Varitions In Fish Community Structure And Species Diversity In The Central Jiaozhou Bay

Based on the the data from bottom trawl surveys in the central Jiaozhou Bay from September 2008 to August 2009, the species composition, area types, quantity variations, dominant species and biodiversity were analyzed in this paper. Cluster and MDS were used to examine the composition of fish assemblage and seasonal change of fish community structure. Multivariate analyses were used to analyse the influence of environmental factors on fish species composition and biodiversity. The decadal variations in fish community structure were investigated according to historical research in 1980s, and the reasons for changes in fish community structure were discussed in Jiaozhou Bay.The main results of this study are listed as follows:1. There was 55 species collected from the surveys belongs to 1 Classe,8 Orders,30 Families and 47 Genera. There were 19 warm water fish species accounting for 34.55% of the total numer of fish species occurred,27 warm temperature fish species occupying 49.09%, and 9 cold temperature fish species amounting to 16.36%. There were 9 pelagic fish species accounting for 16.36%, and 46 bottom fish species amounting to 83.64% of the total number of fish species. The number of species was closely to seasonal change, which was presented in the four seasons as follows:Autumn(37 species)>Summer(34 species)>Spring(31 species)>Winter(29 species).2. The results of Cluster analysis showed that the fish community in the central Jiaozhou Bay could be divided into seven species groups, which correlated with the local species and migratory species. Each group was composed of fish species with different ecological types.3. The relative biomass and abundance varied dramatically in each month. The mean relative resources varied from 865.29 to 10511.80 g/(haul.hour) and from 111.45 to 1513.40 ind./(haul.hour) in the period of the surveys, which was the lowest in February and the highest in August. The mean resources density was 183 kg/km2, which varied from 38.93 kg/km2 in February to 472.99 kg/km2 in August.4. There was a distinct seasonal change in the composition of dominant species. The warm temperate and cold temperate resident species were dominant in winter and spring, and the warm water and warm temperate migratory species dominted in summer and autumn. Seasonal variations of the relative biomass and abundance of dominant species were correlated with those of the mean relative resources for the entire fish community.5. Margalef species richness index R varied from 2.08 in January to 3.25 in February, and the range of Shannon-Wiener diversity index H' was between 1.32 in August and 2.44 in November, with the Pielou evenness index J' being from 0.42 in August to 0.77 in March. There was no significant difference between seasons in each diversity index (P>0.05).6. According to the Cluster and MDS analysis, four month-groups of fish samples were classified, which were Groupâ… (Gâ… ,9,10,11),Groupâ…¡(Gâ…¡,12,1,2,3), Groupâ…¢(Gâ…¢, 4,5,6) and Groupâ…£(Gâ…£,7,8). ANOSIM analysis indicated that there were distinct differences in fish community structure between these four month-groups (P<0.01). The results of SIMPER analysis showed that the average similarity within-group was 42.57%, 40.18%,31.17% and 20.12% respectively, while group Gâ…¡and Gâ…£had the highest average dissimilarity value with 91.98%. The typifying and discriminating species for different month-groups were almost resident or warm ecological types.7. RELATE analysis showed that the species composition and monthly change of relative fish resources had a significant correlation with environmental factors. BVSTEP and BIOENV analysis showed that fish community structure was affected mainly by bottom temperature with bottom salinity combined (r=0.754). Correlation (Pearson) analysis revealed that there was no significant correlation between the biodiversity and environmental factors (P>0.05).Based on this study and historical researches, with the environmental factors taking into account, the decadal variations of fish community and species diversity were studied. The results showed that the biomass and number of species were low and the dominant species had changed from large-sized economically important fish to some small-sized bottom fish. The fish resources in the central Jiaozhou Bay had dramatically depleted.This paper provided the latest research material on fish community in the central Jiaozhou Bay, which would also offer the scientific basis for the fishery biodiversity conservation and sustainable development of Jiaozhou Bay ecosystem.