Temporal And Spatial Distribution Patterns Of Fish Assemblages From Mangrove Creek In The Nanliujiang River Estuary And Its Relationship With Environmental Factors

Combined effects of climate change,marine pollution,alien species invasion,coastal engineering construction and other factors have led to the reduction of mangrove area and loss of function,and biodiversity is facing a major threat.Therefore,the fish species composition and spatial and temporal distribution pattern from the mangrove creeks in the Nanliu River Estuary by non-metric multidimensional scaling were studied in this study,which aimed to explore the relationship between fish and environmental factors by redundancy analysis and generalized additive model.The results could provide a theoretical basis for the scientific protection,restoration and rational use of coastal wetlands and sustainable development of offshore fisheries.The main results of this study are as follows:(1)A total of 45 species(17680 fish individuals weighting 24724.73 g)were caught in this study,belonging to 12 orders,23 families,37 genera.The most abundant fish species was Perciformes,with 21 species belonging to 11 families,22 genera.In the order Perciformes,the number of species of Gobiidae was the largest,with 16 species.There were six dominant species in this area,such as Mugil cephalus,Ambassis urotaenia,Coptodon zillii,Gambusia affinis,Bostrychus sinensis and Synechogobius ommaturus.In addition,four alien species were found in this region,including G.affinis,Poecilia latipinna,C.zillii and Oreochromis niloticus.(2)Seasonal variation in fish assemblage structures were obvious(P = 0.001).The results of the three-ways ANOVA showed that species richness,total abundance,total biomass were significant differences between seasons(P < 0.05),which also were found in the total abundance and total biomass of six dominant species.(3)Fish assemblage structures were significantly different between spring tide and neap tide(P = 0.001).The results of the three-ways ANOVA showed that total abundance were significant differences between spring tide and neap tide(P = 0.004),while species richness and total abundance were insignificantly different(P = 0.666).Except for B.sinensis,the total abundance of remaining five dominant species(A.urotaenia,M.cephalus,C.zillii,G.affinis,S.ommaturus)were significantly different between spring tide and neap tide(P < 0.05).The total biomass of A.urotaenia,M.cephalus,G.affinis and C.zillii were significantly different between spring tide and neap tide(P < 0.05),while B.sinensis and S.ommaturus were insignificantly different(P > 0.05).(4)Spatial variation(among sites)in fish assemblage structures were unconspicuous(P > 0.05).Three-ways ANOVA showed that species richness and total biomass insignificantly different between sampling sites(P > 0.05),while total abundance showed significant differences in different sites(P < 0.05).The total abundance of M.cephalus,G.affinis and C.zillii were significantly different between sampling sites(P < 0.05),while A.urotaenia,B.sinensis and S.ommaturus were insignificantly different(P > 0.05).In terms of total biomass,G.affinis and C.zillii were significantly different between sites(P < 0.05),while A.urotaenia,M.cephalus,B.sinensis and S.ommaturus showed insignificant difference in sampling sites(P > 0.05).(5)Fish responds to environmental factors.The distribution of fish assemblage structures were affected by water temperature,Total nitrogen,salinity,tidal range,turbidity,creek width,and p H.Fish species diversity mainly drivered by water temperature and creek width,and the abundance of dominant species were affected by water temperature,p H,tidal range,Total organic carbon,creek width,turbidity and chlorophyll a.