The ongoing story of the European green crab invasion offers us
scientific, social and even psychological drama, which I would like
to update by mentioning four new developments:
The somewhat mysterious finding of a partially eaten green crab
on the Bellingham waterfront,
A “story map” that spells out much of what we know about
European green crabs in Puget Sound, including maps, photos and
videos.
Information about Harper Estuary in South Kitsap and other
areas where groups of citizen scientists are on the lookout for
green crabs, and
Reports of a new breed of European green crab in Maine that
attacks people and may prove to be more destructive than the green
crabs that have lived in the area for a very long time.
The war against the invasive European green crab continues in
Puget Sound, as this year’s Legislature offers financial support,
while the Puget Sound Crab Team responds to crabs being caught for
the first time in Samish Bay in North Puget Sound and at Kala Point
near Port Townsend.
In other parts of the country where green crabs have become
established, the invaders have destroyed native shoreline habitat,
diminished native species and cost shellfish growers millions of
dollars in damages. See
Environmental Protection Agency report (PDF 1.3 mb).
European green crab trapping
sites in Puget Sound.
Map: Washington Sea Grant
In Puget Sound, it’s hard to know whether the crabs are being
trapped and removed rapidly enough to defeat the invasion, but so
far humans seem to be holding their own, according to Emily Grason,
who manages the Crab Team volunteer trapping effort for Washington
Sea Grant.
“The numbers are still in line with what we saw the past two
years,” Emily told me. “Since the numbers have not exploded, to me
that is quite a victory. In other parts of the world, they have
been known to increase exponentially.”
The largely volunteer Crab Team program is focused on placing
baited traps at 56 sites in Puget Sound, as shown in the first map
on this page. About 220 trained volunteers are involved in that
work, with various federal, state and tribal agencies adding about
40 additional people.
An app used for reporting King Tides can also be used to report
marine debris along the shoreline. Check out the
news release issued today by the Washington Department of
Natural Resources.
—–
Higher-than-predicted marine waters, brought about in part by
recent weather conditions, have given us unexpected “King Tides” in
many areas of Puget Sound.
I noticed that the waters of Hood Canal seemed exceedingly high
this afternoon, as I drove along Seabeck Highway where the road
hugs the shoreline. The waters were not supposed to be this high,
according to tide tables developed by the National Oceanic and
Atmospheric Administration, so I checked some actual levels
recorded at nearby locations.
High-water levels measured on the waterfronts in Seattle, Tacoma
and Port Townsend were nearly 1½ feet higher than what had been
predicted by NOAA for those areas. For example, in Seattle the
preliminary high-water level was listed at a tidal elevation of
12.98 feet at 12:54 p.m. today, compared to a predicted high tide
of 11.56 feet.
This is the season for King Tides, a name given to the highest
tides of the year. High tides, mostly generated by the alignment of
the sun and the moon, are predicted for Christmas Eve, rising
higher to the day after Christmas and then declining. But, as we’ve
seen this week, as well as on Thanksgiving Day, predicted high
tides can be dramatically boosted by heavy rains, low atmospheric
pressure and onshore winds.
As one can see by looking at observed
and predicted tidal levels in Seattle, the actual tidal level
has exceeded the predicted level more often than not over the past
30 days — and lately it has been higher by quite a lot (shown in
chart at bottom of this page). Actual levels are measured in real
time in only 14 places in Washington state. One can access the
charts from NOAA’s
Water Levels — Stations Selections page.
King Tides are promoted as an event by Washington Sea Grant and
the Washington Department of Ecology, because today’s extreme tides
provide a reference point for sea-level rise caused by climate
change. The highest tides of today will be seen more often in the
future, and even higher tides are coming. Check out the blog post
on
Water Ways from Jan. 3 of this year. See also the website
“Washington King Tides Program.”
Washington Sea Grant has posted a list of dates when high tides
are expected in various areas, called
King Tides Calendar. Sharing photos of high tides hitting the
shoreline is part of the adventure, so sign up for MyCoast to share your pictures or view
images posted by others, or download the cellphone app to make the
connection even easier.
