Mounting evidence affirms decision of Ecology to deny use of pesticide in shrimp farms – WA Dept of Ecology

The Department of Ecology has denied a request by oyster growers to use a pesticide called Imidacloprid on shellfish beds in Willapa Bay and Grays Harbor. This little known issue exploded into the open a few years ago when a scientist for the Department of Ecology, Rich Doenges, the water-quality manager for the state Department of Ecology signed off on use of the chemical even though the instructions for it clearly stated

“This product is highly toxic to aquatic invertebrates. Do not apply directly to water, or to areas where surface water is present or to intertidal areas below the mean high water mark.”

Ecology noted the following environmental impacts as key reasons for denying the permit:

  • 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 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 from imidacloprid even at low concentrations.
  • Increased uncertainty about long-term, non-lethal, and cumulative impacts.

This will have significant effects on shellfish farmers in the two major bays on the west coast of Washington State. Some shellfish farmers may lose their farms over this decision. There are no known alternatives to kill the shrimp.

It has been claimed that this problem was caused by the introduction of the Columbia River dams in the 40s and beyond. Originally the plume of the river’s outflow of fresh water kept the shrimp under a natural control. With the lack of fresh water the shrimp were able to move into the bays and not have a natural control on their expansion.

The controversy was highlighted in a 2017 story on KNKX radio.

Also more background on the controversy was reported in the Seattle Times.

and also in this Seattle Times story:


After considering and responding to more than 3,000 public comments, the Washington Department of Ecology has finalized its decision to deny the use of imidacloprid on shellfish beds in Willapa Bay and Grays Harbor. Mounting scientific evidence confirms the harm from this neonicotinoid pesticide poses too great a risk to Washington’s environment.

Shellfish growers from the Willapa-Grays Harbor Oyster Growers Association requested a permit from the state to spray imidacloprid on oyster and clam beds to control native burrowing shrimp. Ecology tentatively denied the request in April pending the evaluation and response to public comments.


One Response

  1. Has anyone considered harvesting the shrimp as a control on their population? It might create jobs, control the problem, and be another protein source.

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