Burrowing shrimp control
In saltwater tidal areas, two native burrowing shrimp species live in the muddy areas near the shorelines (mud shrimp, Upogebia pugettensis and ghost shrimp, Neotrypaea californiensis). In Willapa Bay and Grays Harbor where the tide goes out exposing the mudflats, shellfish farmers grow oysters in the same area where the burrowing shrimp live. Sometimes the shrimp population increases so much that the mud becomes too soft and the farmed oysters will sink, smother, and die. Controlling excess populations of burrowing shrimp on commercial shellfish beds in Willapa Bay and Grays Harbor started in the 1960’s.
You can find all of the previous permit documents in our permitting database (PARIS)
Integrated Pest Management Plan and Working Group
In 2018, Ecology denied the water quality permit for the Willapa Bay and Grays Harbor Oyster Growers Association (WGHOGA) to use imidacloprid to control burrowing shrimp. The permit denial was appealed and Ecology negotiated a settlement to work collaboratively developing an Integrated Pest Management (IPM) plan. The 2019 settlement agreement established the working group and several extensions continue the work.
The Integrated Pest Management Plan states the Working Group must identify integrated non-chemical and chemical methods to control burrowing shrimp. The Washington State Department of Agriculture (WSDA) awards and administers the funds while the Working Group oversees research grants awarded to study shrimp control methods and tools. Since 2020, the IPM Working Group meets regularly to discuss progress and hear from researchers who are developing the various tools. To date, testing and research have not identified a viable and effective pest management solution or suite of tools.
The IPM Working Group consists of representatives from the Washington Departments of Ecology, Agriculture, Fish and Wildlife, and Natural Resources, along with the Conservation Commission, Washington State University, Pacific Shellfish Institute, Sea Grant, Shoalwater Bay Indian Tribe, shellfish growers/processors, and, at times, local environmental groups. We participate and offer expertise in water quality, sediment ecology, and aquatic toxicology to guide research to protect aquatic life and beneficial uses.
To learn more about current and past research, visit IPM Working group website.
History of burrowing shrimp control
- From the 1960s through 2013, carbaryl (sold as Sevin) was used on commercial shellfish beds. A water quality permit for use of this pesticide was in effect from 2002 through 2013.
- To phase out carbaryl use, alternative management approaches were tested from 2001 through 2014 following an Integrated Pest Management Memorandum of Agreement (MOA) between several shellfish associations and state agencies.
- From 2008 through 2014, experimental trials of a neonicotinoid pesticide called imidacloprid were done.
- Oyster growers applied to Ecology for a water quality permit to use imidacloprid to control shrimp in 2013.
- In 2015, we issued a permit for shrimp control, however before it became effective the growers withdrew their application. While the permit was highly conditioned for limited imidacloprid use, based on the growers request, we terminated the permit.
- In 2017, the growers applied again for use of imidacloprid to control the shrimp and in 2018 Ecology denied the permit resulting from new science on neonicotinoids’ impacts to non-target species.
- In 2019, the permit denial was appealed, and a settlement was developed with WGHOGA to collaborate on developing an Integrated Pest Management (IPM) plan.
- Under the IPM Plan, an IPM Working Group guides research and meets regularly with researchers to help develop the various methods to control burrowing shrimp.
2018 permit denial for Imidacloprid use
In 2017, for a second time, shellfish growers from Willapa Grays Harbor Oyster Growers Association (WGHOGA) requested a water quality permit to use Imidacloprid. This request included applications for a water quality pollution discharge (NPDES) permit and two sediment impact zones. This new permit application went through the full regulatory process. This process includes three phases: review of the environmental impacts, a decision on whether to develop a permit, and the permit development process.
There were key differences between 2017 and the original permit application in 2015, including a considerable amount of new science. During Ecology’s environmental review, we reviewed many new scientific data and research studies on neonicotinoid pesticides and assessed more than 8,000 public comments. Based on the new science, we determined the 2017 application and proposal could not meet Washington's environmental sediment and water quality protection laws. On Sept. 27, 2018, we finalized the denial of the permit.
Reasons for denial included:
- Significant, unavoidable impacts to sediment quality and benthic invertebrates.
- Negative impacts to juvenile worms and crustaceans in areas treated with Imidacloprid and nearby areas covered by incoming tides, including high mortality for Dungeness crabs.
- Negative indirect impacts to fish and birds caused by killing sources of food and disrupting the food web.
- Concern about non-lethal impacts to invertebrates in the water column and sediment.
- A risk of impacts to invertebrates from imidacloprid even at low concentrations.
- Increased uncertainty about long-term, non-lethal, and cumulative impacts.
You can find all of the permit documents in our permitting database (PARIS)
Contact information
Laurie Niewolny
Aquaculture Permit & Water Quality Specialist
Laurie.niewolny@ecy.wa.gov
360-584-8852