Niches and interspecific association of major shrimp and crab species in Pishan waters of Zhejiang Province, China.

Based on the fishery resource investigation data in Pishan waters of Zhejiang coastal area in November of 2015 (autumn), February (winter), May (spring) and August (summer) of 2016, we analyzed the spatio-temporal niche characteristics and interspecific association of the domi-nant shrimp and crab species using the methods of niche test, variance ratio, chi-square test, Spearman test and redundancy analysis. A total of 34 shrimp and crab species belonging to 14 families and 20 genera were identified. Among them, 10 species were collected in all the four seasons. Dominant species were Parapenaeopsis hardwickii, Exopalaemon carinicauda and Portunus trituberculatus. The temporal, spatial and spatio-temporal niche breadths of the major shrimp and crab species ranged from 0.03-1.34, 2.07-3.63 and 0.08-4.64, respectively. The cluster analysis of niche breadths suggested that all the species could be divided into narrow, medium and wide niche breadth groups under the 90% similarity level. In addition, the spatio-temporal niche overlap values of the major species in Pishan Sea were mainly at low level (68.9% of the species's Qik<0.3), implying little interspecific competition for resource utilization. The analysis of variance ratio showed that the major shrimp and crab species were mainly positively correlated, with 11.1% of the species showing significantly positive association. The JI index, OI index and Spearman test all showed the relationship between major shrimp and crab species tended to be positive correlation as a whole. Redundancy analysis showed that surface temperature, bottom temperature, and surface salinity were the main environmental factors affecting the distribution of shrimp and crab species in Pishan waters.

Spatio-temporal niche of major fish species in Pishan waters off Zhejiang Province, China.

Based on seasonal bottom trawl surveys in November 2015 (autumn), February (winter), May (spring) and August (summer) in 2016, the index of relative importance (IRI), Shannon index and Pianka index were used to analyze the breadth and overlap of spatio-temporal niche of major fish species in the Pishan waters off Zhejiang Province. Redundancy analysis and interspecific competition coefficient were used to examine the competition relationship and niche differentiation of those major fish species. The results showed that a total of 61 fish species were recorded throughout the year, which belonged to 13 orders, 29 families and 48 genera. A total of 19 species with IRI>100 were identified as major fish species. The temporal niche overlap value between Chelidonichthys kumu and Atule kalla was largest, indicating high temporal synchronization. Both the spatial niche overlap value and the spatio-temporal niche overlap value between Trpauchen vagina and Cynoglossus interruptus were largest, indicating that their spatial homology was high and that the use of spatial and temporal two-dimensional resource of both species were consistent. The percentage of species pairs with spatio-temporal niche overlap at the significant level (Qik>0.6) was only 5.8% in Pishan waters, indicating that the spatial and temporal distribution of those species were quite different. The overlap of spatio-temporal niche significantly varied across different seasons. The results of the interspecific competition coefficient were basically consistent with the niche overlap. Results of the redundancy analysis revealed the relationships between major fish species and environmental factors (temperature, salinity, dissolved oxygen), and further explained the niche diffe-rentiation among species.

[Niche and interspecific association of major nekton in the sea area to the east of the Nanji Islands]. / 南麂列岛东侧海域主要游泳动物生态位及种间联结性.

According to the fishery resources investigation data in the east of the Nanji Islands during autumn in 2017 and spring in 2018, the inter-specific relationships and ecological relationships between major nekton were analyzed via the index of relative importance, niche breadth, cluster analysis, niche overlap, χ2-test, variance ratio test, association coefficient, percentage of co-occurrence, and point correlation coefficients. The results showed that there were 30 major nekton species in this area. The dominant species were Harpadon nehereus, Portunus trituberculatus, and Oratosquilla oratoria. The niche width of these dominant species was relatively wide. Based on the cluster analysis of niche breadth, the 30 major nekton species could be divided into three categories, wide niche breadth species, moderate niche breath species, and narrow niche breath species. The distribution range of niche overlap value was [0, 0.98], indicating that there were differences in the similarity of species to resource utilization and that the niche was differentiated and accompanied by inter-specific competition. The values of VR and W showed that there was a significant positive correlation among the major nekton species. The χ2-test results indicated significantly interspecific association for 76 species pair (χ2≥3.841), which was related to community stability and species coexistence. Results of association coefficient, percentage of co-occurrence and point correlation coefficients test suggested that the interspecific association was strong and tended to be positive.

[Community structure of zooplankton in adjacent area of Changjiang Estuary, China in 2016.] / 2016年夏季长江口邻近海域浮游动物群落结构.

