Relationship between catch rate of longline albacore (Thunnus alalunga) and environmental factors in South Pacific

Based on the data of albacore logbook (Thunnus alalunga) collected by mainland China from 2015–2017 in the South Pacific and the marine environmental data in the same period, we analyzed the relationship between catch rate and environmental factors, so as to examine the effects of environmental factors at different depths on T. alalunga by establishing a GAM (Generalized additive model). In addition, we had obtained the correlation coefficient of each environmental factor (those with large correlation were grouped and modeled) by correlation analysis. The results show that: 1) Sea surface temperature and sea temperature at depth of 120 m, sea surface temperature and sea surface height, sea temperature at depth of 120 m and sea surface height, sea temperature and sea salinity at depth of 300 m were highly correlated factors. However, sea surface salinity, chlorophyll a concentration and northward sea surface wind had no significant correlation with the other environmental factors. 2) The explained cumulative deviance was 30%–40%; the environmental factors sorted by importance are as follows: sea temperature at depth of 120 m, sea surface temperature, sea temperature at depth of 300 m, sea salinity at depth of 120 m, sea surface height, sea salinity at depth of 300 m, sea surface salinity, mixed layer depth, northward sea surface wind, eastward sea surface wind and chlorophyll a concentration. 3) The sea temperature at depth of 120 m was negatively correlated with CPUE (Catch per unit effort) at 15–30 ℃. The trend of sea surface temperature was similar to the sea temperature at depth of 120 m, with a positive correlation at 25–28 ℃. The sea temperature at depth of 300 m and CPUE showed a significant positive relationship at 10–18 ℃.