The chart shows the actual
tidal water levels in Seattle (red) compared to the predicted
levels (blue). Click to go to NOAA’s website.
Chart: NOAA
Dungeness Spit on the Strait of Juan de Fuca near Sequim remains
a hot spot for the invasive European green crab, which first showed
up in Puget Sound during the fall of 2016.
This small male crab is one of
the European green crabs caught last year in traps at Dungeness
Spit.
Photo: Allen Pleus
The green crab, one of the most dreaded invasive species in the
world, brings with it the potential to destroy shellfish beds and
disrupt key habitats essential to native species in Puget
Sound.
Thankfully, except for the Dungeness Spit, new findings of green
crabs have been almost zero since a massive volunteer trapping
effort resumed in April throughout most of Puget Sound.
I do have some additional news about green crabs to share, so
please read on for a discussion of these topics:
Witnessing Puget Sound’s “king tides” could return as a more
popular outdoor activity this year, as Washington Sea Grant takes
the lead in promoting the event.
Locations where people have
posted king tide photos on the Witness King Tides
website
“King tides,” which are recognized in coastal areas across the
country, is the name given to the highest tides of the year. These
are times when people can observe what average tides might look
like in the future, as sea levels continue to rise.
The highest tide of 2018 is forecast for this Friday around 8
a.m., although the exact time depends on the location in Puget
Sound.
Activities include taking pictures of shoreline structures
during these high-tide events and then sharing the photos with
others. One can try to imagine what the landscape would look like
in a given location if the water was a foot or more higher. King
tide activities can be fun while adding a dose of reality to the
uncertainty of climate change.
King tides by themselves have nothing to do with climate change,
but these extremes will be seen more often in the future as new
extremes are reached. As things are going now, experts say there is
a 50 percent chance that sea levels in Puget Sound will rise by at
least 7 inches in the next 22 years and keep going from there. They
say there is a 99 percent chance that sea levels will be at least
2.4 inches higher by then. Check out the story I wrote in October
for the Encyclopedia
of Puget Sound.
Washington Department of Ecology, which had been promoting king
tides each year, has backed away from the event in recent years. In
the beginning, I thought the idea of king tides seemed kind of
silly, because high tides are affected by weather conditions on a
given day. But I came to embrace the idea that watching these
high-tide events will help shoreline residents and others
understand the challenges we are facing in the Puget Sound
region.
Addressing sea level rise may not be easy, but some waterfront
property owners are beginning to face the problem, as I described
in another story in the Encyclopedia of
Puget Sound.
During a king tide event in December 2012, the Kitsap Sun and
other newspapers covered the resulting flooding by running
photographs of high water in many places throughout Puget Sound. A
low-pressure weather system that year made extreme high tides even
more extreme. In fact, officials reported that the high tide came
within 0.01 feet of breaking the all-time tidal record set for
Seattle on Jan. 27, 1983. See
Water Ways, Dec. 18, 2012.
Washington Sea Grant, associated with the University of
Washington, has now taken over promotion of king tides, and we
should soon see an improved website, according to Bridget Trosin,
coastal policy specialist for Sea Grant. Bridget told me that she
hopes to promote more local events, such as getting people together
to share information during extreme high tides.
Sea Grant is sponsoring a King Tide Viewing Party this Friday at
Washington Park boat launch in Anacortes, where Bridget will spell
out what high tides may look like in the future. Warming
refreshments will be provided, according to a
news release about the event.
Wherever you live around Puget Sound, you can go down to the
water to document the high tide, perhaps starting a new photo
gallery to show how high tides change at one location during king
tides in the future, as some folks are doing in Port Townsend.
For tips on preparing and posting photos, visit the “Witness
King Tides — Washington State” website, then check out the page
“Share
Your Photos.” To see the locations where photographs have been
taken, go to the
map page. One can click on locations on the map to see the
photographs taken from that spot.
King tides occur when the moon and sun are on the same side of
the Earth at a time when the moon comes closest to the Earth. Their
combined pull of gravity raises the sea level. The presence of a
low-pressure system can raise the tides even higher than
predictions published by the
National Oceanic and Atmospheric Administration.