Based on the data of zooplankton samples from 27 stations in the offshore area of Changjiang Estuary in August 2016, we analyzed the community structure and diversity of zooplankton and examined the relationship between zooplankton community structure and environmental factors. A total of 108 species of zooplankton belonging to 12 groups in six phyla, together with 15 types of pelagic larvae and fish eggs were identified. The main groups were copepods, thaliacea, chaetognaths, cladocladus and medusae, with the average abundance being 273.9, 115.0, 67.1, 63.6 and 61.1 ind·m-3. The most dominant group of zooplankton was copepods (48 species), accounting for 44.4% of the total zooplankton abundance. Medusae ranked second with a total of 12 species, accounting for 11.1% of the total zooplankton abundance. Furthermore, the absolute dominant group was copepods, with the highest contribution to the zooplankton community (20.3%). According to the clustering results of environmental factors, the area could be divided into Changjiang diluted water and offshore water mass. The results of analysis of similarities showed that the difference of zooplankton community between the two regions was significant (the average diffe-rence was 4%), and the contribution to the difference was 20.3%, 18.0%, 14.1%, 13.4%, and 11.8% for copepod, thaliacea, cladocera, chaetognaths, and medusae, respectively.

[Community structure of fish in Zhoushan Fishing Ground and its adjacent waters in spring and summer].

Based on the investigation data of the fishery resources and environment in Zhoushan Fishing Ground and its adjacent waters in August 2006 and April 2007, and by using multi-dimensional scaling (MDS) and canonical correspondence analysis (CCA), this paper studied the species composition and the characteristics of fish community in the area. In spring, a total of 62 fish species were captured, belonging to 56 genera, 36 families and 11 orders. The dominant species were Amblychaeturichthys hexanema and Larimichthys polyactis, and their abundance occupied 82. 9% of the total. In summer, 58 fish species were captured, belonging to 51 genera, 38 families and 11 orders. Amblychaeturichthys hexanema, Champsodon snyderi, Dysomma anguillaaris and Acropoma japonicum were the dominant species, with the abundance accounted for 60.8% of the total. In the two seasons, twenty stations were separated into three groups. Among the fishes captured, 26 and 30 fish species had an occurrence rate larger than 5.0% in spring and summer, respectively, and formed two and three assemblages correspondingly.

[Analysis on community structure of zooplankton in Zhoushan fishing ground and its adjacent area in summer].

Based on the data acquired within the Zhoushan fishing ground and its adjacent area (29 degrees 30' - 31 degrees 30' N, 121 degrees 30' - 124 degrees 30' E), species composition, abundance, and species diversity of zooplankton were sampled by plankton net (50 cm mouth-diameter, 145 cm net length, 0.505 mm mesh-aperture) during August 2006. The results identified 93 species (exclude Larvae) from the samples, among which Copepods were the most diverse with 50 species. According to the standard of IRI (the species with IRI above 0.02 were regarded as dominant species in this paper), there were 12 dominant species: Euchaeta concinna, Dolioletta gegenbauri, Sagitta enflata, Sagitta bedoti, Calanus sinicus, Undinula vulgaris, Canthocalanus paupe, Macruran larvae, Diphyes chamissoni, Centropages dorsispinatus, Evadne tergestina, Acartia pacifica. The stations of high abundance were mainly in the southern part and oceanic sea, and low in the northern and near shore waters. Zooplankton in the Zhoushan fishing ground and its adjacent area exhibited high in evenness (0.70), high species number and high diversity indices (4.98). By hierarchical cluster analysis and non-metric multidimensional scaling (MDS) assisted analyzing, zooplankton in Zhoushan fishing ground and its adjacent area could be formed into three assemblages joining at a distance of 17.13%. The biota-environment matching (BIOENV) analysis showed that the abundance of zooplankton was correlated closely not only to salinity, nitrate, silicate, but also to the Cd and Pb.

[Structural characteristics of crab communities in offshore waters of mid-southern East China Sea].

The crab resources in the offshore waters of mid-southern East China Sea (26 degrees 00'-28 degrees 30' N, 121 degrees 00'-126 degrees 00' E) were investigated in May (spring), August (summer), November (autumn) 2006 and February (winter) 2007, with the characteristics of their community structure, including species composition, index of relative importance (IRI), diversity, and biomass analyzed. A total of 49 species were identified, belonging to 30 genera and 12 families. In both spring and autumn, the crab species number was higher in northern than in southern part of the Sea; in summer, it had a relatively uniform distribution; while in winter, less difference was observed between the southern and northern parts of the Sea, and the crabs were mainly concentrated in the exterior areas. A total of 13 dominant species (IRI > 1000) with Charybdis bimaculata, Calappa lophos, Charybdis miles, Ovalipes punctatus, Carcinoplax longimana, Charybdis riversandersoni, and Portunus argentatus as the representatives appeared all the year round. The diversity index of the crabs was lower in summer, but had no significant difference among the other three seasons. The catching mass of the crabs in the investigated sea area was averagely 5197.62 g x h(-1), being 8830.79 g x h(-1) in summer > 4877.50 g x h(-1) in spring > 4268.30 g x h(-1) in autumn > 2813.87 g x h(-1) in winter. The crabs in the offshore waters of mid-southern East China Sea could be categorized as 3 ecological communities, i. e., eurythermal and eurysaline, hyperthermal and eurysaline, and hyperthermal and hysaline.