Causes of oyster seed (or spat) dieoffs
Use of shotgun proteomics to probe the causes of mysterious mass die-offs of oyster seed at hatcheries in Washington and Hawaii and assess implications for culture diet, water chemistry and microbes.
Steven Roberts, UW School of Aquatic and Fishery Sciences
Benoit Eudeline, Taylor Resources
Brent Vadopalas, UW School of Aquatic and Fishery Sciences
Shellfish aquaculture, especially oyster farming, is the economic mainstay of many Washington communities. But since the late 1990s shellfish hatcheries have suffered mysterious mass die-offs of oyster seed, typically about one month after fertilization. With funding from Washington Sea Grant, researchers used proteomics to investigate the factors that contribute to shellfish mortality both in hatcheries and in the wild. In particular, the scientists characterized fundamental physiological changes that occur during oyster larval development; identified protein biomarkers that indicate larval mortality events; developed a targeted assay to query specific suites of proteins; and performed the targeted assay on both hatchery and wild shellfish.
Washington State is the leading producer of farmed bivalves in the United States, providing more than $150 million in annual revenues. The industry relies on hatcheries to produce enough “seed” to distribute to growers, who then raise the shellfish to market size. However, hatchery production is a complex, resource-intensive endeavor that has been plagued with massive mortality events since the late 1990s. Gaining a better understanding of shellfish mortality could guide growers and resource managers toward stabilizing hatchery output.
Among their results, the researchers found temperature to strongly influence Pacific oyster mortality: oyster larvae reared at elevated temperatures (within tolerable range) were more likely to survive. Experiments on the influence of temperature on protein expression revealed substantial shifts in immune response for Pacific oyster larvae reared in warmer water. Different pH levels led to a shift in the microbial community, which likely played a strong role in geoduck larval survival. Olympia oyster larval and seed performance was higher when their parents were exposed to elevated pH. Hatcheries have already modified their procedures based on these and other findings from this project.