Tag Archives: European green crab

Green crabs go wild near Sequim, but experts say control is still possible

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.

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.

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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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.”

Second invasive green crab discovered in northern Puget Sound

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 Reserve
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 second green crab was found by Glen Alexander of the Padilla Bay National Estuarine Research Reserve while overturning rocks with a group of students.

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:

  1. Learn how to how to identify green crab. Check out the Crab Team webpage at wsg.washington.edu/crabteam or Facebook and Twitter @WAGreenCrab.
  2. Take a photo and report sightings to the WSG Crab team at crabteam@uw.edu.
  3. Shellfish collected in one location should never be released or “wet stored” in another location unless authorized by WDFW.
  4. Clean, drain and dry recreational gear or other materials after beach visits.

If you haven’t seen it, you may want to review a series I wrote on invasive species for the Encyclopedia of Puget Sound, including a story about green crabs and the volunteer monitoring program.

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

A single green crab invader has been found, the first in Puget Sound

A European green crab, one of the most dreaded invasive species in the world, has finally arrived in Puget Sound.

Caught in a crab trap on San Juan Island were these animals — including the first European green crab ever found in Puget Sound. Photo: Photo Craig Staude, courtesy of Washington Sea Grant
Caught in a crab trap on San Juan Island were these fish, along with the first European green crab ever found in Puget Sound.
Photo: Craig Staude, courtesy of Washington Sea Grant

A single adult green crab was caught in a trap deployed on San Juan Island by a team of volunteers involved in a regionwide effort to locate the invasive crabs before they become an established population.

Until now, green crabs have never been found in Puget Sound, although they have managed to establish breeding populations along the West Coast — including Willapa Bay and Grays Harbor in Washington and the western side of Vancouver Island in British Columbia.

Coincidentally, I recently completed a writing project on invasive species for the Encyclopedia of Puget Sound, including a story about green crabs and the volunteer monitoring program.

Here’s what I wrote: “Puget Sound has so far avoided an invasion of European green crabs — at least none have been found — but the threat could be just around the corner….

“Green crabs are but one of the invasive species threatening Washington state, but they are getting special attention because of fears they could seriously affect the economy and ecosystem of Puget Sound. Besides devouring young native crabs and shellfish, they compete for food with a variety of species, including fish and birds.”

Along the beach, careful observers can often find crab molts. The green crab, upper left, can be distinguished by the points on its carapace. Photo: Jeff Adams, Washington Sea Grant
Along the beach, careful observers may find weathered crab molts of all sizes. The green crab, upper left, can be distinguished by the five points on each side of the carapace. (Click to enlarge.)
Photo: Jeff Adams, Washington Sea Grant

In Canada, one breeding population has been identified in Sooke Inlet near the southernmost tip of Vancouver Island. That’s about 40 miles away from Westcott Bay, where Puget Sound’s first green crab was found on Tuesday.

It is likely that the crab traveled to San Juan Island in its early free-swimming larval form by drifting with the currents, said Jeff Adams, a marine ecologist for Washington Sea Grant who manages the Crab Team of volunteers. This crab likely settled down in suitable habitat and located enough food to grow into an adult. Based on the crab’s size, it probably arrived last year, Jeff told me.

European green crab Photo: Gregory C. Jensen, UW
European green crab // Photo: Gregory Jensen, UW

Finding a green crab in Puget Sound is alarming, Jeff said, but it is a good sign that the first crab was found by the volunteer monitors. That suggests that the trapping program is working. If this first crab turns out to be a single individual without a mate, then the threat would die out, at least for now.

The concern is that if one crab can survive in Puget Sound, then others may also be lurking around, increasing the chance of male-female pairing. The next step is to conduct a more extensive trapping effort in the area where the first green crab was found, then branch out to other suitable habitats in the San Juan Islands, Jeff said. The expanded effort is planned for the week of Sept. 11 and will include a search for molts — the shells left behind when crabs outgrow their exoskeletons and enter a new stage of growth.

Green crab
Green crab

Researchers and others who work with invasive species quickly recovered from their initial surprise at finding a green crab in Puget Sound, then got down to business in planning how to survey for crabs and manage their potential impacts.

Allen Pleus, coordinator of the Aquatic Invasive Species Program at the Washington Department of Fish and Wildlife, told me several weeks ago that if green crabs show up in Puget Sound, one idea would be to conduct an extensive trapping program to eradicate or at least reduce their population. First, however, the extent of the infestation must be identified. I expect that more extensive trapping will be planned next spring and summer to look for offspring from any successful mating in the San Juan Islands.

This video shows a green crab found in Willapa Bay on the Washington Coast.

Typically, green crabs are found in marshy areas, which are habitats extensively used by our native hairy shore crab. But Jeff tells me that some populations of green crabs seem to be expanding their habitat into more exposed rocky areas.

