[Niche and interspecific associations of major nekton in northern coastal waters in Yuhuan, Taizhou, China].

Base on the data from fishery resources survey carried out in northern coastal waters in Yuhuan in November 2016 (autumn) and April 2017 (spring), we examined the niche and interspecific associations of major nekton by the methods of index of relative importance (IRI), niche breadth, niche overlap, the variance ratio (VR), X-test, association coefficient (AC), Jaccard index (JI), point correlation coefficient (Φ) and Spearman rank correlation index. The ecological niche breadth of Portunus trituberculatus was the largest, with the absolute competitive advantage. The niche breadths of the important economic species Coilia nasus and Octopus variabilis were the smallest, which was at a weak competitive position. The niche overlap of the major nekton species in this area was uneven, possibly caused by the diversity of local environments. Overall interspecific associations indicated that insignificant negative correlation existed among major nekton species. All results of the X-test, association coefficient (AC) and Jaccard index (JI) were consistent with that of overall interspecific associations, which indicated the independent trend among species. The correlation coefficients (Φ) and the Spearman rank correlation index revealed that the positive coupling pairs were more than the negative ones. It was due to the positive association among the other 14 species, caused by the spatial exclusion from large captured individuals of Muraenesox cinereus. According to the Spearman rank correlation and cluster analysis, 15 species could be divided into five ecological groups. The species within one ecological group had similar ecologically adaptable requirements of habitat, while the species from different ecological groups had different living habits and different ecological requirements.