Effects of different substrate types on community characteristics of benthic swimming organisms in the artificial reef area

In order to explore the impact of different substrate types after the deployment of artificial reefs on the community structure characteristics of benthic swimming species, six cruises of field surveys were conducted in the artificial reef area located in the Xiaozhushan Island. The survey area was divided into three transects with a radius of 200 m, 400 m, and 600 m based on the artificial reef modules deployed in the center of the sea area. Trap and visual census methods were combined to sample benthic swimming organisms in June, August 2017, June 2018 (twice), and June, July 2019. Relative importance index (IRI), principal coordinate analysis (PCoA) and one-way analysis of variance (ANOVA) were utilized to explore the variance of spatial-temporal constitution of the community, and General additive model (GAM) was utilized analyze the effects of environmental factors to catch per unit effort (CPUE) and biodiversity index of the community. The results showed that two sampling methods totally obtained 47 species in 5 categories, including 38 species from trap, 28 species from visual census and 19 species in common. IRI and PCoA indicated that Charybdis japonica, Asterina pectinifera, Hexagrammos otakii, Sebastes schlegelii, and other fusiform fish were mainly captured by trap; Echinodermata such as A. pectinifera, Palaemon graviera, Tridentiger trigonocephalus,Amblychaeturichthys hexanema, Triaenopogon barbatus and Chaeturichthys stigmatias were mainly captured by visual census. One-way ANOVA of both sampling methods indicated that the CPUE of 200 m and 400 m transects was significantly higher than 600 m transect, but there was no significant difference between years. GAM showed CPUE increased with the rising complexity of substrate types and duration of the deployment of artificial reefs, was positively correlated with substrates of artificial reef and rock, and was affected by salinity and temperature. In addition, GAM showed that biodiversity index of trap was significantly higher than visual census, and it was influenced by salinity and transparency. But there was no connection with substate types. This study revealed the effects of different substrate types to benthic swimming organisms, proved the complementary of the combination of trap and visual census, and provided a reference for the management of reef substrate.