In order to know the background information of fishery resources in Zhelin Bay-Nan'ao Island marine ranching,four acoustic surveys were conducted with Simrad EK60 echosounder in different months from April 2011 to February 2012.The results showed that the average abundance density and biomass density of 21 species estimated were 2.68×10⁴ ind/km² and 0.73 t/km² respectively in April 2011.The average abundance density and biomass density of 38 species estimated were 6.49×10⁴ ind/km² and 0.71t/km² respectively in August 2011.The average abundance density and biomass density of 33 species estimated were 4.14×10⁴ ind/km²and 0.93 t/km² respectively in November 2011.The average abundance density and biomass density of 15 species estimated were 1.45×10⁴ ind/km² and 0.36 t/km² respectively in February 2012.The fish density and biomass were the highest in November and the lowest in February.The nautical area scattering coefficient (NASC) was distributed mainly in 4～8 m depth layer in April and evenly in 4-14 m depth layer in August.In November the main depth layer was similar to that in April,but the percentage in the depth layer of higher than 10 m was higher than that in April.In February NASC was distributed mainly in 4-10 m depth layer (especially 6-8 m).No significant linear relationship was observed between fisheries resources density and water depth.Fisheries resources density did not show a significant linear relationship with sea surface temperature (SST) of station monthly.There was significant linear relationship between monthly average abundance density and SST (R²=0.997 4).A linear relationship between monthly average biomass density and SST was found (R²=0.287 2).Our research confirmed that the acoustic method showed good effects in the process of marine ranching fishery resources assessment,promoting the development of acoustic technology in the research field of marine ranching and providing the realistic foundation and scientific basis for our country to further study the effect and assessment of marine ranching enhancement in the future.