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Can biologists estimate the massive loss of shellfish caused by low tides, high temps?

The putrid smell of rotting shellfish on some beaches in Puget Sound and elsewhere along the West Coast were a clear sign that large numbers of clams, mussels, oysters and other intertidal creatures were killed from exposure to extreme low tides, record-breaking temperatures and a blazing hot sun.
The total losses of shellfish that perished late last month may be difficult to estimate, but experts are beginning to piece together evidence from shoreline residents, state and tribal biologists, and commercial shellfish growers. Their goal is to describe what took place during the record-breaking temperatures of June 25-29 during some of the lowest tides of the past century.

The recent heatwave killed large numbers of shellfish throughout Puget Sound, including these butter clams in Quartermaster Harbor, Vashon Island. // Photo: Ron Carr

Understanding what happened during that June event might help avoid future shellfish disasters as the climate continues to change with no end in sight, officials say.
“We’ve been getting reports from Puget Sound to Canada, including the outer coast,” said Teri King, a shellfish biologist with Washington Sea Grant. “The effects of the heatwave were not uniform. Some areas got hammered and some seemed to escape (the problems).”
Tori Dulemba, who lives on the North Shore of Hood Canal near Tahuya, owns a south-facing beach with a gradual slope. Those conditions led to a long period of exposure to the hot sun when afternoon tides were the lowest since 2008 and when temperatures soared well above 100 degrees.
“You could easily smell the rotting shellfish,” Tori told me. “We knew immediately what it was. The oysters were cooked. The mussels were still attached, but the shells were empty. It was heart-breaking.”
The odor, she said, was much like the smell of dead salmon in areas where large numbers of fish still return to spawn and die in the streams. After a few days, the smell of dead shellfish dissipated, and it was gone after a week or so, but empty shells remained.
Teri King, who coordinates the Bivalves for Clean Water citizen education and monitoring program, said the first reports she received included descriptions of stressed clams digging themselves out of the ground and opening up on the surface of various beaches.
Based on reports, it seems that sand dollars were the first to succumb, followed by cockles, varnish clams, mussels, littleneck clams and butter clams, she said. There were also reports of dead Olympia oysters and Pacific oysters. Even barnacles turned up dead, while some sea stars and anemones also were killed.
A large number of the big moon snails common to Puget Sound got so hot that they literally uncurled themselves and came out of their shells, lying like balls on the beach, Teri said.
During the recent heatwave, tide levels were among the lowest in the past century. At Union on Hood Canal, shown here, the level was estimated to be at -4.37 feet at noon on June 25. Click to visit NOAA’s website for more specific data. // NOAA Tide Predictions

It seems that some areas were more sheltered from the sun or less affected by low tides because of the slopes of the beaches or the direction they faced. In general, problems were worse in South Puget Sound than in the north, Teri said, probably because the tides are more pronounced the farther south you go, leaving shellfish exposed for longer periods of time.
Teri and other officials are still taking observations and photographs from shoreline observers who were able to note the effects on shellfish caused by the extreme and extended heat. The Washington Department of Fish and Wildlife has provided an online form for observers to fill out, or they can send their information by Email.
Camille Speck, intertidal shellfish manager for WDFW, confirms the hit-and-miss nature of the massive shellfish die-off. While some public beaches were affected, others seem to have gotten by with minimal effects.
“What we saw at Dosewallips was very heartening,” Camille told me. “One-year-old or two-year-old oysters seemed to be doing just fine.”
She was speaking of Dosewallips State Park, a popular beach open to the public for shellfish harvesting. The beach lies on the western shoreline of Hood Canal, which may be better sheltered from the heatwave than the eastern shore or the northern shore around the “bend”.
Camille has yet to survey a number of public beaches, so she can’t say whether recreational shellfish seasons might need to be shortened to ensure future production. In some cases, quotas may be adjusted next year to compensate for losses, depending on the number of recreational harvesters and the amount of shellfish taken the rest of this year.
Photo: Ron Carr, Quartermaster Harbor

