Meeting Abstract
Subtidal habitats are often assumed to harbor large bay clam populations that serve as spawning stock for intertidal populations subject to harvest. This hypothesis is rarely tested, but is used as a management principle by natural resource agencies. The Shellfish and Estuarine Habitat Assessment of Coastal Oregon project of the Oregon Department of Fish and Wildlife conducted extensive surveys of bay clam populations in subtidal and intertidal habitats of four Oregon estuaries that differ in size, geomorphology, and extent of commercial and recreational harvest. Using a stratified-random design (tide flat x tide height), bay clam population and habitat data were collected for the main intertidal flats and subtidal channels for several fisheries targeted bay clams: butter clams (Saxidomus gigantea), cockles (Clinocardium nuttallii), gaper clams (Tresus capax), littleneck clams (Leukoma staminea), and purple varnish clams (Nuttallia obscurata). Density and biomass estimates were used for an indirect test of the spawning stock hypothesis. Support for the spawning stock hypothesis was mixed. Subtidal cockles were significantly more abundant than in intertidal habitats in several estuaries. Other clam species were rare or less abundant in subtidal habitats. Bay clams are managed as a unit in Oregon and these results indicate that management may need to be estuary-specific and species-specific, especially for clams that are harvested commercially.
