Spatial distribution characteristics and seasonal variation of Oratosquilla oratoria in the southern coastal waters of Shandong Province

The present study analyzed the spatial distribution of Oratosquilla oratoria in the southern coastal waters of Shandong Peninsula based on bottom-trawl surveys in October 2016, January 2017, May 2017 and August 2017. We used center of gravity and Moran’s I index to estimate the distribution center of this species, compared the seasonal differences of spatial autocorrelation, and explored the potential influential factors of the spatial patterns. This study found substantial seasonal variations in the relative biomass of O. oratoria, which showed the highest relative biomass of 3.02 kg/h in summer, followed by 0.75 kg/h in spring, 0.65 kg/h in autumn and 0.22 kg/h in winter. The center of gravity showed remarkable seasonal changes, with the corresponding water depth ranging from 20 m to 30 m in spring and summer and from 30 m to 50 m in autumn and winter. The distributional pattern of O. oratoria was relatively consistent, exhibiting significantly positive spatial autocorrelation in four seasons. Moran’ I index was the highest in autumn (0.34), followed by spring (0.30) and summer (0.28), and was the lowest in winter (0.16). According to Moran’ I scatterplots, we identified survey sites with strong influence on biomass concentration. The seasonal changes in spatial distribution of O. oratoria might attribute to its spawning activities, and the biomass concentration implied that muddy silt and sand-silt-clay were the preference of sediment types of O. oratoria. We discussed the implications of our results for the management of O. oratoria and put forward the priorities for future fisheries research on spatial analyses.