species attributed to Perciformes（81），16fishes from the familyAnguilliformes. Shannon-Weaver biodiversity index H was higher in Sep.2010~Aug.2010than inSep.2011~Aug.2012，and the average biodiversity index of fish were3.368and3.364separate-ly. The biomass and abundance differed significantly in Sep.2010~Aug.2010and Sep.2011~Aug.2012. The average biomass and average abundance were35177.09g/net and15517ind/netrespecttively. And the dominant species included Sardinella aurita、Ambassis gymnocephalus、Mudil affinis、Anchoviell achinensis、Clupanodon punctatus,which reached48.15％of the totalcatches. The average biomass and average abundance were40013.72g/net and18511ind/net re- specttively. And the dominant species included Ambassis gymno-cephalus、Mudil affinis、Sardinella zunasi, which reached37％of the total catches.The third, The fish assemblage was examined along a salinity gradient of the Jiulong RiverEstuary situated in Fujian. A total of162fish species, were collected in Daomei site; a total of147fish species in FuGong site;a total of105fish species in ZiNi site. By the statistical tests,fish species numbers significantly varied among different salinity gradients (P<0.05),whichreflected the fish species number of the inner regions of the estuary increased gradually seawardtrend. Similarity analysis showed that the fish community composition of the three differentsalinity water in Jiulong River Estuary was the most similar in the middle(Fugong)and theupper(Zini)water, that was habitat difference was minimum. The biggest differences of the fishcommunity composition was in the lower(Daomei) and the upper(Zini), and habitat differencewas maximum; the similarity coefficient between different season in the same water generallywas higher than that of the different salinity water,which suggested that under the same water indifferent seasons, the degree of similarity of fish species composition was lower than that of thedifferent salinity water.The fourth, a preliminary survey of the food relationship was carried out in the Jiulong Riv-er Estuary, Fujian from Sep.2010to Aug.2012.According to their dietary habits, they may be div-ided into six types: planktivorous,benthophagous,nektivorous, planktivorous-benthophagous, pl-anktivorous-nektivorous, and benthophagous-nektivorous. Based on the relationship among eachnutrient class in foodweb, they may primarily be divided into four nutrient classes:omnivores, lo-wer carnivores,middle carnivores, higher carnivores. Most of them are the lower carnivores.