Abstract <p>The results of a study of the biology of the soft-shell clam <i>Mya arenaria</i> in the intertidal zone of the Murmansk coast of the Barents Sea are provided. Settlements are represented by the soft-shell clam with the shell length varying 15.5 to 84.2 mm and ages of three to ten years old, with a prevalence of middle age groups (6–8 years). The study areas are found to have soil composed of uneven grains of sands with different proportions of an admixture of both coarse gravel fractions (up to 62.5%) and fine silty and pelitic fractions (up to 74.6%). The dependence of the shell shape on the soil type was analyzed. Mollusks on silty sand with a content of pelite fractions from 4.7 to 7.0% had the largest body size and weight. The values of the coefficients of allometric growth were revealed to decrease with a change in the soil type from sand to sandy silt.</p>