Relationship between center of gravity and environmental factors of main catches of purse seine fisheries in North Pacific high seas based on GAM

Light seine fishery in North Pacific high seas is a new offshore fishery project in China in recent years. Scomber japonicus, Sardinops sagax, Ommastrephes bartramii and Cololabis saira are the main economic species in that area. It is important to clarify the relationship between the center of gravity and environmental factors for the study on the formation mechanism of fishery and the guidance of fishery production. Based on the 2016−2017 North Pacific Light Seine Fishery catch data and environmental factors such as sea surface temperature (SST) and chlorophyll a (Chl-a), we analyzed the seasonal variation of catch and its relationship with environment were analyzed by generalized additive model (GAM). On the whole, the center of gravity of North Pacific fisheries shifted northeast at the beginning of the fishing flood, and turned southwest during August to late September. The results show that S. japonicas fishing grounds were mainly at 148°E−154°E, 40°N−42°N; S. melanostictus fishing grounds were mainly at 149°E−153°E, 40°N−42°N; O. bartramii fishing grounds were mainly at 150°E−154°E, 40°N−42°N; C. saira fishing grounds were mainly at 150°E−153 °E, 41°N−42°N. Moreover, the optimal SST of S. japonicus CPUE was 13−20.18 ℃, and the optimal Chl-a was 0.1−0.8 mg·m⁻³. The optimal SST of S. sagax CPUE was 12−19.1 ℃, and the optimal Chl-a was 0.3−0.88 mg·m⁻³. The optimal SST of O. bartramii CPUE was 14−22 ℃, and the optimal Chl-a was 0.2−1.1 mg·m⁻³. The optimal SST of C. saira CPUE was 14−21 ℃, and the optimal Chl-a was 0.24−0.98 mg·m⁻³.