Optimization of fishery resources assessment methods and ecological effects evaluation of artificial reefs

Abstract

ABSTRACT The dynamics of fishery resources were analysed and compared before and after artificial reefs were deployed in the Dongshan Sea of Huizhou, Guangdong Province, China based on acoustic detection and trawl sampling methods. Species assessed by acoustic detection were mainly distributed in the middle water layers, and those collected by trawl sampling were mainly benthic organisms. Therefore, it was necessary to integrate the two methods aimed at organisms living in different water layers to improve the reliability of the assessment results. The comprehensive assessment results showed that the densities of fishery resources on artificial reefs and in the surrounding waters after the reefs were deployed were 58,302 inds/km2 and 69658 inds/km2, which were overall higher than that (60159 inds/km2) before artificial reef deployment. Some species, such as Parargyrops edita, usually hide inside the artificial reefs and cannot be detected or caught after the artificial reef deployment, which leads to a lower density being recorded than before artificial reef deployment. Furthermore, according to the results of single echo detection and nautical area backscattering coefficient analysis, the proportion of large- and medium-sized marine organisms increased after artificial reefs were deployed, and these organisms were mainly distributed in middle and deeper water layers. These observations indicated that the construction of artificial reefs could provide sufficient conditions for the growth of marine organisms and induce the large- and medium-sized individuals to deeper water layers.