Rapid Response Network

Coordinated by Ashleigh Epps, Washington Sea Grant; Rana Brown, Squaxin Island Tribe; and Julieta Martinelli, Washington Department of Fish and Wildlife

About the Network

Shellfish have been an integral part of the life of Washington state Tribes for millennia, and for residents and visitors alike. The shellfish aquaculture industry in Washington State is the largest in the nation, generating 150 million in annual farmed bivalve sales. Over the past century, shellfish have transformed the state’s economic landscape, creating thousands of jobs in coastal communities. Additionally, shellfish provide an important ecological role to the surrounding ecosystems.

In June 2021, the region faced an unprecedented climatic event that led to high mortality in many shellfish species. An atmospheric heatwave coincided with the lowest low tides of the year (June 26-28, 2021), exposing intertidal and subtidal invertebrates to unusually high air temperatures. These anthropogenic changes (i.e., warmer ocean and air temperatures) are expected to persist and increase in frequency and intensity, suggesting that the threats that extreme weather events pose to shellfish are likely to continue.

Therefore, there was a need to create a Rapid Response Network for resource managers and shellfish industry members to prepare and stay uniformly informed about potential upcoming climate-induced shellfish mortality events. This also includes creating a Rapid Response Plan that aims to develop standardized sampling recommendations that can be used to both: (1) monitor non-harvest beaches to obtain baseline data; and (2) detect changes to shellfish communities over time due to climate-driven events.

Takeaways from the 2021 mortality event

• Coastal sites largely avoided negative impacts due to increased wind and wave action compared to inner Puget Sound sites that are more protected.
• Manila and native littleneck clams varied in observed conditions.
• Olympia oysters, which tend to reside in the lower coastal zone, were less affected than Pacific oysters.
• Pacific oysters were in poor condition in more southerly latitudes.
• Species in the higher intertidal zones, such as barnacles, were in much worse condition than those found in the lower intertidal regions.
• Species that could burrow further into the sediment (>15cm) were observed to be in better condition (i.e., butter clams) than those that burrowed shallower in the sediment (i.e., cockles).
• Mortalities continued to be observed weeks after the event, likely due to prolonged heat stress.
• Many of these species were likely reproductive at this time, which has resulted in decreased adult populations in some locations.

Observed climate-induced mortalities from 2021-present

Rapid Response Plan

Rapid Response Plan: Coming Fall 2025

Suggested priority species for surveys:

• Manila clams (Venerupis philippinarum)
• Native littleneck clams (Leukoma staminea)
• Butter clams (Saxidomus giganteus)
• Cockles (Clinocardium nuttallii)
• Razor clams (Siliqua patula)
• Macoma clams (Macoma spp.)
• Pacific oysters (Crassostrea gigas)

Rapid Response Methods

1) Rapid survey developed by Swinomish Indian Tribal Community (SITC) (Note: cockle surveys only)

• Use a GPS unit to walk the rough perimeter of the mortality area.
• Select 2-3 areas to carry out a 50 m transect line
• For each transect count all dead shells 1 m to the right, and 1m to the left of the transect. Think of this as a giant 2*50 m quadrat.
• Repeat for as many 50 m transects as you can.
• Use the transect calculation to estimate number of dead shells per m2, and for the total area estimated in the perimeter.

Example table that can be used for this method:

2) Semiquantitative method based on Raymond et al. (2022)

Google form to gather these data from scientists: SHELLFISH MASS MORTALITY RAPID SURVEY

For observations of large numbers of dead or dying invertebrates (e.g. after a series of very hot days, you visit your local beach or private tideland and notice a large number of dead oysters with their shells separated and gaping open).

Raymond et al. (2022) used a Post Heat Wave Rating (PHWR) survey to assess shellfish condition using a semi-quantitative rating scale. Scientists had to possess extensive local knowledge of a site in order to submit information. Their expert knowledge was used to assess what they were seeing relative to what they would consider typical based on their prior experience with specific sites and species at the same time of year.

Experts rated the condition of the animals according to the following scale:

1 = much worse than normal

2 = worse than normal

3 = normal

4 = better than normal

5 = much better than normal

3) Washington Department of Fish and Wildlife (WDFW) – Reporting Tool

Link to the reporting tool: SHELLFISH MASS MORTALITY REPORTING TOOL

For commercial shellfish growers: the shellfish and marine invertebrate mass mortality reporting tool helps WDFW understand how industry is impacted by these events; however, please note that this reporting tool does not supersede reporting requirements established as part of transfer permit conditions.

References

1. United States Department of Agriculture, National Agricultural Statistics Service. 2023 Census of Aquaculture. 2025.
2. Raymond WW, Barber JS, Dethier MN, Hayford HA, Harley CDG, King TL, Paul B, Speck CA, Tobin ED, Raymond AET, McDonald PS. Assessment of the impacts of an unprecedented heatwave on intertidal shellfish of the Salish Sea. Ecology. 2022 Oct;103(10):e3798. doi: 10.1002/ecy.3798. Epub 2022 Jul 27. PMID: 35726191; PMCID: PMC9786359.
3. Raymond, W. W., Tobin, E. D., Barber, J. S., Hayford, H. A., Raymond, A. E., Speck, C. A., Rogers, D., & Brown, R. (2024). Short-term effects of an unprecedented heatwave on intertidal bivalve populations: Fisheries management surveys provide an incomplete picture. Frontiers in Marine Science, 11, 1390763. https://doi.org/10.3389/fmars.2024.1390763

The Rapid Response Network is in collaboration with University of Washington, Taylor Shellfish, Jamestown SK’lallam Tribe, Puget Sound Restoration Fund, Swinomish Indian Tribal Community, Skokomish Indian Tribe, Evergreen State College, and NOAA National Marine Fisheries Services.