The stakes are high. The shellfish industry represents well over $60 million to the state’s economy.
Oyster grower Dick Wilson can hold one of the biggest threats to his livelihood in the palm of his hand-a pink, gnarly, destructive, burrowing shrimp.
Two indigenous species of burrowing shrimp-ghost shrimp and mud shrimp-are taking a serious toll on shellfish farms in Willapa Bay and Grays Harbor. Ghost shrimp turn the usually firm, underwater substrate upon which oysters and clams are grown into the consistency of quicksand, according to Wilson. That leaves the cultivated shellfish to literally sink and die. Mud shrimp build a static, U-shaped burrow. When they reach high population densities, they too can soften the substrate, while filtering out the same plankton shellfish and other organisms eat.
“This is very much an Achilles’ heel of the industry,” says Wilson, who has grown oysters on Willapa Bay for the past quarter century. “Natural predators include sturgeon, sculpin, and flat fish, but what have we done to our fish? Helped them disappear. If we can’t control burrowing shrimp, I’m pessimistic about the future of the entire shellfish industry in Washington.”
And soon, oyster farmers will be fighting the battle against burrowing shrimp without their most effective tool to date-carbaryl. In an effort to avoid expensive legal battles with environmental groups opposed to the pesticide, growers already are reducing their use of it and have agreed to voluntarily stop using it altogether by 2012.
Growers first started using carbaryl to manage burrowing shrimp in the 1960s. According to Kim Patten, director of the Washington State University Research and Extension Unit at Long Beach, it was effective and did not have any long-term deleterious effect on the estuary’s ecosystem. A single application was enough to protect the commercial oyster beds for up to four to eight years. Still, some objected to the use of the pesticide to control a native species in an estuary.
So what will take carbaryl’s place? No one knows, Patten says.
“Do we have any tenable solutions in sight? The answer is ‘No, we don’t,'” he says. “Management alternatives are being developed that can be used in some beds under some conditions, but none that serve as a broad replacement for carbaryl. We have a long way to go.”
Fortunately, Patten says, new funding from the Washington legislature and the federal government is being used to pull together a team of scientists, engineers, and growers to address the burrowing shrimp problem. More than a quarter million dollars will be invested annually.
The 17-member team, led by WSU, includes professionals from four universities, two federal agencies, and two private institutions, including the Willapa Bay/Grays Harbor Oyster Growers Association and McGregor Co., an agricultural engineering and chemical firm based in Colfax. “What’s exciting and different from previous efforts to address the problem is that we are getting a lot of new people involved, people that never would have been players before,” Patten says. “It’s such a difficult problem that we really want to make sure we have some outside thinking.”
Wilson agrees. “I’ve spent 25 years as a scientist and an oyster grower, and finally, everyone in the industry is working together to solve the problem. We realize we can’t play anymore.”
The team will attack the issue on a variety of fronts. They’ll develop a comprehensive program to map the shrimp’s development between the larval stage and adulthood. They’ll look at new mechanical ways to inject chemicals deep into the substrate and/or physically remove burrowing shrimp.
They’ll look into alternative chemical controls as well. They’ll study the ecological consequences of any new chemicals that are advanced for control. They’ll examine the reintroduction of natural predators, such as fish and crab. And they’ll look at managing the parasites that naturally occur in burrowing shrimp and use them as a biocontrol agent.
“This is unquestionably one of the most complex and difficult pest management issues in the state, and I doubt that there will be one single solution,” Patten says. “But there are some things that look like they have some potential.”
The stakes are high. The shellfish industry represents well over $60 million to the state’s economy. Shellfish aquaculture ranks just behind the timber industry in terms of the number of jobs it creates in rural, coastal counties like Pacific County. Oyster cultivation has been proven to be an environmentally positive, sustainable activity in coastal estuaries.
Currently, there are about 100 shellfish farms in the region, ranging from small, family-run businesses to large corporate operations. Eliminating the use of carbaryl without a new way to control burrowing shrimp could have dramatic economic consequences.
“To illustrate the economic impact of the ban on carbaryl, we only need to look at an example from Oregon,” wrote the team in its original proposal. “Carbaryl was banned in Tillamook Bay, Oregon, in 1985, and within six years, production had dropped 80 percent.”
Kathy Barnard is the senior public relations specialist for WSU Extension.