Category Archives: Shellfish

Are we at a crossroads in the green crab invasion on Dungeness Spit?

State biologists are holding out hope that the European green crab invasion at Dungeness Spit can be contained. We may now be going through a critical period, which could result in a permanent infestation or possibly the final throes of the invasion.

Green crabs, an invasive species known to displace native species and cause economic devastation to shellfish growers, were first discovered on April 12 in a marshy area on Graveyard Spit, which juts off from the larger Dungeness Spit in the Strait of Juan de Fuca.

The total number of green crabs caught in an ongoing intensive trapping program has reached 76. The weekly numbers have been declining, as shown in a chart on this page. That could be a good sign, but biologists are quite reserved in their predictions.

“The numbers are tapering off,” said Allen Pleus, coordinator of the state’s Aquatic Invasive Species Program, “but in my view the numbers are still too high. Eradication would take several weeks of zero. At this point, our main objective is to bring down the population to a point where spawning would not be successful.”

So far, all of the crabs caught are young and small — about 1 to 2.5 inches across their backs. This means that they have not been in the area for long, probably arriving on last year’s currents in the Strait of Juan de Fuca.

Another good sign is that no other crabs have been caught elsewhere along the Strait, although officials acknowledge that they would like to deploy more traps to capture any early invaders. Also, I am happy to report that no new crabs have been captured this year in Padilla Bay or on San Juan Island, where the state’s first confirmed green crab invasion took place last year. See Water Ways, Sept. 24, 2016.

Update: I’ve been informed that one green crab was caught in April in Padilla Bay where others were caught last year.

The decline in captures at Dungeness Spit may be a sign that some of the crabs have entered their reproductive phase, a period when they don’t eat and so are not attracted to the baited traps. Males and females get together to mate after molting, a phase of development in which they shed their exoskeletons. The trapping effort has reduced the crab numbers and made it more difficult for reproductive males and females to find each other, but each female can produce hundreds of thousands of eggs — so even one successful mating could expand the invasion.

This small male crab is one of the 76 European green crabs caught in traps at Dungeness Spit. // Photo: Allen Pleus

Because the baited traps may not work at this time, officials are experimenting with substrate traps, which are pieces of plastic pipe ranging in size from a half-inch to 2 inches, Allen told me. Young crabs may seek shelter in the tubes. So far, no crabs have been captured that way.

Another idea yet to be tried is baiting traps with pheromones, which are sexual attractants that lure crabs looking for a mate. Allen said he also would like to experiment with electrical stimulation, in which an electrical current is discharged in the muddy substrate to drive crabs out of their burrows. With proper control, no permanent harm comes to them or other creatures in the vicinity, Allen said.

When it comes to controlling future crab invasions in Puget Sound, experts would like to know where the crab larvae are coming from. The leading suspect is a population of green crabs that appear to have settled into Sooke Inlet, just west of Victoria on Vancouver Island in Canada. It is also possible that the larvae drifted in from coastal waters in British Columbia, Washington or even Oregon or California. Experts hope that genetic tests of green crabs from the various locations can be used to identify where the crabs on Dungeness Spit originated.

Emily Grason of Washington Sea Grant coordinates a group of volunteers who monitor traps placed throughout Puget Sound with a goal of stopping the next invasion.

“The presence of green crab in Dungeness Bay, though unfortunate, offers a unique opportunity to test how effective the EDRR (Early Detection-Rapid Response) model is for intervening in a potential green crab invasion,” Emily wrote yesterday in a blog post on the Crab Team website.

“Generally speaking, invasive species are rarely noticed in a new spot until they have already become too abundant to eradicate,” she said. “Though 76 crabs at Dungeness Spit is more than we would ever like to see, the population hasn’t yet reached the numbers that are seen in areas of greatest infestation. And they are, as far as we know, still confined to a relatively small location….

“Preventing and managing biological invasions is similar to planning for a wild fire season: The best thing to do is prevent either invasions or wildfires from taking hold in the first place, but we know that some will occur despite our best efforts. It’s difficult to forecast exactly where, when or how severe they will be when they do pop up, and yet it’s imperative to respond quickly and aggressively as soon as they are detected.”

