Carolyn S. Friedman, University of Washington, School of Aquatic and Fishery Sciences
Brent Vadopalas, University of Washington, School of Aquatic and Fishery Sciences
Under legislative mandate, Washington Sea Grant undertook a large-scale, six-year multidisciplinary study of the ecological and biochemical effects of geoduck planting and harvest. Over the course of three years, Washington Sea Grant-supported researchers sampled and screened hundreds of randomly collected wild geoduck from three Puget Sound sites. In 2012 they conducted in-depth statistical analyses, seeking to understand seasonal and geographic influences on parasite occurrence.
A lack of baseline data on geoduck health, parasites, and diseases has hindered management of this valuable shellfish, making it difficult to identify potential pathogens. This in turn made it more difficult to trace the causes of disease, determine whether endemic or newly introduced microorganisms may be involved, and anticipate the effects of seasonal and environmental factors.
The study developed baseline information on pathogens to improve understanding of geoduck health and management of both wild and cultured stocks. The samples revealed several parasites previously unreported in geoduck, including the first molluscan microsporidian identified in the Pacific Northwest. The parasites’ presence correlated with season and location, but varied among species in relation to water depth. The two most common parasites, a Rickettsia-like organism in the gill and a metazoan in the siphon, occurred most often in summer, although metazoan trends varied among sites. A Steinhausia-like organism had a tendency to to occur in winter and spring when the clams mature reproductively. Another microsporidian-like organism occurred in all seasons. Preliminary molecular analyses suggest it will be possible to definitively identify geoduck parasites and develop diagnostic tools to screen for them. This will help state and tribal resource managers respond to outbreaks and plan stock transfers and farm sitings.
For more information, see the Geoduck Aquaculture Research Program final report.