Tag Archives: Crab

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: Giant crab has amazing grip, but species is at risk

Coconut crabs are giant land-based crustaceans that can grow to 3 feet wide, claw-to-claw. The crabs, frightening to some, inhabit islands in the Pacific and Indian oceans.

These crabs, which grow larger than any other land-based arthropod, are known for their uncanny strength. They get their name from an ability to break through coconut husks with their powerful claws. They can also break a lot of other things, as revealed in a variety of amusing videos, some of which I’ve posted on this page.

Coconut crabs became a topic of discussion among scientists last month when a group of Japanese researchers reported that they had measured the strength in the legs and claws of coconut crabs. They found that these crabs could lift four times their weight, and their pinching power was greater than that of any other kind of crab, even greater than the jaw strength of terrestrial predators. The report was published in the online journal Plos One.

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No new green crabs have been found, but the search will go on

No European green crabs were caught this week during an intensive two-day trapping program designed to see if any of the invasive crabs have gained a foothold in the San Juan Islands.

These are the locations and number of traps placed on Monday in the northern San Juan Islands. Map: Washington Sea Grant
These are the locations and number of traps placed in the northern San Juan Islands on Monday. // Map: Washington Sea Grant

If you recall, a single adult green crab was trapped Aug. 31 by a team of volunteers in the San Juan Islands. It was the first green crab ever found in Puget Sound, but experts have been worried about the crab for years. (See Water Ways, Sept. 3.) The volunteers are involved in a citizen science monitoring program to locate green crabs when they first arrive in Puget Sound and before they become a breeding population.

The response by professional leaders of the Crab Team was to place 97 traps in and around the location where the first crab was found. The effort was started on Monday and repeated on Tuesday. The maps on this page show the locations and the number of traps place at site on the two days. Hundreds of native crabs were trapped and inspected, but no green crabs were found.

These are the locations and number of traps placed in the northern San Juan Islands on Tuesday. Map: Washington Sea Grant
These are the locations and number of traps placed in the northern San Juan Islands on Tuesday. // Map: Washington Sea Grant

Although no live crabs were found, one molt (cast-off shell) from a green crab was found by Jeff Adams, a marine ecologist for Washington Sea Grant who manages the Crab Team of volunteers. The molt was close to where the live crab was found. The experts have not determined if the molt came from the first crab or if there might be other crabs in the area.

The next step is still being planned. It could involve another intensive trapping effort, perhaps in the spring, as well as increasing the number of volunteer trapping sites in the San Juan Islands. The volunteer program takes a hiatus in the winter, when the crabs are less active, but it will resume in the spring.

The next green crab training program is scheduled for March, when new and former citizen science volunteers will be taught how to identify green crabs and conduct an effective trapping effort in up to 30 locations throughout Puget Sound. To learn more about the volunteer program, check the Washington Sea Grant webpage “Get Involved” or sign up for a free email newsletter called “Crab Team News” (click “Newsletters”).

Emily Grason, Crab Team coordinator for Washington Sea Grant, was involved in the two-day intensive trapping program. Emily blogs about the effort on the Crab Team website:

You may want to review my recent writing project on invasive species for the Encyclopedia of Puget Sound, including a story about green crabs and the volunteer monitoring program.

Sean McDonald of Washington Sea Grant heads out to check on crab traps on Henry Island, not far from where the first green crab was found in Puget Sound. Photo: Emily Grason, WSG
Sean McDonald of Washington Sea Grant heads out to check on crab traps on Henry Island, not far from where the first green crab was found in Puget Sound. // Photo: Emily Grason, WSG

New publications provide fascinating info about local sea life

Those interested in the creatures that inhabit our local waterways may find themselves enthralled by two recent publications — one describing the many species of fish found in the Salish Sea and the other examining the lifestyles of crabs and shrimps living along the Pacific Coast.

The new fish report (PDF 9.2 mb), published by NOAA Fisheries, documents 253 species found in the Salish Sea, including 37 additional species not listed in the previous comprehensive fish catalog, now 35 years old.

Fourhorn poacher Illustration: Joe Tomelleri
Fourhorn poacher // Illustration: Joe Tomelleri

What caught my immediate attention in the report were the beautiful illustrations by Joe Tomelleri, who has spent the past 30 years capturing the fine features of fish from throughout the world. Check out the ornate fins on the fourhorn poacher and the muted colors of the spotted ratfish. I never realized that common ratfish wwere so beautiful.

The new report offers a preview of a much-anticipated book by Ted Pietsch, retired fish curator at the University of Washington’s Burke Museum, and Jay Orr, a biologist at NOAA’s Alaska Fisheries Science Center. The book, “Fishes of the Salish Sea,” will provide extensive descriptions as well as illustrations of all known species — including some early discoveries that came to light after publication of the new NOAA report. The book could be 600 pages or more.

