Preliminary Study Of Fish Community Structure In Yellow River Estuary Waters

Yellow River is the second longest and the thickest silt concentration river inChina. it transports a lot of water, sediment and nutrient salts to estuary waters everyyear, and creates a suitable environmental conditions, nutrient-rich and many speciesYellow River estuary waters, which is a spawning, feeding and nursing ground andalso the important fishery production in Bohai sea. In recent decades, the fishcommunity structure has been great changed because of overfishing, reduced run off,water pollution and WSDR (water and sediment discharge regulationproject).In order to know the fish community structure in Yellow River Estuary waters,based on the fish data were collected in May, June, July early(D), July late(A), Augustand September of2012by using bottom trawl which is a30.6m width and a20mmnet mesh surveys on six different voyages. The trawl speed was about3nautical milesand the trawl time was30-60minutes, and the fish data were standardized beforeusing them. In the investigate area,37°40′~38°15′N,119°00′~119°40′E,15samplestations were setup.index of relative importance (IRI), diversity index such asMargalef richness index (D), Shannon-Wiener diversity index (H’) and Pielou’sevenness index (J’), hierachical cluster (CLUSTER), non-metric multi-dimensionalscaling (MDS), SIMPER, canonical correspondence analysis (CCA) were used in thispaper. Meanwhile, taxonomic diversity was used to contrastive analysis fishcommunity of Yellow River Estuary, Yangtze River Estuary, Pearl River Estuary andtheir adjacent waters based on the available survey data and historical survey data. So,our work could provide valuable information on assessing the fish resources andmaintaining the sustainable development of the Yellow River Estuary ecosystem, andalso could offerreference for reasonable carrying out the water and sediment dischargeregulation (WSDR).1. To investigate characteristics and monthly variations of fish communitystructure, fish data were collected from may to spetember by using bottom trawl in Yellow River Estuary waters. The results show that a total46fish species were caught,belonging to8orders,26families and42genus, which mainly composition werewarm temperature species (30species), marine species (27species) which includedmarine migrant species (18species) and marine straggler species (9species), estuarinespecies (18species) Perciformes (22species). The Perciformes were the mostabundant (22species). The dominant species of fish community showed a bigvariation, the dominant species which in May and June were Chaeturichthysstigmatias, Enedrias fangi, Cynoglossus joyeri, etc, and in July, August andSpetember were Konosirus punctatus, Sardinella zunasi, Engraulis japonicas andChaeturichthys stigmatias, ect, and the Chaeturichthys stigmatias was in commondominant. The catch per unit effort with a significant changes in different season, thebiomass and numbers were low in May and June and was the most of estuarinespecies stock, but which were high in July August and Spetember and was the most ofmarine species stock. The stock was the lowest in May, while the highest in August.The fish community diversity were low overall in July, but in July early(D) were thelowest in all survey months. CLUSTER and MDS analysis indicated that the fishcommunity were divided into2groups which were A (5-6) group and B (7-9) group,and the marine species Konosirus punctatus, Sardinella zunasi and Engraulisjaponicas, ect were the characteristic species that caused significant difference.2. To know the relation between fish community structure and environmentalfactors, fish data and environmenta data were investigated during the water andsediment discharge regulation from june to july2012in Yellow River Estuary waters.The result showed that a total number of39species were caught in three surveys,belonging to8orders,23families and37genera, the major order was Perciformes.The dominant community were demersal fishes and the percentage of biomass was95.7%in before WSDR and the dominant species was only Chaeturichthys stigmatias,but the dominant community were mainly pelagic fishes and the percentage ofbiomass were72%and67.1%in during and after WSDR and the dominant specieswere Chaeturichthys stigmatias, Konosirus punctatus, Sardinella zunasi andEngraulis japonicas. The average relative biomass was6.4±1.9kg/h and the everystation biomass was relative equality in before WSDR. The during WSDR biomasswas62.1±29.1kg/h and distributed in offshore area, especially in the northwestwaters of estuary. The after WSDR biomass was48.2±17.2kg/h and distributed inestuary and southeast area. The Margalef richness index (D) was1.24±0.10, 1.27±0.08and1.35±0.08in three surveys and increased in turn, but had no significantdifference (P>0.05). The Shannon’s diversity index (H’) was0.63±0.04,0.36±0.04and0.50±0.04and the Pielou’s evenness index (J’) was1.44±0.09,0.93±0.11and1.24±0.09, of which the highest in before WSDR and the lowest in during WSDR, H’and J’ had significant difference (P<0.01) in three surveys. CCA indicated thattemperature, salinity and depth had the most important effects to the distribution ofthe fish community, meanwhile suspended solids (turbidity) also decided spacialdistribution of fish community.3. to understand the differencesof fish taxonomic diversity during Yellow RiverEstuary, Yangtze River Estuary and Pearl River Estuary waters, the available andhistorical survey fish data were gathered. The results showed that there were1210species of fishes recorded and belonged to2classes,32orders,189families,548genera in all three estuaries. The Yellow River Estuary waters there were198species,belonging to2classes,21orders,65families,133genera. The Yangtze River Estuarywaters there were338species, belonging to2classes,27orders,102families,230genera. The Pearl River Estuary waters there were1009species, belonging to2classes,26orders,157families,454genera. The major order was Perciformes. Theaverage taxonomic distinctness Δ+were77.2,78.9and76.7, and the variation intaxonomic distinctness Λ+were310.0,272.7and240.0. The average taxonomicdistinctness Δ+and the variation in taxonomic distinctness Λ+in Yellow River Estuaryand Yangtze River Estuary were higher than Pearl River Estuary, which showed thatthe Pearl River Estuary taxonomic diversity was poorer, genetic relationship of fishcommunity was nearer, and the degree of concentration of species on taxonomiccategory was lower than the other two. Meanwhile, by compared with other sea area,the average taxonomic distinctness Δ+was the highest in the estuary waters. Thesimilarity index showed that the similarity of Yellow River Estuary and Pearl RiverEstuary was the lowest in all taxonomic levels and had a large different in speciescomposition.