Friday’s high tide is predicted to be 13.2 feet in Seattle at
7:55 a.m. We won’t have a tide that high again until January of
2019, according to NOAA. Still, Feb. 2 will see a 13.1-foot tide in
Seattle, and tides exceeding 12 feet are predicted for June 16,
Nov. 27, Dec. 1, Dec. 10, and daily high tides from Dec. 26 through
the end of this year.
Nearly 100 invasive European green crabs were trapped along
Dungeness Spit near Sequim this past spring and summer — far more
than anywhere else in Puget Sound since the dangerous invaders
first showed up last year.
European green crabs started
showing up in traps on Dungeness Spit in April.
Photo: Allen Pleus, WDFW
Despite the large number of crabs found in this one location,
green crab experts remain undeterred in their effort to trap as
many of the crabs as they can. And they still believe it is
possible to keep the invasion under control.
“In a lot of ways, this program is functioning much as we had
hoped,” said Emily Grason of Washington Sea Grant, who is
coordinating volunteers who placed hundreds of traps in more than
50 locations throughout Puget Sound. “We look in places where we
think the crabs are most detectable and try to keep the populations
from getting too large, so that they are still possible to
control.”
After the first green crabs were found on Dungeness Spit in
April, the numbers appeared to be tapering off by June, as I
described using a graph in
Water Ways on June 24. The numbers stayed relatively low, with
three caught in July, two in August, three in September and two in
October. But they never stopped coming.
The total so far at Dungeness Spit is 96 crabs, and more can be
expected when trapping resumes next spring. The good news is that
all the crabs caught so far appear to be just one or two years old
— suggesting that they likely arrived as free-floating larvae. That
doesn’t mean the crabs aren’t mating at Dungeness Spit, but the
trapping effort has reduced the population to the point that males
and females are probably having a tough time finding each
other.
Officials with the U.S. Fish and Wildlife Service, which has
taken charge of trapping at Dungeness Spit, will need to decide
whether to attempt a complete eradication of the local green crab
population, according to Allen Pleus, coordinator of Washington
State’s Aquatic Invasive Species Program. That would involve
managing a large number of traps until no more crabs are seen. The
alternative, he said, would be to manage the crab population with
fewer traps and make further decisions down the line.
During one three-day stretch last year, 126 traps were deployed
in areas on and near Dungeness Spit, part of the Dungeness National
Wildlife Refuge managed by the Fish and Wildlife Service.
Even with the most exhaustive trapping program, there is no
guarantee that green crabs won’t be found again, Allen said. The
likely source of the crab larvae is an established population of
green crabs in Sooke Inlet on Vancouver Island, just across the
Strait of Juan de Fuca from Dungeness Spit.
Allen said he is disappointed that crabs continued to be caught
on or near Dungeness Spit — mainly in one small area near the
connected Graveyard Spit. “But I am very impressed with the
dedication of the U.S. Fish and Wildlife Service, which continued
to trap throughout the summer,” he said.
While there is no evidence so far that the invading crabs have
reproduced at Dungeness Spit, it is possible that mating took
place. If so, everyone involved in the green crab effort could face
a whole new group of young crabs next year.
I have to admit that I was worried last spring that funding for
the essential volunteer effort would run out as officials scrambled
to finance the start of trapping season. But the Environmental
Protection Agency agreed to fund the project through next year
under the Marine and Nearshore Grant Program.
Meanwhile, Allen said he is working with Canadian officials to
see what can be done about reducing the population of green crabs
in Sooke Inlet, which is likely to remain a source of the invasive
crabs coming into Washington state. The Canadians have their own
concerns about green crabs, which can severely damage commercial
shellfish operations and disrupt critical eelgrass habitats.
“Sooke Inlet is the only known population established in the
Salish Sea,” Allen said. “We are working with Canada and setting up
meetings this winter to continue our discussions.”
Canadian officials are monitoring for green crabs on their side
of the border, but the effort is much less than in Puget Sound. It
appears that only limited efforts have been made so far to control
the Sooke Inlet population and reduce the amount of invasive crab
larvae heading to other areas in the Salish Sea.
