In this study, the variation of seasonal and inter-annual fat content of foraging capelin (Mallotus villosus) is described. To explore long-term changes in fat content of capelin, annual fat index was made 1975 to 2012. The index was used as a response variable to see which environmental factors are likely to affect fat content of capelin such as temperature, salinity, zooplankton, biomass and large scale oceanic/atmospheric features (e.g. NAO, Blocking index). The annual fat index was also used as a predictor variable to explore if fat content can effect capelin stock recruitment and mean weight. A regression linear model showed that the only enviromental factor significantly affecting capelin fat content was the NAO index, explaining 26.1% of observed variation. The linear model also showed that the annual fat index has significant relationship with recruitment of capelin, explaining 28% of observed varitaion.