A new method could help Washington shellfish farmers control a pesky shrimp

“Burrowing shrimp make their homes deep in sediment by digging, turning the ground to Swiss cheese. This presents a problem for shellfish farmers, whose clams and oysters are often smothered under layers of displaced sediment. Shown here are people harvesting oysters in Willapa Bay in Washington. Photo: M. Barish Burrowing shrimp are small marine excavators native to Washington. They make their homes deep in the sediment by digging, turning the ground to Swiss cheese. This presents a problem for shellfish farmers, whose clams and oysters are often smothered under layers of displaced sediment. https://uw-s3-cdn.s3.us-west-2.amazonaws.com/wp-content/uploads/sites/6/2026/04/27144406/ShrimpGlass-1.mp4 The glass walls of this jar allow us to see what’s happening to the sediment as a shrimp (white) burrows. Jennifer Ruesink/University of Washington Burrowing shrimp have been a nuisance for at least a century. In 1929, Belle Stevens, a University of Washington researcher, wrote : “Oyster growers have tried various means of defense against these persistent burrowers. But there seems to be as yet no really adequate and at the same time practical method of coping with the marine ‘crayfish.'” Shellfish farmers used to use pesticides to kill the shrimp, but the chemicals also posed risks to other organisms, such as salmon and crabs, and could be transported in water outside the shellfish growing area. The Department of Ecology instructed farmers to stop using pesticides in 2018. Since then, family-owned shellfish farms have been losing large portions of their growing grounds to burrowing shrimp. Research led by the UW, and funded by the state, has yielded a non-chemical, proof-of-principle method for killing shrimp in targeted areas. The method, borrowing from the construction industry, uses a custom-built platform to apply vibration and pressure to a 50-square-foot region of sediment. This compacts the sediment and effectively traps shrimp in their burrows. Starved of oxygen, the shrimp die after a few days. The researchers tested this method at four sites around Willapa Bay, Washington. It worked just as well as pesticides, reducing the number of live shrimp by between 72% and 98%. “The challenge of managing burrowing shrimp on private tide lands has many dimensions. There still need to be enough shrimp to serve as food for gray whales and sturgeon, and the whole shrimp population is connected by a long larval phase in the ocean,” said senior author Jennifer Ruesink , UW professor of biology. “Once back in the estuary though, these shrimp can live for up to 10 years. Even a moderately sized shrimp, about four inches long, can bring a handful of sediment to the surface every day, dropping that on top of everything. We’re trying to find the balance — how to keep them out of shellfish beds, but let them grow elsewhere.” The team published this research May 12 in the Journal of Shellfish Research. “Burrowing shrimp have decimated our farm,” said Ken Wiegardt, a fifth-generation oyster farmer and head of Jolly Roger Oysters in Willapa Bay. “We’ve lost 75% of our nursery ground and, as a result, the farm’s carrying capacity has fallen from 265,000 bushels of market-ready oysters to 75,000 bushels. Last month I had to lay off three oyster shuckers, each of whom had been with me for many years, because I just don’t have the oysters to process. The health of the Willapa Estuary as well as my business and all of my employees depend on finding an effective tool.” Over the years farmers and researchers have toyed with the idea of trying to “mechanically” control shrimp populations. “The idea was, ‘Let’s crush them underground, or crush them when they come to the surface,'” Ruesink said. “There are old photographs that show people using vehicles, such as repurposed tanks and snow crawlers, to try to target the shrimp.” This idea resurfaced at a recent conference. Over lunch, Ruesink and shellfish growers decided to codesign an experiment to test whether driving a tracked vehicle called a MarshMaster over sediment would actually affect the shrimp . After careful analysis, the method proved ineffective. Ruesink’s co-author, Alan Trimble, who was previously a research scientist at UW and is now volunteering on this project, had an idea for why the “crushing” experiment had failed. “He told me, ‘You’re thinking like a dirt farmer and you need to start thinking like a concrete engineer instead,'” Ruesink said. “That’s when he mentioned these concrete vibrators in construction. When you pour concrete, if you don’t get all the bubbles out of it, it won’t be as strong. This is a consolidation technique for a wet slurry of particulates, which is exactly what a mud flat is.” Ruesink and Trimble ran three experiments to test whether a concrete vibrator, a hand-held metal tube with a motor powered by a generator, could kill the shrimp. For each experiment the team compared sediment cores from treated plots to cores from untreated plots. The researchers took core samples on multiple days after treatment and counted live versus dead shrimp. https://uw-s3-cdn.s3.us-west-2.amazonaws.com/wp-content/uploads/sites/6/2026/04/27145606/IMG_2661-1-copy.mp4 In an earlier experiment, the team tried using the vibrator while standing in the water. This method was successful in killing shrimp, but also not practical for scaling up. Jennifer Ruesink/University of Washington The best option was a custom-built floating platform with six vibrators mounted through a hollow part in the middle. Ruesink and Trimble added weights near each vibrator head to provide pressure in addition to vibration, a winning combination that compressed the sediment and killed the shrimp. The specific cause of death was asphyxiation, not the vibration. The custom-built floating platform (shown here) allowed the researchers to apply vibration and pressure to a specific region of sediment. The hollow part in the middle of the platform allows six concrete vibrators to compact the sediment below, which kills the shrimp by starving them of oxygen. Photo: Jennifer Ruesink/University of Washington While this proof-of-principle experiment seems promising, there’s more work to do before shellfish farmers can implement it. Right now it’s a time-consuming and labor-intensive process because everything is manually operated. Also, more studies need to be done to determine the long-term impacts to the ecosystem, from the shrimp in neighboring non-shellfish farm mudflats to other creatures living in the area. “What we’ve done so far is introduce a novel control mechanism. No one had thought that you could trap the shrimp underground,” Ruesink said. “But this research wouldn’t have happened without the investment from the state and the private landowners and growers. I have such a deep appreciation for the opportunity to work with folks on something that is clearly affecting their lives.” The researchers performed field trials on the private tidelands of Pacific Shellfish, Bay Center Farms and John Heckes. This research was funded by the Washington State Department of Agriculture. For more information, contact Ruesink at ruesink@uw.edu . For more information about Jolly Roger Oysters, contact Wiegardt at oysterman73@hotmail.com .

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