Spatial distribution characteristics of Oratosquilla oratoria and its relationship with environmental factors in Rui'an Sea area

In order to study the spatial distribution characteristics of Oratosquilla oratoria in Rui'an Sea area in different seasons and their relationship with environmental factors, this study was carried out to investigate the relative importance index, spatial distribution and center of gravity variations as well as seasonal variations of body mass of O. oratoria based on the bottom trawl and environmental surveys of four cruises in Rui'an Sea area obtained in April (spring), August (summer), November (autumn) 2021, and January (winter) 2022, and to the GAM model was applied to explore the key environmental factors affecting the density distribution of O. oratoria resources. The results showed that: O. oratoria are the dominant species in four seasons in the Rui'an Sea area, and are important benthic species in the Rui'an Sea area. The average resource density of O. oratoria in Rui'an Sea area was 115.00 kg/km² throughout the year, and the average resource density of O. oratoria showed that winter > autumn > summer > spring, and there was no significant difference in the resource density of O. oratoria in all seasons. O. oratoria were distributed in the waters east of Beiji Island at a depth of 20 m in spring and winter, and in the waters adjacent to Beilongshan, Beiji Island and Nanji Island in summer and autumn; the center of gravity of the density of resources showed a tendency to move toward the nearshore from spring to autumn, and to move toward the offshore from autumn to winter. The average body mass of O. oratoria was spring > summer > autumn = winter, and there was no significant difference in the body mass of O. oratoria between seasons. The GAM model showed that longitude, water depth, surface water temperature and bottom water temperature showed highly significant effects on the density of O. oratoria resources. O. oratoria showed a highly significant linear relationship with water depth, and a highly significant non-linear relationship with longitude, surface water temperature and bottom water temperature. The results show that the adjacent waters of Beiji Island may be an important place for spawning and larval fattening of O. oratoria in Rui'an Sea area. Longitude, depth and water temperature are important factors affecting the resource density distribution of O. oratoria in Rui'an Sea area. This study reveals the dynamic change pattern of O. oratoria resources in Rui'an Sea area, which provides a reference basis for rational utilization and protection of O. oratoria resources.