Emily added that we are fortunate in this area to have the tremendous support of volunteers, partners and beachgoers, all involved in the effort to prevent a permanent invasion of green crabs. Staff and volunteers at the Dungeness National Wildlife Refuge have been instrumental in placing and tending the traps placed in that area.

Amusing Monday: Human super powers and other oddball things

Humans have at least five super powers that few people know about, according to Mind Warehouse, a video producer with nearly 2 million subscribers on YouTube.

The one so-called “superpower” that intrigued me the most was the ability to distinguish warm water from cold water by sound alone. The super-powers video, found first on this page, challenges viewers to close their eyes and listen as someone pours two glasses of water — one hot and one cold.

According to the video segment, which begins at 2:34, between 80 and 90 percent of people who listen to the video can tell whether it is hot or cold water being poured into the glasses. It has something to do with bubbles, according to the video.

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Green crab invaders settle in on Dungeness Spit, Olympic Peninsula

An invasion of the European green crab, which started last summer in northern Puget Sound, appears to be continuing this spring with 16 green crabs caught in traps at one location on Dungeness Spit near Sequim.

European green crab
Photo: Gregory C. Jensen, UW

The new findings are not entirely unexpected, given that invasive green crabs have established a viable population in Sooke Inlet at the southern end of Vancouver Island in Canada. From there, young crab larvae can move with the currents until they settle and grow into adult crabs. Last summer and fall, green crabs were found on San Juan Island and in Padilla Bay.

The big concern now is that a growing population of invasive crabs could spread quickly to other parts of Puget Sound, causing damage to commercial shellfish beds and disrupting the Puget Sound ecosystem.

“It knocks the wind out of your sails for sure,” said Emily Grason when I asked how she felt about the latest discovery. “You feel kind of powerless, and you want to get out there and start doing things.”

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Hope is alive for restoration of Puget Sound shellfish beds

Officials in Washington state’s Shellfish Program have identified a clear pathway to meet a state goal of restoring 10,800 net acres of shellfish beds to a harvestable condition by 2020.

The 10,800-acre target, established by the Puget Sound Partnership, was considered overly ambitious by many people when the goal was approved in 2011. Many still believe that the shellfish restoration effort will go down in flames, along with other goals, such as increasing chinook salmon and killer whale populations by 2020.

In reporting on the Shellfish Implementation Strategy, a document still under development, I’ve learned that the goal is within reach if enough of the ongoing recovery efforts around Puget Sound continue to make progress. Please check out my latest stories “Bringing the shellfish back” and “Closing in on the magic number in Samish Bay,” both published in the Encyclopedia of Puget Sound.

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Crab Team training will foster the upcoming hunt for green crab invaders

A European green crab invasion may be taking place in Puget Sound, and Washington Sea Grant intends to enhance its Crab Team this summer with more volunteers looking in more places than ever before.

The second European green crab identified in Puget Sound was found in Padilla Bay, where three others were later trapped.
Photo: Padilla Bay Reserve

Training is about to get underway, and anyone with an interest in furthering science while being exposed to the wonders of nature may participate. It’s not always good weather, but I’ve been inspired by the camaraderie I’ve witnessed among dedicated volunteers.

The work involves going out to one or more selected sites each month from April into September with a team of two to four other volunteers. It is helpful to have folks who can carry the crab traps, plastic bins and other equipment. For details, check out the Washington Sea Grant website.

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Invasive oyster drills react differently to predators than natives

Invasive saltwater snails, including dreaded oyster drills, seem to be far more leery of predators than native snails under certain conditions, according to a new study by Emily Grason, whose research earned her a doctoral degree from the University of Washington.

An invasive Atlantic oyster drill feeds on a young Pacific oyster. // Photo: Emily Grason

Why non-native snails in Puget Sound would run and hide while native species stand their ground remains an open question, but the difference in behavior might provide an opportunity to better control the invasive species.

Of course, snails don’t actually run, but I was surprised to learn that they can move quite rapidly to find hiding places when they believe they are under attack.

Like many marine animals, snails use chemical clues to figure out what is happening in their environment. For her experiments, Emily created a flow-through system with two plastic shoeboxes. Chemical clues were provided in the upstream bin, while the reaction of the snails was observed in the downstream bin.

