Tiny invaders threaten oyster beds
NAHCOTTA - The Willapa Bay shellfish industry has been through a lot in its more than 150-year existence - economic downturns, the dying off of the original native oyster species. But the biggest challenge today or any day for this industry is a creature about the length of a man's finger.
Burrowing shrimp, whether they be ghost or mud shrimp, have been the continued ruination of Willapa Bay oyster beds for more than 50 years. The shrimp species are native to the bay, but up until about the 1950s, they weren't much of a problem because they weren't abundant. In the late-1940s, the growers started noticing a decline in the units of oysters they were able to harvest, it was then the increase of burrowing shrimp became evident.
These shrimp species are different from other shrimp. For one, they really aren't palatable for human consumption. Secondly, rather than floating in the water, they burrow into the ground, breaking up that soil. This is a big problem for oyster growers, as valuable oyster habitat is destroyed.
So where did all these shrimp come from?
The shrimp larvae are flushed from the estuary into the sea where they grow to maturation until the tides move the adult shrimp back into the bay. There is much speculation as to why there was an increase in the shrimp population, but there has yet to be a concrete answer. One possibility includes atmospheric events like El Nino - there was one in 1957. The ocean current changes caused by this may have forced more shrimp into the bay.
"That's what people say. We don't have direct scientific evidence for these hypotheses," said Brett Dumbauld, fisheries research scientist at the Washington Department of Fish and Wildlife field office in Nahcotta. "Those are plausible things that could have happened."
Brian Sheldon, who recently ended his term as president of the Willapa/Grays Harbor Shellfish Growers Association [WGHSGA], and his family have been dealing with the shrimp problem since the get-go. Sheldon's grandfather, who held a master's degree in biology from the University of Washington, was one of the first growers to notice increasing numbers of burrowing shrimp in the bay, turning firm mud flats into sandy bogs.
"When we finally figured out it was shrimp, then the challenge was 'what can we do?'" said Sheldon.
The answer was Carbaryl, a chemical insecticide that affects the nervous system and is especially toxic to arthropods like shrimp and crabs. Oyster growers spray their oyster beds with Carbaryl, which in turn kills the shrimp in order to save the integrity of the ground. The problem is, oyster beds are prime habitat for young crabs, which are killed by the chemical.
"Most of my research suggests that those results are short term," said Dumbauld, who started his Ph.D. dissertation on ghost shrimp in Willapa Bay in 1988. "The bottom line is, if there are crabs on the beds when sprayed, it kills 100 percent of those."
But Dumbauld said that the WDFW sees the process as a tradeoff. By spraying the beds with Carbaryl, it kills off the shrimp. With the shrimp gone, the oyster beds are able to survive, thus providing the best possible habitat for baby crabs. Yes, young crabs are killed by the spray, but according to Dumbauld, the effect is not lasting. As for the other things the chemical kills, "There's no question that it kills a number of things when you spray," he said. "But most of those things have very quick life cycles."
The growers have, throughout the years, looked into other ways of controlling the burrowing shrimp populations, including crushing the shrimp burrows during low tides, compacting the soil and making it hard for the shrimp to burrow. It worked, but only marginally, and it was impossible to do on an established oyster bed because it would ruin it.
"The problem was it compacted everything and it turned it into really hard soil, and then you couldn't put anything there because when the waves came in the oysters didn't have anything to hold on to," said Sheldon.
Opponents to Carbaryl have even suggested putting plastic on the bay in order to smother the shrimp. Sure, that would work said Sheldon, but it would also kill everything else.
"Using Carbaryl is such a valuable commodity to each grower," he said. "They have a little bit they can use each year."
In 2001, the Department of Ecology issued a permit that allowed oyster growers in Willapa Bay and Grays Harbor to spray 6,400 pounds of Carbaryl over 800 acres each year for four years.
"The only options I see are either biological control or chemical control," said Sheldon.
Those options have recently gotten fewer. In April 2003, after years of legal haranguing, the WGHSGA signed an agreement with the Washington Toxics Coalition [WTC] to reduce and eventually eliminate the use of Carbaryl. The deal states that by 2012 none will be used on the bay. They also have to reduce the amount of Carbaryl used by 10 percent per year over the next three years.
Sheldon said the deal has been painted as a cooperative, friendly agreement, but for those in the Willapa Bay shellfish industry, it is anything but.
"I won't speak for our association on this - but for me, it's far from the case," he said. "Right now, the biggest challenge we have is being able to produce product. It ties back into our shrimp issues in Willapa Bay and an agreement that we were basically coerced into signing with the Washington Toxics Coalition."
