The ecological and ethnological aspects of the harvesting of the cockle, Leukoma pectorina (Bivalvia: Veneridae), were investigated on Algodoal-Maiandeua Island, on the Amazon coast of Brazil. Ethnobiological data were collected through informal conversations, semi-structured interviews, and observations of the harvesting and processing of bivalves on the island. Following the ethnobiology study, the cockle beds were surveyed to evaluate the density of L. pectorina, body size and the meat yield of the cockles in the months of dry and rainy seasons. In the study area, cockling is a manual and artisanal activity, and L. pectorina is typically harvested by mothers with little formal education. The cocklers make their own tools, cockles are prepared in the family environment, and the majority of the catch is sold to commercial establishments on the island. Cockling is a sporadic activity used to complement the family income, and is more common during the dry season, when tourism increases on Algodoal-Maiandeua Island. The cockles are also larger and population density is higher during this season, and the cocklers themselves recognize this period as providing the most productive harvest. These fi ndings reinforce the value of traditional knowledge for both scientifi c research and the planning of the management of coastal fi shery resources.