| This study was based on the fish community investigation in Qinglan mangrove areas,Hainan province.Samplings were conducted at two sections(Touyuan and Paigang)in June,September,December 2015 and March 2016.The main characterists of fish community,including species composition,ecological type,dominant species and diversity index and their seasonal and spatial changes were described.Moreover,Cluster analysis,non-metric Multi-Dimensional Scaling analysis(nMDS),analysis of similarity(ANSOIM)and similarity of percentage(SIMPER)were used to analyse the spatio-temporal patterns of fish community.In addition,the study results were compared with results of similar studies in other mangrove areas of China,and the commonalities and differences of fish community among different mangrove areas in China were discussed.Furthermore,the ecological support role for fish community played by Qinglan mangrove areas,such as the nursery,shelter and feeding grounds and the relationship between mangroves and nearshore fisheries of Qinglan bay were discussed.The main results and conclusions are as follows:1.Seventy-eight species were collected in Qinglan mangrove areas,belonging to 39 families,12 orders and 2 classes;the most abundant order was Perciformes,which included 45 species of 19 families accounting for 57.7%of the total species;Gobiidae was the highest diversity family which in total of 10 species.Individual number of most species was 1?100,which in total of 60 species accounting for 76.9%of the totals;Only 5 species whose individual number was over 500.As for the inhabiting depth,there were 43 demersal species,25 pelagic species,10 near-demersal species which accounting for 55.1%,32.1%and 11.5%respectively.Based on the thermophily,there were 69 warm-water species and 9 temperate-water species which accounting for 88.5%and 11.5%respectively.For feeding habits,there were 53 carnivorous fish,24 omnivorous fish which accounting for 67.9%and 30.8%respectively;only one phytophagous fish was collected,which is Siganus guttatus.2.According to the Jaccard similarity results,over the four seasons,similarity of species composition between spring and winter was highest,which the Jaccard value is 0.59;the secondary high similarity was between autumn and winter,which the value is 0.53;similarity between summer and autumn and between spring and summer were both lower,which the value were 0.42 both.Results of SIMPER showed that species with greater contributions to the similarity between sections and dissimilarity among seasons were mainly the nearshore pelagic fish and demersal fish,the sedentary species in mangroves had less contribution.3.The dominant species varied with seasons.Moolgarda cunnesius,Mugil cephalus,Gerres limbatus,Glossogobius giuris and Sardinella brachysoma were dominant species in summer;Escualosa thoracata,Gerres limbatus,Liza carinata,Gerres filamentosus,Glossogobius giuris,Moolgarda cunnesius and Mugil cephalus were dominant species in autumn;Escualosa thoracata,Sardinella brachysoma,Glossogobius giuris,Liza carinata,Gerres abbreviates,Gerres filamentosus and Sillago sihama were dominant species in winter;Glossogobius giuris,Escualosa thoracata,Stolephorus chinensis,Clupanodon thrissa,Oligolepis acutipennis,Sillago sihama,Dendrophysa russelii,Mugil cephalus and Liza carinata were dominant species in spring.Overall,the main dominat species of all seasons were nearshore pelagic fish,such as Mugilidae,Clupeidae and Engraulidae.Only Glossogobius giuris was dominant all the year round.There were significant differences on dominant species between two sections:Gerres limbatus,Glossogobius giuris,Escualosa thoracata,Sillago sihama,Gerres filamentosus,Ambassis kopsii,Liza carinata,Oligolepis acutipennis,Solea ovate and Ambassis gymnocephalus were the dominant species in section Touyuan(a mudflat habitat),while Mugil cephalus,Moolgarda cunnesius,Escualosa thoracata,Liza carinata,Sardin.ella brachysoma and Clupanodon thrissa were the dominant species in section Paigang(open water areas outside mangroves).There were more dominant species in section Touyuan and the main dominant species in Touyuan were nearshore or sedentary demersal and near-demersal fish;while in Paigang,the dominant species were all nearshore pelagic fish.The common dominant species of two sections were only Escualosa thoracata and Liza carinata.4.The seasonal changes of number of species,Shannon-Wiener diversity index(H'),Pielou eveness index(J)and Margalef species richness index(D)were all spring>autumn>winter>summer.As for