On its Web site, the WTC states its mission as to "protect public health and the environment by eliminating toxic pollution ... promote alternatives, advocate policies, empower communities and educate people to create a healthy environment."
And many, both locally and statewide, who are not directly linked to the Willapa shellfish industry, believe it is good to keep chemicals out of local waters, and ask why doesn't the shellfish industry agree with that?
"To me, that's like saying 'I'm sick, but it's better to be sick than get a shot,' that's the way I look at it," said Sheldon.
The shellfish industry has been using Carbaryl on Willapa Bay since 1963, and Sheldon said as far as he is aware, there has never been any documented evidence that is bad.
"I've never heard of, or had anybody tell me - we've never had a fish kill, we've never had a bird kill, there's never been a negative impact demonstrated whatsoever!"
The WTC claims on its Web site that past use on the Willapa Bay has resulted in death of fish, crabs and other marine life that call the estuary home. Dumbauld's research supports this claim. He said that Carbaryl has been shown to kill some types of clams, worms and can have sub-lethal effects on Chinook salmon nervous systems.
"There are some fish that if caught in those tide pools [with Carbaryl in them] it will kill them," he said.
Sheldon said the reason the growers association signed the agreement was because they could no longer afford to fight the WTC in court. Sheldon said he was unable to go into too much detail regarding the agreement.
"I don't really understand all the in's and out's about what I can and can't talk about, so I'm not really going to get into it," he said, but added, "from my perspective though, I can just tell you that there's no documented evidence of any negative impact whatsoever in Willapa Bay. There's a lot of speculation."
Another part of the agreement with WTC states the growers association will spend an additional $10,000 annually over the next three years on research of alternative shrimp control methods.
What choice do they have?
"Right now, I see nothing that hasn't been tried before," said Sheldon. "I think we're just kind of reeling right now, we're not sure what we're going to do. But if we don't get a solution to control shrimp, then you're going to see this industry shrink by probably 75 percent."
One direction is biological control. Sheldon said the University of California at Santa Barbara recently did a parasitic study on Willapa Bay to see if anything already present could be used. What it found was a "parasitic castrator" in mud shrimp.
However, this was not necessarily good news, as mud shrimp are the least damaging of the two burrowing shrimp species. This parasite has somewhat stabilized the mud shrimp population. There is a similar parasite found in ghost shrimp, but it unfortunately only affects about 2 percent of the local population.
"It doesn't mean it couldn't, and it doesn't mean that there's not some real potential there," said Sheldon.
Dumbauld said it may be worth looking into the possibility of artificially enhancing the presence of that ghost shrimp parasite in order to curb the population.
"I would say we know more now than a year ago, but we're still scrambling," he said. "Chemicals were the easiest way that we knew would work."
Introducing a predatory species that may eat the shrimp is another option for biological control, including sturgeon, which used to claim higher numbers in the bay.
"Introducing an invasive species into Willapa Bay scares the hell out of me," said Sheldon. "It is such an intricate balance out in the bay. I'm not saying it can't be done, but it would take an awful lot of research to get that done."
They have also tried things like laying oyster shells on the land, which worked on a small scale. But shells are a valuable resource for oyster farmers, used for cultivating their crop and isn't the answer to the problem, either. Despite the efforts made to find an alternative, Dumbauld said they are still looking.
Sheldon said he would like to see more government agencies get involved in the research. He cited the Department of Natural Resources and its efforts to try and control the growth of spartina grass, but it is doing nothing to help with a solution to the shrimp problem.
"I find it really shocking because you have agencies that are supposed to be protecting the public trust, but what are they doing to protect that?" he said. "The public has lost thousands of acres of ground that they used to be able to get shellfish for recreation. All we hear is, 'those oyster growers are putting Carbaryl in the bay.' Well, we've been waiting for the agencies to get engaged with the problem, but to this point, there's been really nothing from them at all."
Dumbauld said he is not sure if that would really make much difference at this point, saying, "I don't know if there is enough money to solve the problem."
But if an alternative is not found soon, it could most certainly doom what we know as the Willapa Bay shellfish industry. Dumbauld said he believed it would not affect the smaller companies and private farmers so much, but rather the larger oyster companies - which also happen to employ the most people.
"I think it will definitely change the face of the industry in Willapa Bay," he said.
"I would say at this point, certainly speaking for myself, we are not giving up on chemical control in the bay," Sheldon said. "We may be backing off, but I don't see it being possible for us to maintain our production or protect our ground without chemical control."
Sheldon said if the shellfish industry is lost because of these new restrictions, the county will also lose what has been its largest employer for more than a century.
"As long as we have a healthy industry, it helps support jobs in the county. We're trying to educate the public. I just hope the public wakes up before it's too late."