We report on the diet dynamics of a population of largemouth bass (Micropterus salmoides) over a 30 year period (1980-2010) in Michigan's Upper Peninsula, USA. Paul Lake is a small, unexploited, north temperate lake. We used seven functional diet groupings to assess inter-annual diet dynamics: zooplankton, Chaoborus spp., benthic invertebrates, pelagic invertebrates, terrestrial insects, fish prey and terrestrial vertebrates. To measure annual diet fluctuations an annual composite Index of Relative Importance, IRI (based on Σ of % number, % mass and frequency of occurrence of each diet grouping) was employed. We chronicled diets of 5098 largemouth bass. Significant inter-annual variation (Z ± 1.96, p < 0.05) occurred in each of the seven functional diet categories (variance ranged from 24-59%, 7/30 years and 17/30 years, respectively, of the entire data set). Those diet categories which had the fewest significant differences in annual IRIs as compared with the 30 year composite IRI value were zooplankton and terrestrial vertebrates at 24% and 34% (10/30 years). Fish prey and Chaoborus spp. had the most significant inter-annual variations at 55% (16/30) and 59% (17/30 years), respectively. The variance of the remaining diet functional groups ranged from 33-47% (10 to 14/30 years). We addressed the question of inter-annual diet fluctuations in relation to bass population density changes, but principle component analysis (PCA) demonstrated no correlation between diet and bass density (r = −0.030, p > 0.850).