Stable oxygen isotope (delta O-18) analysis of mussels (Mytilus sp.) from a 16th to mid-18th century Inuit site in southern Labrador, Canada, indicates multiple seasons of shellfish collection, and by proxy, multiple seasons of site occupation. High-resolution delta O-18 sampling of shell permits a precise season of mussel collection since the temperature and freshwater signal of the local water is retained in the shell. Live-collected specimens of Mytilus sp. obtained from Labrador, were analyzed for stable oxygen isotopes and for growth patterns. These data were used to interpret results from the archaeological shells. Growth pattern analysis was conducted to test the relationship between delta O-18 values, growth lines and shell colour. Of the two approaches, high-resolution delta O-18 sampling proved to be more reliable for determining seasonality, and showed that the Inuit at Schooner Cove harvested mussels primarily during the spring months, with some harvesting evident in the winter and autumn.