Acoustic estimation of fisheries resources off Ma’an Archipelago

In order to know the spatial and temporal distribution of fishery resources and their relations with the environment in island and reef area of Ma’an Archipelago, BioSonics DT-X echosounder was used to conduct three acoustic surveys with trawl sampling in December 2016, March and May 2017. The results showed there were 46, 32 and 43 species estimated respectively in December 2016, March and May 2017, and the average abundance density were 2.7×10⁴, 1.98×10⁴ and 1.45×10⁴ ind/km², and the average biomass density were 0.33, 0.34 and 0.30 t/km². The biomass were 132, 141 and 126 t in the three fishery resources. The fish abundance density decreased gradually over 3 times, the biomass density and biomass were the highest in March, followed by December and May. There was no significant linear relationship between depth and resource density, which were the highest at the bottom layer, followed by middle layer and the least value at surface layer. There was a significant positive correlation between the abundance density of the bottom layer and the silty content of the sediment (R²>0.75). There was no significant linear relationship with fishery abundance density and temperature and salinity of each month, and there was a certain linear relationship with dissolved oxygen (R²=0.72) in the near reef area, where the fishery abundance density was much higher than that in the far reefs. There was a significant linear relationship between fishery abundance density and temperature (R²=0.91), and the linear correlation with the dissolved oxygen was weak (R²=0.63), and there was no significant linear relationship with the salinity. The research confirmed that the acoustic method showed good effects in island and reef area of Ma’an Archipelago of fishery resources assessment, providing the scientific basis and realistic foundation for further study on the effect assessment of island and reef and artificial reef area.