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Sunday, December 10, 2023
Dec. 10, 2023

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Dungeness crab dying amid low oxygen levels linked to climate change


Terry “Chop” Arnold Jr. remembers the first few times he climbed in his dad’s 36-foot fishing boat at an old log boom, near the northernmost tip of Washington.

“I started going out with him when I was 10,” said Arnold, a Makah tribal fisherman. “And I never looked back.”

For decades, Chinook salmon were plentiful along the beach, he said. But in the ‘90s, the Arnolds had to trawl as far as 30 miles offshore to find fish.

Fishing for many species has proved pretty steady over the years for Arnold. But lately, there have been seasons where there’s little or no crab, he said.

Not too far down the coast, piles of dead Dungeness crab washed ashore on Kalaloch Beach this summer. Meanwhile, fishers have shared stories about hoisting up dead or suffocating crabs in their pots, said Jenny Waddell, research ecologist with the Olympic Coast National Marine Sanctuary.

Now, scientists are working to understand how climate change is affecting Dungeness crab, which is both culturally significant and a pillar of Washington’s seafood industry. From 2014 to 2019, coast-caught Dungeness was worth an annual average of $45 million.

Last week, the National Oceanic and Atmospheric Administration announced a $4.2 million award for a four-year study on Dungeness crab and krill that will bring together researchers and experts from coastal tribes, public universities and federal agencies from Northern California to Washington.

Climate change has been exacerbating existing marine environmental stressors through changes in temperatures, ocean chemistry and seasonal cycles.

The ocean absorbs about 30% of the carbon dioxide released in the atmosphere, primarily from human activity. Increases in the gas in the ocean have led to rising acidity. Studies have shown as acidity rises, shellfish struggle to maintain hardy shells, their growth slows, and death rates rise.

Over the last 20 years, the Olympic Coast sanctuary in Washington has monitored a changing marine environment. Where there’s typically vertical mixing to distribute nutrients, at times ocean waters have become stratified, trapping oxygen-deficient, acidic waters against the seafloor, Waddell said.

Marine animals need oxygen to survive.

Along the Pacific coast, Dungeness crab live in the intertidal zone out to a depth of about 560 feet. Washington’s coastal commercial crab fishing ground spans from the Columbia River to Cape Flattery near Neah Bay.

There’s plenty of research and real-world evidence that confirms climate change is hurting marine species, said Jack Barth, executive director of the Marine Studies Initiative at Oregon State University.

About a decade ago, Oregon State University researchers confirmed that an increase in ocean acidification was definitively related to the collapse of oyster seed growth at a commercial oyster hatchery.

Meanwhile, harmful algal blooms have led to complete and partial closures of Dungeness crab fisheries up and down the West Coast. The blooms are rapidly growing bunches of algae that can produce dangerous toxins.

The Quileute Tribe declared a fishery resource disaster after an algal bloom shut down their Dungeness harvest in 2015. Since then, they’ve used disaster relief funds to purchase instruments to measure current ocean conditions and start to piece together trends, said Jennifer Hagen, Quileute Tribe marine policy adviser.

The blob, a marine heat wave that wreaked havoc on Northwest fisheries during 2015 and 2016, led to sea bird die-off, poor salmon returns and dozens of closures.

“We’ve had these catastrophic events like the heat blob and things that are showing us that things are changing,” Hagen said, “and they’re not changing incrementally.”

But scientists still don’t have a good handle on how organisms are affected by multiple stressors. What happens when crabs are faced with algal blooms, low oxygen and warm water?

Researchers hope to start to figure that out in the next four years.

They plan to map out where the lowest concentrations of oxygen lie and where the warm water is, and find where these stressors intersect to make life even more hostile for the species, said Richard Feely, senior scientist at NOAA’s Pacific Marine Environmental Laboratory.

They’ll collect and synthesize historic and present-day data, and traditional ecological knowledge from coastal tribes, with that of academic and federal research institutions.

“We can have a voice,” said Hagen, the Quileute biologist, “where we can take our knowledge — because we’re here, we exist here in this area on the crab grounds — and that knowledge is being given value.”

The Quileute tribe sent a letter in support of the research proposal, and Hagen said she hopes they can be deeply involved.

“I just think that’s a nice addition not only because it connects with the coastal people who have been here forever,” Barth said, “but our instrumental records only go back 50, 60 years. So we’re looking for a collaborative effort, with their knowledge of the changing seasons, where and when they’ve been able to make good use of the fishery.”

The research will combine data, modeling and laboratory experiments to paint a better picture of where the effects of climate change overlap, the causes and the biological impacts when combined, Feely said, in an aim to help inform future fishery practices.

The research is welcome for people like Arnold, the Makah fisherman, who rely on the ocean for sustenance.

“We’re all connected by water, some way, somehow,” Arnold said. “And the ocean is probably the most important aspect of life for us. If we start losing it, it could be devastating.”

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