It was like a “perfect storm,” having such extreme low tides occurring coincidentally during the record-breaking heat, Camille said. Only two tidal periods in the last 100 years — one in 2008 and the other in 1916 — were lower, she said, and the temperatures climbed to levels never seen before in many places.
In Seattle, for example, the city had experienced 100-degree temperatures only three times in the past 126 years before they reached that level three days in a row, breaking the all-time record with 104 degrees on June 27 and again the next day with 108 degrees.
Meanwhile, some commercial shellfish growers have been gathering information to record their losses and possibly receive disaster relief from the federal government. Recent revisions to a federal program called Emergency Assistance for Livestock, Honey Bees and Farm-raised Fish (ELAP) may provide compensation for growers who can document their losses to the U.S. Department of Agriculture, officials say. For information, contact your county office of the Farm Service Agency.
A major hurdle in coming up with an estimate of actual losses — for commercial or noncommercial shellfish beds — is knowing what shellfish were present before the heatwave killed a portion of the shellfish.
Margaret Pilaro, executive director of Pacific Coast Shellfish Growers Association, said it is her understanding that growers must notify the USDA of potential losses within 30 days of the event. She has been trying to notify all of Washington’s certified shellfish growers of the possibility for financial aid to make sure that they don’t miss the deadline.
Tribal biologists also are out surveying the shellfish die-off, especially in areas where tribes have plans to harvest shellfish, as allowed by treaty. For state and private lands not cultivated for shellfish, the tribes are entitled to half the harvestable amount.
Biologists hope that a rough estimate of the total damage caused by the heat and low tides can be achievable, although such an estimate will be complicated by the patchy nature of the losses as well as the uncertainty about what was present in some areas before the event. For now, the main focus is to gather information from as many beaches as possible throughout Puget Sound.

In the topsy turvy world of climate change, Western Canada to the north experienced a similar but even more punishing heatwave, according to Tom Di Liberto, a meteorologist with CollabraLink Technologies. He says Lytton, British Columbia, reached 116 degrees on June 27, breaking the all-time record for all of Canada. But the oppressive weather was not over, as the temperature rose to 118 degrees the next day and then to 121 degrees on June 29. That is hotter than the desert town of Las Vegas, Nev., has experienced since records were first kept, according to Tom.
Likewise, the shellfish in British Columbia were reported to be cooking on the beach, perhaps even worse than in Puget Sound, as reported by Canadian news outlets.
Chris Harley, a marine biologist at the University of British Columbia, threw out an estimate of a billion shoreline creatures perishing in the Salish Sea as a result of the heat. That number, reported by Alex Migdal of CBC News, was crudely calculated by expanding the findings from a small area. The number subsequently raised a lot of eyebrows among experts on both sides of the border — but who could dispute it?
Commenting on the estimate, Chris Neufeld of Bamfield Marine Sciences Centre on Vancouver Island, said he was not surprised, adding, “It was very disheartening to realize we’re actually in this moment that we’ve been predicting for a long time.”

As in a pandemic, the battle against invasive species may well depend on early actions

As Americans, we have become all too familiar with the spread of a deadly virus and the terrible consequences of a delayed response to an outbreak. As a result of our experience, I’m wondering if some of us might have a more visceral sense about the need to control invasive species.
I’m not saying that the ecological, economic and cultural disturbances wrought by invasive species are on par with a massive loss of human life. But the common denominator is a biological perturbation that occurs suddenly and threatens to expand rapidly out of control, leaving permanent damage. The ultimate outcome depends on reaction to the threat.
“In the invasion world, early detection and rapid response is the best way to manage invasive populations,” said Emily Grason, a marine ecologist with Washington Sea Grant. “That’s similar to a pandemic. You want to find outbreaks when they are small and then react very quickly.”

Trapping and detection sites along Washington’s inland shorelines in 2020. (Click to enlarge.) The filled yellow circles show where European green crabs were captured in 2020, with the size of circle representing average capture rate. The open yellow circles show where green crabs were trapped in previous years but not in 2020. Open black circles are sites where no crabs have ever been caught. Graphic: Washington Sea Grant

