I heard some legitimate questions about how to identify European
green crabs and what to do if you find one. The main thing is to
get a photograph and send it to the Washington Sea Grant Crab Team,
which is leading the war on green crabs. I’m reminded that it is
illegal to possess a green crab without a permit.
Here are some links from the Crab Team website that could be
helpful:
I’m also pleased to see the announcement of a free online
webinar on July 10 to help people identify European green crabs.
The two-hour “First Detector
Training Webinar” is co-sponsored by the Crab Team and
Washington Invasive Species Council. Register ahead of time to get
information about the event.
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.
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.
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 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
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:
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
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
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
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.
“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
“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
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.
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.
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.”
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.
