Relative abundance index is often used to measure the level of fisheries resources biomass.Based on chub mackerel(Scomber japonicus)catch data of the large lighting-purse seine fishery from 1999 to 2011,the impacts of temporal(Year,Month),spatial(Longitude,Latitude),environmental factors(Sea surface temperature,Sea surface height and Sea surface chlorophyll-a concentration)and fishing performance(Vessel name)on catch per unit effort(CPUE)were analyzed using generalized linear model(GLM)and generalized additive model(GAM).The Year effect of CPUE,extracted from GAM,was used as the annual abundance index(AI)to reflect the inter-annual variation of chub mackerel abundance in the East China Sea and Yellow Sea.The relationship between AI and SST in the chub mackerel spawning ground and fishing effort was also investigated.The GAM with the eight variables explains 11.69% of the total variance in nominal CPUE,and the impact of Year on CPUE is the foremost factor,contributing to 53.9% of the total reduction in deviance.The extracted Year effect indicates that chub mackerel abundance shows a declining trend over the past 13 years,especially after 2008,and the AI fell from 1.22 in 2008 to 0.82 in 2011.The AI shows a significantly positive relationship with the SST of the spawning ground,and it is expressed as AI=-3.5+023SST(P<0.05).This result indicates that SST of the spawning ground has a positive impact on the abundance of chub mackerel.The decrease of chub mackerel abundance in the East China Sea and Yellow Sea resulted from the rapidly increasing number of purse seine vessels in the recent years.