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, for residents and visitors alike. The shellfish aquaculture industry in Washington state is the largest in the nation, generating 243 million in annual farmed bivalve sales in 2023. Over the past century, shellfish have transformed the state’s economic landscape, creating thousands of jobs in coastal communities. Additionally, shellfish perform important ecological and cultural roles in 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), 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 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 effort 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

• Pacific Coast sites in WA largely avoided negative impacts due to increased wind and wave action compared to the Salish Sea sites that are more protected.
• Olympia oysters, which tend to reside lower in tidal elevations, were less affected than Pacific oysters.
• Pacific oysters suffered higher mortality and stress in more southern locations.
• Species in higher intertidal zones, such as barnacles, were in much worse condition than those found in lower intertidal regions.
• Species that could burrow further into the sediment (> 15 cm), such as butter clams, were observed to be less stressed than those that burrow shallowly in sediment, such as cockles.
• Mortalities continued to be observed weeks after the event, likely due to prolonged heat stress.
• Many of the individuals who died were likely preparing to reproduce at the time of the heatwave. This decreased larval supply could result in lower shellfish populations several years after the heatwave.

Observed climate-induced mortalities from 2021-present

Rapid Response Plan

Rapid Response Plan: Coming Fall 2025

Suggested priority species for surveys (proposed methods can be used for other species and may have to be adapted for these species listed):

Rapid Response Methods

1) Rapid survey developed by Swinomish Indian Tribal Community

In 2024, the Swinomish Indian Tribal Community (SITC) trialed a survey method to estimate cockle loss following a significant mortality event that resulted in thousands of dead cockles on the surface of a beach. This newly designed method allowed staff with the SITC Fisheries Department to rapidly estimate the number of recently dead cockles. Using the area (acreage) of the mortality event and the estimated mortality/m2, we were able to estimate the loss within the zone of the event. These methods are easily reproduced and can be utilized by any co-managers desiring to roughly estimate the number of bivalves lost.

Method:

1. Assign one surveyor to take a GPS unit and walk, while tracking, the perimeter of the mortality area. All transect methods deployed in the following steps occur solely within this perimeter.
   • Back at the office, this perimeter can be uploaded into ArcGIS to estimate the acreage of the event.
2. Depending on the size of the mortality area, plan to deploy transects perpendicular to the shoreline evenly throughout the region to obtain thorough coverage. As a hypothetical example, if the perimeter is 1,600 m wide, managers may wish to deploy eight transects every 200 m. If time is running short, managers could do four transects every 400 m instead. Fewer transects equate to higher error, but this method should ideally only be used for a fast and rough estimate of mortality, regardless.
   • Transects should run from the upper elevation to the lower elevation of the mortality region and extend the width of the perimeter.
3. Have two surveyors stand on either side of the transect tape holding a 1 m bar in their hands. One surveyor counts all the dead cockles on their side of the line, while the other surveyor counts all the dead cockles on the other side of the line from the beginning to the end of the line.
   • Record the length of the final transect to determine the area surveyed on that particular transect.
   • For example, if your line was 60 m long and you had two surveyors, one on either side, your surveyed transect area was 60 m * 2 m = 120 m².
4. Back at the office, calculate the number of dead cockles/m² on each transect based on count data and obtain a mean # of dead cockles/m² across all transects.
5. Multiply the area of the entire mortality region by the mean number of dead cockles/m² to obtain a rough estimate of the total loss.
   • For example, if you have a mortality area of 600,000 m² and 0.8 dead cockles/m², you will estimate that 480,000 cockles died.
   • Managers interested in obtaining a biomass loss estimate could also collect a subset of dead cockles to measure and use published length-weight estimates (see Bradbury et al. 2005 or Barber et al. 2012 appendix) for cockles to determine biomass loss.

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.