The Fish Community Structure And Its Relationship With Environmental Factors In The Ma'an Archipelago And Its Eastern Waters

To study the fish community structure in islands area and the spatial distribution of the fish community pattern and the main causes of the differences in different habitat conditions,a fishery-independent survey was conducted in August and December of 2016,February and May of 2017.The fish community composition,time and space of the area were analyzed by cluster analysis,non-metric multi-dimensional scale(NMDS)and other methods.Dynamic research was carried out.The spatial distribution map of fish resources density(resource quantity and abundance)was plotted by MATLAB software,and the productivity level and nutrient conversion efficiency of fish community were studied by fish size spectrum method.The relationship between fish community pattern and environmental factors was analyzed by means of Pearson phase relationship analysis and bioenvironmental correlation analysis.The results showed that: a total of 96 species were collected,which belonged to 77 genera,47 families and 12 orders.he Perciformes has maximum ratio,which accounted for more than 50% of their biomass and abundance.Harpadon nehereus was the dominant species throughout the year.In addition,the dominant species in spring were Psenopsis anomala,Collichthys niveatus,and Cynoglossus robustus;the dominant species in summer were Larimichthys polyactis,Trichiurus lepturus,and Chaeturichthys hexanema;the dominant species in autumn and winter were Collichthys lucidus and Coilia Mystus.Cluster analysis and nMDS analysis of fish abundance and site showed that there were three groups of fish communities in the saddle islands and their eastern waters: Islands,reefs and offshore groups.In the three quarter of spring,summer and autumn,high catch stations were mainly distributed near the island and reefs in the spring,summer and autumn,and the high catch stations in winter were distributed in open waters.The average biomass showed that the average biomass in the three seasons of spring,summer and autumn was island reef group > near island group > offshore group.In winter,the average biomass was offshore group > near island group > island group.From the abundance CPUE,the overall distribution trend is the same as the relative resource density.In the three seasons of spring,summer and autumn,the high abundance CPUE area is mainly distributed near the islands and reefs.The high abundance CPUE area in winter is distributed in the far distant area of Islands reef.The highest points of the four seasonal abundance of CPUE were all at the island reef group site.According to the total amount and abundance of fish,the average weight of fish in different seasons was calculated.The average weight in summer,autumn and winter is reef group.The size spectrum of all fish communities in different seasons showed that the size spectrum intercept in spring was the largest,the productivity level was the highest,and the nutrient cycle efficiency decreased in summer,and the relative size spectrum decreased in autumn and winter.The results indicated that the nutrient cycle efficiency increased and the primary productivity decreased,and the size spectrum analysis of different groups in each season showed that the island and reef groups showed the largest intercept and the absolute slope of straight line in all four seasons.The results showed that the reef group had higher primary productivity and lower nutrient conversion efficiency,and the absolute slope and intercept of the near reef group were higher than that of the offshore group in spring and autumn.The results show that the near island group has higher primary productivity and lower nutrient conversion efficiency than the offshore group,but the winter is the opposite.The BIOEVN correlation analysis of fish composition and environmental factors(bottom water temperature,bottom salinity and sea depth)showed that the bottom water temperature had the greatest influence on the fish community.Pearson correlation analysis of the diversity index of fish community and environmental factors showed that the correlation of temperature was the strongest.In autumn,significantly positive correlation with the richness index and diversity index and temperature(p<0.01),evenness index and temperature were positively correlated(p<0.05);winter diversity index showed a significant negative correlation with temperature(p<0.05),was significantly negatively correlated with the temperature evenness index(p<0.01);in addition,a significant is winter richness and depth(p<0.05),showed a significant negative correlation with bottom salinity(p<0.05).The results showed that the pattern of fishery resources community in Ma'an Archipelago and its eastern waters was obviously affected by the seasonal migration of dominant species,and the habitat in the island and reef waters was more focused on the spawning site function,while the open sea area was more prominent as the habitat for adult fish.Under the synergistic action of primary productivity and habitat difference,and under the influence of environmental factors such as water temperature,water depth and salinity,the fish community showed significant temporal and spatial differences.