We developed a new approach for evaluating energy dynamics in fish populations and applied it to largemouth bassMicropterus salmoides.Wild fish were collected monthly and primary energy constituents (protein and lipid) were determined for specific tissues (muscle, liver, and gonad). Monthly samples were partitioned into length categories, and sex-specific log10weight-length regression equations were used to predict weights for the midpoint total lengths of stock to quality (S-Q) and quality to preferred (Q-P) length categories (250 and 340-mm TL for S-Q and Q-P fish, respectively). These weights then were adjusted by using the monthly relative weight (Wr) means of sex and length categories as correction factors to adjust for seasonal changes in plumpness to arrive at a representative monthly weight for each category. Monthly lipid and protein fractions of tissues then were multiplied by mean muscle, gonad and liver weights of these standard fish to obtain lipid and protein weights. Energy equivalents were applied to provide total energy estimates of the lipid and protein quantities. The approach provided a unique method for evaluating population energetics allowing direct comparisons among sex and length categories.