With roughly 400 suitable sites for the crabs in Puget Sound, invasive species experts are calling for everyone who visits a beach to look for green crabs and their molts. One can learn to identify green crabs from the Washington Sea Grant website. The volunteer trapping program is funded by the Environmental Protection Agency with a grant to Fish and Wildlife.

A public discussion about green crabs and how people can help protect Puget Sound from an invasion is scheduled for Sept. 13 at Friday Harbor Laboratories on San Juan Island. See Crab Team Public Presentation.

Invasive species hitching a ride into Puget Sound

We hear about the “balance of nature,” but it’s not something that we can truly understand until the balance is thrown out of whack by something like climate change or invasive species.

Until I began a recent reporting project for Puget Sound Institute, I never realized that San Francisco Bay was such a hotbed of invasive species. Beginning with the California Gold Rush, ships began moving in and out of the bay in unbelievable numbers, arriving from ports all around the world. Now, more than 200 non-native species are making their permanent home in the bay — including some species that have thoroughly altered the local ecosystem.

So far, we have been lucky in Puget Sound. Experts say we have about 75 firmly established non-native species, yet none of them have created the widespread damage caused in San Francisco Bay by European green crabs and Asian clams or in the Great Lakes by zebra mussels. The video on this page does a good job of telling the Great Lakes story, which has been repeated all over the world.

Once people in Washington state realized how disruptive invasive species can be, the struggle was on to protect Puget Sound from alien invaders — particularly those found in San Francisco Bay, which is just a short hop away on the world scale. My series of stories talks about concerns for Puget Sound and the efforts to control a possible invasion.

Three weeks ago in Water Ways, I described legislation that would reduce state and federal controls over invasive species. See “Bill could increase risks of alien species invasions in Puget Sound waters.”

On the East Coast, where they are native, striped bass are one of the most popular sport fish. Here, Angela Anning of Connecticut shows off her impressive striper. On the West Coast, striped bass could be considered an invasive species. Photo: NOAA
On the East Coast, where they are native, striped bass are one of the most popular sport fish. Here, Angela Anning of Connecticut shows off her impressive striper. On the West Coast, striped bass could be considered an invasive species.
Photo: NOAA

Invasive species range in size from microscopic viruses to four-foot-long striped bass. In California, the striped bass became a prized sport fish after it was intentionally introduced in 1879. But over the past decade concerns have grown for their effects on the salmon population. The jury is still out on whether high numbers of stripers should be sustained for anglers or the population should be fished down rapidly to save salmon and other species. Check out these stories:

Meanwhile, striped bass have been moving up the West Coast, possibly because of warmer waters due to climate change. A few years ago, a 55-pounder was caught in the Columbia River, and I’ve heard rumors that they have been seen in the Strait of Juan de Fuca.

On the small side, I report on a tiny crustacean, an invasive copepod that has almost entirely displaced native copepods in Samish Bay in northern Puget Sound. Copepods are important prey for small fish, including herring, which feed the larger salmon. The invasive copepods are smaller and more difficult for fish to see, which could have a cascading effect on the entire food web.

Invasive copepod Oithona davisae under magnification Photo: Jeff Cordell, University of Washington
Invasive copepod Oithona davisae
Photo: Jeff Cordell, UW

A major concern for Puget Sound biologists is the European green crab, which could move into Puget Sound from San Francisco Bay in ballast water or with warm ocean currents during an El Niño year, like the one just past. As I describe in the new series, a major program involving citizen science volunteers is ongoing in a search to find the first green crabs before they gain a foothold.

Pacific oysters, another non-native species, were intentionally brought to the Northwest from Japan in the early 1900s to replace the native Olympia oyster, which had been decimated by poor water quality. Pacific oysters soon became a mainstay of the shellfish industry in the Puget Sound region and are now growing thick in numerous areas.

European green crab Photo: Washington Sea Grant
European green crab
Photo: Gregory C. Jensen, UW

Similar introductions of Pacific oysters occurred in California beginning more than 100 years ago, but for some reason the oyster populations never took hold, according to a report in the publication California Fish and Game (PDF 1.7 mb). Finally, in the early 2000s, the invasion began to take off.

“It remains unclear why there should be a successful invasion now, given the failure of previous attempts to deliberately introduce the species both locally and throughout California…,” the report says.

“If populations in Southern California waters do continue to expand and grow, as they have in other areas where they have invaded, it will undoubtedly bring changes to the way our estuarine intertidal habitats function as well as in the way we must manage them.

Pacific oyster Photo: Washington Sea Grant
Pacific oyster
Photo: Washington Sea Grant

“Because Pacific oysters rapidly reach large sizes, they could pose problems related to fouling of maritime equipment, infrastructure, and vessels,” the report continues. “Pacific oysters stand out as one of the most transformative invaders of marine ecosystems.”

As Washington state takes steps to keep alien species from invading Puget Sound from California, California officials may adopt similar measures to block invaders from coming into that state.

Please take a look at this package of stories I wrote for Puget Sound Institute, with editing by Jeff Rice and design by Kris Symer: