Vanessa Ball | 05.23.2016

Geography | Crab Life Cyce | Widespread Effects | How You Can Help

Growing up in the Pacific Northwest, I tell people that there was a time when I couldn’t stand to eat even one more piece of Dungeness crab. My father used to run us out into the choppy, cold, gray waters in a small open motorboat. As we perched on our wooden-plank seats, we’d raise our feet in mock terror as countless crabs that he pulled from his pots scurried over the boat floor. The crab was plentiful and easy to get, so we ate it frequently as kids. Too frequently, for my taste. Now, although my love of crab has returned, the abundance that I knew in my childhood is threatened. Dangerous increases in carbon emissions are threatening the waterways on which so many people rely for fresh seafood. As a result, the salmon, oyster, and crab that have come to define the Northwest are facing decreasing pH levels that endanger the very ability of these animals to live and reproduce.


The Salish Sea is the expanse of water that begins at the mouth of the Strait of Juan de Fuca, extends east and south into the waters of Hood Canal, and east and north to include the far end of the Strait of Georgia and Desolation Sound. The inland marine waters of southern British Columbia and northern Washington are included in this single estuarine ecosystem. The name Salish is an acknowledgement of the many tribes of First Peoples who have lived on the shores of the inland sea for many millennia and who share historical use of the coastal Salish language. The region is best understood as one enormous estuary. The interaction between the nearly 42,000 miles of rainfall drainage entering the sea mixed with the Pacific Ocean that flushes through the Strait of Juan de Fuca creates an endlessly circulating mix of freshwater and saltwater. Each year, in what is an enormous transfer of water, the entire volume of the sea is exchanged with the Pacific. And under the waves, a vastly differentiated variety of habitats exists. The sea floor ranges from glacially defined rock walls, rock piles generated by seismic activity, glacial moraines, long muddy bays, and jutting rock spires.

Crab Life Cycle

Dungeness crab flourishes here. Individual crabs take advantage of multiple habitats as they progress through their lifecycle. After mating, fertilized eggs are attached to the underbelly of the female crab for several months as they develop into free-swimming zoea. The zoea stage lasts for two to three months depending on prevailing water temperatures, after which a megalope is formed that looks very much like a tiny crab. In all, it takes a year of growth for a crab to reach the juvenile stage. A juvenile crab will slowly increase in size over one to two more years, molting numerous times before reaching reproductive maturity and adulthood.

A Dungeness crab is most vulnerable during the molt, when it sheds one shell and slowly grows another. It molts a minimum of ten times before it is fully grown. When small, a crab will seek shelter in the shells of small bivalves; as it grows larger, it move to eelgrass habitat where numerous varieties of prey can be found. The eelgrass also provides protection from other larger predators like coho and Chinook salmon, rockfishes, seals, and even octopuses. Mature Dungeness crabs will often move to muddy near-shore flats when fear of predation is reduced due to size, speed, and the development of pincers. These adults crabs are harvestable, and they are highly prized by commercial and sport fishermen alike.

With a harvest worth $80 million in 2014 in Washington alone, the crabbing industry is the highest revenue fishery in the state. Yet pollution in the form of increasing carbon emissions is threatening crabbing in the Salish Sea in a frightening way. The Pacific Ocean, and the West Coast in particular, are significantly affected by the increasing carbon dioxide (CO2) in the atmosphere. Surges of deep, cold waters called upwellings rise toward the shore and cause the ocean water to absorb higher concentrations of atmospheric CO2, thereby making the water more acidic. Ocean water that is outside of a normal pH range presents significant challenges for sea life, from inhibiting exoskeleton production to depressing metabolism.

In a report released this spring in the journal Marine Biology, NOAA Fisheries' Northwest Fisheries Science Center in Seattle has confirmed that declining pH will harm the shellfish and crustacean industries. When crab larvae are exposed to lower pH, they take longer to develop, potentially exposing them to predation, and therefore reduced survival rates. Also, they may not have sufficient food available at the right time. The Dungeness crab population will continue to shrink, which will likely mean an icon of the Pacific Northwest dinner plate will become very scarce. In a stark window into what the future may hold for recreational crabbers, a crabbing run with my father last summer netted one lone crab, a drastic change from years past.

Widespread Effects

Salmon and oysters are also being affected. Oysters face many of the same challenges as crabs: with lower pH, the ability to calcify (to form a shell) becomes reduced. Fewer oyster juveniles are being seen in places like Willapa Bay and other key oyster harvesting locations, and ocean acidification is being discussed as a culprit. And then there are trickle-down effects that will negatively impact other species. As much as 30% of Salish Sea marine life may be affected by the decreased pH. Salmon, already vulnerable, will likely see a reduction in their food supply, the tiny shell-forming pteropods they eat.

While we celebrate the removal of the Elwha dams, and thousands more salmon return upstream in numbers not seen in decades, the time those salmon spend in the sea poses significant challenges to survival. Studies have shown that as pH lowers, baby salmon are smaller and less able to smell the water, potentially affecting their ability to return to spawn upriver. And as they mature, these same salmon are less able to use oxygen to exercise, affecting their ability to evade predators, migrate, and spawn successfully.

Salmon runs already face an uphill battle in restoration. For the first time in 30 years, Washington State Department of Fish and Wildlife (WDFW) and tribal fisheries failed to come to an agreement on the 2016 salmon fishing season. The state and tribes normally request a joint permit from NOAA, required in waters like the Salish Sea where there are fish protected under the federal Endangered Species Act. Low projected runs of coho made finding an agreement difficult. The coho run is down to 256,000, much lower than the 2015 prediction of 891,000. Chinook runs are also expected to be down at least 20 percent from 2015. Poor ocean conditions are being blamed for both of these losses in fish. Managers from both groups finally reached an agreement in the final days of May after weeks of meetings to resolve their differences. This challenging process epitomizes the difficulties of protecting and managing conservation efforts in an area complicated by transnational waters, treaties with Native American tribes, robust commercial fisheries, and major port cities.

How You Can Help

Ocean acidification is a major global problem that is not easily solved at the local level, although local actions can make a big difference. Local engagement at the individual, city, and state level will be necessary in order to stem the threat to this critical ecosystem in our region. Beyond working to lead a less carbon-intensive lifestyle, taking action means eating sustainably-harvested seafood, attending city council meetings, holding local officials accountable for events like city sewage leaks, and asking state legislators for their solutions to help reduce carbon emissions and other forms of pollutants. As we feel the growing impacts of a changing climate, we must push for our elected leaders to take a stand.

Another low-effort way to get involved is to follow the Northwest Straits Commision, an organization working on marine conservation in the Salish Sea. One of their current initiatives, #CatchMoreCrab, has educational information on how to reduce lost crab pots. According to their research, "an estimated 12,000 crab pots are lost each year in Puget Sound, and these derelict pots trap and kill approximately 180,000 harvestable crabs."

My children are old enough to come crabbing with me now, and I'm looking forward to bouncing over the rough water in a rickety boat with my dad once more. This time, I'll be the one scooping up the pots and listening to little children scream with delighted terror and excitement. And after we've warmed up, we'll enjoy a messy dinner drenched in melted butter out in the backyard. I just hope there's still enough crab to go around.


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