Spotted ratfish Illustration: Joe Tomelleri
Spotted ratfish // Illustration: Joe Tomelleri

I interviewed author Ted Pietsch of Seattle and illustrator Joe Tomelleri of Leawood, Kans., for a piece incorporated into the Encyclopedia of Puget Sound.

The other book, “Crabs and Shrimps of the Pacific Coast” by Greg Jensen of Bremerton, pulls together information about 300 of these various crustaceans. The book, which has been on my review list for more than year, has won acclaim from experts in the field as well as casual observers of nature. The book comes with an associated computer disc of the book’s text, which allows one to link to other articles and reports. One can also load much of the book onto a smart phone, which can be taken to the shoreline and used as a field guide.

Book cover

“My goal was to make a book that would appeal to someone who just wants to learn about this stuff and would also be valuable to someone, like myself, who is a specialist in the field,” Greg told me.

I enjoy Greg’s light writing style, as he tells little stories in sidebars, shares brief biographies of key scientists and clears up myths and confusion. One sidebar, for example, tells us that the lines between shrimp and prawns have become blurred.

In Great Britain, he said, Crangonids, “with their stout, somewhat flattened form, were called ‘shrimp,’ while palaemonids were known as prawns.” In other places, prawns are considered larger than shrimp. Sometimes prawns refer to freshwater versus saltwater species.

Spot shrimp Photo: Greg Jensen
Spot shrimp // Photo: Greg Jensen

“Bottom line: There is no formal definition separating the two. Like the Queen’s English, once they left home for America and Australia, they became bastardized beyond recognition,” he wrote.

Greg, a scuba diver, shot about 90 percent of the pictures shown in the 240-page book. If nothing else, he told me, the book provided an excuse for him to dive in waters all along the coast.

“It was like a big scavenger hunt,” he said. “You look through the literature and you have this list (of crabs and shrimps). You dig up anything and everything about where to find them.”

Pacific rock crab Photo: Greg Jensen
Pacific rock crab // Photo: Greg Jensen

Like Ted Pietsch has done for fish, Greg has gone back to the original references about crabs and shrimp, taking pains to correct mistakes passed down through scientific literature. It has taken years to track down the many references to ensure accuracy and give credit to the right people, he said.

Greg, who grew up in Bremerton, was in grade school when a field trip took him to Agate Passage on a low tide, where he became intrigued by crabs. He soon started an extensive collection of dried crab shells. Looking back, Greg credits marine biology instructors Ted Berney at East High School and Don Seavy at Olympic College for helping him pursue his interests, eventually launching his career at the University of Washington.

Today, Greg still lives in Bremerton, researching, writing and teaching at the UW School of Aquatic and Fishery Science.

The book can be purchased directly from Greg Jensen, from Amazon and from Reef Environmental Education Foundation.

Amusing Monday: What stories crabs could tell

In recognition of what ought to be a great summer of crabbing on Puget Sound, I’ve compiled a variety of crab-related videos.

In the video player at right, you’ll learn about The Crabman, Brodie Anderson, a brave young man who communes with nature by catching crabs and talking to them.

Ever wonder how crabs act as they approach a crab pot sitting on the bottom of Puget Sound? What are they thinking as they partake of the goodies inside the trap? How do they feel when they realize they can’t get out? OK, maybe we won’t get answers to all these questions, but you can learn a lot from this time-lapse video (below) taken off Camano Island by Squire Productions. For more info on crabbing in Puget Sound, begin with the news release by the Washington Department of Fish and Wildlife.

In a series of rather odd videos, actor Patrick Duffy carries on discussions with a friend, who just happens to be a crab. My favorite is his conversation about “American Idol.” I always wondered if a singer prefers to be called “pitchy” if he or she is off-key or misses a few notes.

For more crab discussions, visit Patrick Duffy and the Crab. For the back-story on how these short features came about, check out Liz Shannon Miller’s blog entry “Patrick Duffy and the crab make for a very odd couple.”

I’m not sure how I missed the 1957 movie “Attack of the Crab Monsters,” but it is a classic, if the movie trailer is any indication:

“Here are monsters with razor sharp claws that hand grenades and dynamite cannot stop, nor searing fire and flame, nor tons of crushing rocks, as mankind faces its last desperate chance.”

Another classic battle is the crab versus the millipede, a battle that seemingly never ends.

There is no entanglement at all in this skirmish between a crab and a Dachshund puppy.

Crabs are famous for their mass movements of molting and mating, as shown in these videos from Australia and Cuba. All this should give you something to think about when you’re pulling in that crab pot.