Assessment of fishery resources in southern sea area of Yintan Marine Ranching, Guangxi Province

In order to understand the status of fish resources in the Beihai Yintan Marine ranching sea area of Guangxi Province, we conducted two acoustic surveys with a split-beam scientific echosounder (Simrad EK80) in March 2022 and January 2023. We evaluated the fish density, fish biomass density and spatial distribution in the surveyed sea area by using echo integration method combined with trawl sampling (Mesh size: 4.0 cm×2.5 cm). The results show that both in the artificial reef area and control area, the catches were mainly composed of small individuals (Average masses of individuals in 2022 and 2023 were 8.64 and 29.8 g, respectively). In March 2022, the average fish densities of acoustic evaluation species in the artificial reef area and control area were 66 003 and 41 903 inds·km⁻², respectively. The average fish biomass densities in the artificial reef area and control area were 726.66 and 469.9 kg·km⁻², respectively. In January 2023, the average fish densities of acoustic evaluation species in the artificial reef area and control area were 17 194 and 11 110 inds·km⁻², respectively. The average fish biomass densities in the artificial reef area and control area were 665.94 and 406.85 kg·km⁻², respectively. The artificial reef area showed a significant fish catching effect. The fishery resources were distributed mainly in water layers below 5 m, and those in reef areas had a wider vertical distribution range than the control area. The average target strength (TS) of the two survey voyages in the artificial fish reef area were greater than that in the control area, and more single targets were detected in the artificial fish reef area with a more concentrated distribution than in the control area. The results reveal the impact of artificial reefs on the redistribution of fish resources.