The most dramatic difference between native and non-native snails seemed to be when ground-up snails were deposited in the upstream bin, simulating a chemical release caused by a crab or other predator breaking open snail shells and consuming the tender morsels inside.

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More invasive crabs found; wider search will resume next spring

Padilla Bay, an extensive inlet east of Anacortes in North Puget Sound, could become known as an early stronghold of the invasive European Green crab, a species dreaded for the economic damage it has brought to other regions of the country.

Trapping sites for crabs (gray markers) during this week’s rapid assessment in Padilla Bay. The red markers show locations where invasive European green crabs were found.
Trapping sites for crabs (gray markers) during this week’s rapid assessment in Padilla Bay. Red markers show locations where three more invasive European green crabs were found.
Map: Washington Sea Grant

After one young green crab was found in Padilla Bay on Sept. 19 (Water Ways, Sept. 24), three more crabs were found during an extensive trapping effort this past week. All four crabs were captured at different locations in the bay. These four live crabs followed the finding of a single adult green crab in the San Juan Islands — the first-ever finding of green crabs anywhere in Puget Sound. (Water Ways, Sept. 15).

With these new findings in Padilla Bay, the goal of containing the crabs to one area has become a greater challenge. Emily Grason, who coordinates a volunteer crab-surveillance program for Washington Sea Grant, discusses the difficulty of putting out enough traps to cover the entire bay. Read her report on the fist day of trapping:

“Similar to our trip to San Juan Island, we are conducting extensive trapping in an effort to learn more about whether there are more green crabs in Padilla Bay. One difference, however, is scale. Padilla Bay is massive, and it’s hard to know exactly where to start. On San Juan Island, the muddy habitats where we thought crabs would do well are well-defined, and relatively limited. Padilla Bay, on the other hand, is one giant muddy habitat — well, not all of it, but certainly a huge portion. We could trap for weeks and still not cover all of the suitable habitat!”

In all, 192 traps were set up at 31 sites, covering about 20 miles of shoreline. The crab team was fortunate to work with the expert staff at the Padilla Bay National Estuarine Research Reserve, a group of folks who know the area well and had worked with shoreline owners to get approval for access.

Three of the four green crabs caught in Padilla Bay were young, probably washed into the bay during last winter’s warm currents, Emily said in her wrap-up report of the effort.

“All of the detections of European green crabs occurred on the east portion of the bay,” she wrote. “Though the sites varied somewhat in the type of habitat, all of the crabs were found relatively high on the shore, in high salt marsh pools, or within a few meters of the shore.

The first of four European green crabs found in Padilla Bay. Photo: Padilla Bay Reserve
The first of four European green crabs found in Padilla Bay.
Photo: Padilla Bay National Estuarine Reserve

“Padilla Bay has about 20 miles of shoreline, and, at last count in 2004, there were 143 acres of salt marsh habitat in the bay,” she continued.”These numbers suggest that there are a lot of places European green crabs could live in Padilla Bay, and protecting the bay from this global invader will undoubtedly require a cooperative effort.”

Yesterday, the response team held a conference call to discuss what to do next. Team members agreed that no more intensive trapping would take place this year, Sean McDonald of the University of Washington told me in an email.

Winter is a tough time to catch crabs. Low tides shift from daytime hours to nighttime hours, making trapping more difficult. Meanwhile, crabs tend to lose their appetite during winter months, so they are less likely to go into the traps to get food, experts say.

Researchers, shellfish growers and beach walkers are being asked to stay alert for the green crabs, not only in Padilla Bay but also in nearby Samish and Fidalgo bays.

The Legislature will need to provide funding to continue the citizen science volunteer monitoring program, which provided an early warning that green crabs had invaded Puget Sound. Whether the crabs will survive and in what numbers is something that demands more study and perhaps a major eradication effort.

Meanwhile, Washington Department of Fish and Wildlife would like to expand its overall Aquatic Invasive Species Program with additional efforts to prevent invaders from coming into Puget Sound. For information, check out my story on invasive species in the Encyclopedia of Puget Sound — specifically the section titled “Biofouling still mostly unregulated.”