sections,number of species,H',J and D in Touyuan were all higher than that in Paigang,which indicated that the diversity of fish community and the species abundance in Touyuan were higher than in Paigang.5.According to the results of CLUSTER and nMDS,the fish community in Qinglan mangrove areas was divided into two main groups:group ?:Paigang summer,Paigang autumn,Paigang winter and Paigang spring;group ?:Touyuan summer,Touyuan artumn,Touyuan winter and Touyuan spring.The subdivided results of this two main groups showed that the seasonal changes in Paigang were more evident than in Touyuan.The results of ANOSIM showed that there was significant difference on fish community between two groups(R=0.87,P<0.05),which meant that there was significant difference on fish community among all sections and all seasons in Qinglan mangrove areas.Based on the results of SIMPER,the average similarity of fish community within group ? was 36.97%,while this value within group ? was 51.05%.The indicator species(species which has more that 5%contribution on similarity within a group)of group ? were Mugil cephalus,Moolgarda cunnesius,Elops saurus,Escualosa thoracata,Liza carinata,Sardinella brachysoma,Clupanodon thrissa and Leiognathus equulus,which indicated that group ?(section Paigang)was a fish community mainly consisted pelagic fish,such as Mugilidae and Clupeidae;while the indicator species of group ? were Glossogobius giuris,Gerres filamentosus and Gerres limbatus,which indicated that group ?(section Touyuan)was a fish community mainly consisted sedentary fish(such as Glossogobius giuris)and nearshore demersal fish(such as Gerreidae).6.Compared with similar studies in other mangrove areas of China,the commonalities and differences on fish community of different mangrove areas were summarized as follows:a.Mangrove areas where situated at the lower latitude,with wider areas of mangrove and less selectivity of sampling gears,number of species is larger,too;b.There are more demersal fish in mangrove creek and mudflat,while in open water areas outside mangroves or in mangroves with high tidal range,there are usually more pelagic fish;only warm-water and temperate-water species are found in mangrove areas,and warm-water species is the majority;carnivorous fish and omnivorous fish are much more than phytophagous fish in mangroves;c.Dominant species vary with seasons in all mangrove areas,the composition of dominant species varies with regions;however,based on taxa of family,the composition of dominant taxa are similar in different mangrove areas:all mainly consist nearshore or estuary pelagic fish(represented by Mugilidae,Clupeidae and Engraulidae)and sedentary fish in mangroves(represented by Gobiidae and Ambassidae);d.Overall,the diversity index in habitats of mangroves are mudflat>creek>open water areas outside mangroves,while the eveness index(J)is usually higher in mangrove creeks.7.Qinglan mangrove area plays an essential role of ecological support for fish community,which reflected in:a.Besides the sedentary fish of mangroves,the standard length of other dominant species in mangrove areas were much less than the adult individuals,which meant that most non-sedentary fish were juveniles,and mangrove area can be a nursery ground for these fishes.b.With wide mangrove areas,abundant mangrove plants and high structure complexity,Qinglan mangrove area becomes an ideal shelter for many fishes.Moreover,no large ichthyophagous predators were found in Qinglan mangrove area,the pressure from predators was light in mangrove area,and fish can be well sheltered in Qinglan mangrove area.c.Nutriments in mangrove area were abundant,and there can be a "detritus food chain"in Qinglan mangrove area,making the mangrove area become an important feeding ground for fishes.8.Qinglan mangrove area is not an isolated system,connectivity exists between mangrove area and nearshore sea areas of Qinglan bay.By comparing the standard length of some common fishes among seasons and sections,it can be inferred that as the growth of individuals,these fishes are likely to shift their habitats from mangrove mudflat to open water outside mangroves and finally to the habitat of adults,Qinglan bay,and achieve a supplement to the fish population and the fisheries of Qinglan bay.Therefore,mangrove areas play an important role to the supplement and enrichment of inshore fishery resource,protecting mangroves is meaningful for the stabilization and development of inshore fishery resource. |
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