Spatial heterogeneity of relationship between distribution of Uroteuthis chinensis and marine environment in offshore waters of northern South China Sea

Cephalopods are one of the most potienial fishery species but are vulnerable to environment changes, and their complex interactions lead to the spatial heterogeneity in resource-environment relationship. Uroteuthis chinensis is an important economic species in the offshore waters of northern South China Sea, occuping a dominant position in the fishery community structure. Therefore, understanding the spatial characteristics of the resource-environment relationship is beneficial to its development, utilization and protection. Based on the fishery resources survey data in the offshore waters of northern South China Sea in summer of 2014, we established a geographically weighted regression (GWR) model to explore the spatial characteristics of the relationship between the resource distribution of U. chinensis and the marine environment in this area, and to reveal the main influencing factors. The results of model evaluation indexes show that the minimum Akaike information criterion (AIC) and adjusted R-Square (R_\rmadj^2 ) for GWR model were 224.81 and 0.46, respectively, both of which were better than those of the traditional global linear regression model. Thus, the GWR model could more truly reflect the spatial heterogeneity on resource-environment relationship for U. chinensis. The impact of chlorophyll a on resources was a coexistence of positive and negative effects in the whole sea, but the other environment variables had consistent positive effects on resources. The stock distribution in the coastal waters of Guangdong was mainly affected by sea surface salinity, sea surface temperature and chlorophyll a, and the latter two were the primary influencing factors in western Guangdong and Pearl River Estuary-Eastern Guangdong, respectively, but the Beibu Gulf was only significantly affected by water depth. Under the impact of dominant environmental factors, U. chinensis stock denstiy showed obvious regional differentiation characteristics, especially those in the Pearl River Estuary-Eastern Guangdong significantly different from the other areas. In conclusion, GWR model provides an effective means to explore and understand the local characteristics of cephalopod resource-environment relationship.