Emily manages Sea Grant’s Crab Team, a group of more than 200 volunteers and professionals who systematically set crab traps in bays and estuaries to locate early infestations of the European green crab. This small crab, considered one of the world’s most damaging invasive species, has taken over bays on the East Coast, disrupting natural conditions. When a green crab is caught in Puget Sound, the first effort is to rapidly deploy many more traps to assess and reduce the crab population before it grows out of control.
Emily describes several ways that reactions to an invasion of nonnative species may resemble a pandemic — such as communicating the risks to the public and political leaders, determining priorities for action with limited resources, and enlisting the help of enough people to stay ahead of the threats.
“We don’t want to be flippant about this comparison,” Emily told me. “Human lives are at stake in a pandemic, and there are real differences in the immediate and long-term consequences.”
While not a direct threat to human health, European green crabs could take a heavy toll on native shellfish, destroy eelgrass beds important to salmon and forage fish, and consume commercial clams and oysters with financial losses to the shellfish industry. The Legislature has awakened to the threat with increased funding in recent years, as lawmakers also invest in battles against other invaders — from zebra mussels that could clog up critical water pipelines to Asian giant hornets that threaten to wipe out honey bee colonies.
Meanwhile, there is no letup in the 47-year effort to hunt down and destroy gypsy moths, which could defoliate trees by the thousands if the invasive moths ever gain a foothold in this state. The gypsy moth program is run by the Washington State Department of Agriculture. See also “Priority Species,” Washington Invasive Species Council.
The volunteer search for European green crabs in Puget Sound actually started with limited surveys more than 20 years before the first green crab was spotted on San Juan Island in August of 2016. Washington Sea Grant had taken over formal management of the program the year before — in 2015 — after green crabs had established a breeding population in Sooke Basin, west of Victoria, B.C. That Canadian site is just across the Strait of Juan de Fuca from Washington’s Dungeness Spit.
In August, it will be five years since the beginning of the Puget Sound invasion, and I asked Emily what she has learned along the way. One thing, she said, is the “value of doing your homework,” such as checking out all your assumptions.
For example, it was once assumed that the Puget Sound invasion began with crab larvae drifting across the Canadian border from the infestation in Sooke. But genetic studies revealed that the population on the Dungeness Spit was far more similar to green crabs found along the Washington Coast. With that in mind, researchers were able to connect that invasion to occasional oceanic currents that flow inland along the south side of the Strait of Juan de Fuca, opposite to the normal outflow. Such “reversals” are capable of bringing crab larvae into Puget Sound, although Canadian crab populations appear to be the source for some invasions on this side of the border.
“How green crabs were getting into the Salish Sea was not expected,” Emily said. “That reminds me that it is always worth checking our own assumptions to make sure that we are doing the right thing.
“When people talk about invasions, the only surprising thing is when there are no surprises,” she added. “Surprises are the rule, not the exception.”
Emily says she has also learned the value of meaningful collaborations. With respect to green crabs, many experts from a variety of agencies as well as community members have contributed knowledge, innovations and new ideas to the effort of protecting the Puget Sound ecosystem.
“No one person is better situated than another,” she said. “If you’re not talking and working together in good faith, you risk missing something and not seeing the full picture.”
Top graph shows average annual catch rate of European green crabs per 100 trap sets since 2015. Bottom graph shows percentages of the total crabs trapped each year at selected sites. Graphic: Washington Sea Grant

While the pandemic blunted the Crab Team’s efforts and put volunteer recruitment on hold last summer, more than 90 percent of the identified trapping areas were covered through an intensified effort of team members following strict pandemic protocols (Salish Sea Currents, May 21, 2020). More than 11,000 traps were deployed, as team members also confronted a relatively new invasion discovered during the fall of 2019 in Drayton Harbor, a mile south of the Canadian border.
A new management team, led by Chelsey Buffington of the Washington Department of Fish and Wildlife, captured 255 crabs in Drayton Harbor last year. That’s more green crabs than the total captured at all the inland sites the previous year.
“All of the mud slogging and crab wrangling was done almost exclusively by the three dedicated crew members: April Fleming and Lindsey Parker, seasonal technicians with Washington Department of Fish and Wildlife, and Allie Simpson, the local coordinator of the effort working with Northwest Straits Commission,” Emily wrote in her extensive Crab Team Blog post at the end of the year.
A key finding was that green crabs in Drayton Harbor were concentrated in a few locations, rather than being dispersed throughout the harbor. Now the hope for Drayton is that it will follow a pattern that has apparently created a favorable trend for Dungeness Spit. There, a heavy trapping effort over three years reduced a large number of crabs down to just three caught last year in 1,883 trap sets.
An even larger infestation last year was seen in Lummi Bay near Bellingham (south of Drayton Harbor), where crabs were first discovered in 2019. The population growth in Lummi Bay was so rapid that a trapping effort, led by the Lummi tribal biologists, caught more than 2,500 green crabs last year. That includes a large number of younger crabs that showed up in August and September. Most of the crabs were caught within a 750-acre sea pond, an artificial water-impoundment used to support nearby salmon and shellfish hatcheries.
“The sea pond appears to be, in some ways, a nearly perfect incubator for green crabs,” Emily said in a story published in Northwest Treaty Tribes magazine. “The enclosure protects the site in such a way that it creates conditions we don’t really see on that large of a scale anywhere else. It’s quite shallow but retains water all of the time, and it’s very protected from a lot of other conditions that might make it hard for green crabs to survive.”
Volunteer training resumed this year, with the trapping effort underway in early April. So far, a relatively few crabs have been caught in Drayton Harbor, Dungeness Spit and Samish Bay.
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