## 3 Results
### Feature Importance Analysis  
The distribution of albacore fishing grounds is closely related to the geographical location of the sea area and the marine environment (SST, SSH, SSS and Chl-a). To quantitatively assess the effects of marine environmental factors on the forecast accuracy of different grades of South Pacific albacore fishing grounds, this paper explored the effects of different monthly marine environmental factors (Lat, Lon, SST, Chl-a, SSH and SSS) on the forecast accuracy of South Pacific albacore fishing grounds based on RF algorithm feature importance analysis. The RF algorithm obtains the importance ranking of each forecast factor by constructing a large number of decision trees to determine the contribution of different environmental factors to the fishing ground forecast [26,49]. The importance ranking of different marine environmental factors is shown in Figure 8.  
From February to December, Lat made the largest contribution to the forecast of different grades of South Pacific albacore fishing grounds, and it can be seen from Figure 8 that its contribution value was 0.224-0.377. This is because latitude is a basic factor affecting climate and is an indispensable environmental factor for the forecast of albacore fishing grounds, while the formation of environmental factors in different months is closely related to the geographical location. Chl-a had the largest effect on the forecast of albacore fishing grounds in the South Pacific Ocean in January (0.295), followed by 0.201-0.339 and 0.202-0.278 in February-May and August-December, respectively, while Chl-a had less effect on the forecast of albacore fishing grounds in other months. The importance ranking of each marine environmental factor in February was Lat > Chl-a > SSH > SST = SSS > Lon, and the importance ranking of different marine environmental factors for albacore fishing ground forecasts was the same in March, April and May (Lat > Chl-a > SST > SSH > SSS > Lon), while the contribution of each marine environmental factor to the albacore fishing ground forecasts was similar in May (Figure 8). In June-July, the influence of SST on the forecast of albacore fishing grounds exceeded that of Chl-a, with the contribution of Lat to the forecast of albacore fishing grounds reaching up to 0.377 in July, while the contribution of Lon was only 0.04. The contribution of SST was second only to Lat and Chl-a in August, September, October and December, while the importance of SSH was 0.026 higher than that of SST in November. In summary, Lat has the most significant influence on the forecast of South Pacific albacore fishing grounds and is an essential characteristic variable for the forecast of albacore fishing grounds; Chl-a and SST are important indicators of the abundance of albacore resources; and Lon makes a smaller contribution to the forecast of fishing grounds. The reason for this finding may be that albacore mainly grows in temperate waters, and  
Figure 8: Importance of different feature variables for the forecast of albacore fishing grounds by month in 2018–2019 based on ELM.  
temperature changes will affect the distribution of fish, while the interaction of SST and SSH may drive the intersection of hot- and cold-water masses, bringing more nutrients and attracting fish to form fishing grounds.