15-25 individual blue mussels (Mytilus edulis) were randomly sampled at each of the major mussel beds (stations) along the eastern Maine coast from Frenchman Bay to the Canadian border. Sampling reflected the existing size frequency distribution of mussels within each bed, but was truncated at a minimum shell length of 25 mm to ensure mussels were of reproductive size. For each individual mussel, sample processing consisted of measuring the shell length (0.1 mm resolution), and then dissecting out the gonad and somatic soft tissue separately. Gonad and somatic soft tissues were weighed separately to 0.01 g resolution. The gonad index of each individual mussel was calculated from the two measured weights (Gonad Soft Tissue Weight, Somatic Soft Tissue Weight).