Researchers are still investigating the conditions that allow
green crab larvae to survive long enough to grow into adult crabs.
It appears that larvae move up the coast from California during
warm years and particularly during El Niño periods, Emily told me.
That may explain why the Puget Sound traps began catching so many
crabs the past two summers.
“The signal we are seeing does point to 2015 and ‘16 as being
the first arrivals,” she said. “Our working hypothesis is that warm
years are spreading larvae.”
That could offer renewed hope for the immediate future, since El
Niño is over and we may be going into cooler La Niña conditions
next year.
No new crabs have shown up in the San Juan Islands, where Puget
Sound’s first green crab was discovered last year. But two more
were found about 30 miles away in Padilla Bay, where four crabs
were caught last fall.
New areas with green crabs this year are Lagoon Point on Whidbey
Island, where two crabs were caught, and Sequim Bay, not far from
Dungeness Spit, where one crab was caught.
The latest concern over green crabs is Makah Bay on the outer
coast of Washington near the northwest tip of the Olympic
Peninsula. In August, a beach walker spotted a single green crab on
the Makah Tribe’s reservation and sent a picture to the Puget Sound
Crab Team, which confirmed the finding. Tribal officials launched a
three-day trapping effort last month and caught 34 crabs — 22 males
and 12 females — in 79 traps.
An aggressive trapping effort is being planned by tribal
officials for the coming spring. Interested volunteers should
contact Adrianne Akmajian, marine ecologist for the Makah Tribe, at
marine.ecologist@makah.com
The Makah effort is separate from the Puget Sound Crab Team,
which encourages beach goers to learn to identify green crabs by
looking at photos on its website. Anyone who
believes he or she has found a green crab should leave it in place
but send photographs to the crab team at crabteam@uw.edu
Emily said she is most proud of all the people and organizations
that have come together as partners to quickly locate the invasive
crabs and advance the science around the issue. Such cooperation,
she said, makes the impact of the program much greater than it
would be otherwise.
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.”
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.
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. 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 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.”
A second European green crab has been found in Puget Sound, this
one in Padilla Bay — about 30 miles southeast of where the first
one was discovered about three weeks ago.
A second European green crab
has been found in Puget Sound, this one in Padilla Bay.
Photo: Padilla Bay National Estuarine Research
Reserve
Green crabs are an invasive species known to devour a variety of
native species and alter habitats where they have become
established. Keeping green crabs out of Puget Sound has been a goal
of state officials for years.
After the first green crab was caught in a volunteer trapping
program three weeks ago, experts mounted an intensive trapping
effort to see if other green crabs were in the area around Westcott
Bay in the San Juan Islands. (Water
Ways, Sept. 3). No live crabs were found, but one cast-off
shell (molt) was discovered nearby (Water
Ways, Sept. 15).
The latest find is a young female crab, 34 millimeters across,
which may have grown from a larva dispersed last winter.
“We were relieved to find very little evidence of a larger
population of invasive European green crab in Westcott Bay,” Emily
Grason of Washington Sea Grant said in a
news release (PDF 371 kb). “But finding an additional crab at a
site more than 30 miles away suggests that ongoing vigilance is
critical across all Puget Sound shorelines. WSG’s Crab Team is
committed to continuing the efforts of volunteer monitoring as
resources allow, but we also rely on beachgoers to keep a watchful
eye out for this invasive species.”
A second rapid-response effort will get underway Monday with
more traps being deployed over a larger area than last time. The
goal is to locate any crabs that may have made a home in the area
and determine where the crabs might be gaining a foothold.
The advice for beachgoers remains the same:
Learn how to how to identify green crab. Check out the
Crab Team webpage at wsg.washington.edu/crabteam or Facebook and
Twitter
@WAGreenCrab.
Take a photo and report sightings to the WSG Crab team at
crabteam@uw.edu.
Shellfish collected in one location should never be released or
“wet stored” in another location unless authorized by WDFW.
Clean, drain and dry recreational gear or other materials after
beach visits.
