Shellfish monitoring has been accepted by the Pacific Bioregion of Parks Canada as a measure of ecosystem health in soft substrates in the intertidal zone. Surveys are used to capture the status of selected bivalves within the national park reserve to determine long-term population numbers and trends in response to natural and/or human disturbance. Shellfish surveys are completed annually in May at selected sites in the Broken Group Islands Unit of Pacific Rim National Park Reserve. Clam and oyster datasets are presented separately, as surveys follow different field protocols, but both use variations of a method of randomly selected quadrat sampling along a transect. Surveys follow the principle of non-destructive sampling and protocols, developed in collaboration with fisheries biologists, and are based on stock assessment methods applied coast-wide by Fisheries and Oceans Canada. Intertidal bivalves are good indicator species of the overall environmental conditions of an area because they are relatively long-lived and spend the majority of their lifespan in one location. Furthermore, shellfish populations remain vulnerable to over harvesting by a variety of users (including legitimate recreational harvesters) in the Park Reserve.