Spring migration is in full thrust at Humboldt Bay. Every day tens of thousands of shorebirds are arriving to rest and feast in the mosaic of wetlands and intertidal mudflats that make up this stretch of California coastline. Located 260 miles north of San Francisco, the area is the second-largest estuary on the West Coast and one of the state’s most productive bodies of water­—its tides act like lungs, constantly draining, refilling, and replenishing nutrients. Among the various habitats supported by this ebb and flow are half of California’s remaining eelgrass beds, a vital food source and habitat for herring as well as migrating birds.

This combination of size, biodiversity, and increasingly rare habitat is what makes Humboldt an essential stopover site for about 50 species of birds on their seasonal flights between Mexico and northern breeding grounds. Nearly half the Dunlins and 23 percent of all Western Sandpipers pass through every year.

Meanwhile, Pacific Black Brants wheeling in from Baja, California, land feet first in the shallow waters of the northern part of the bay, the biggest contiguous bed of intertidal eelgrass between Mexico and Washington state. Up to 60 percent of Brants break up their seasonal journey to Alaska at Humboldt, where eelgrass is the mainstay of their highly specialized diet.

Soon, though, Brants, American Wigeons and other water birds dependent on these eelgrass beds might be facing a threat: expanding shellfish farms. Oyster farming in Humboldt Bay could nearly double following approval of a controversial proposal submitted by Coast Seafoods Company. The Humboldt Bay Harbor, Recreation and Conservation District Board of Commissioners voted 4-0 in February to allow the company, based in Bellevue, Washington, to add 256 acres of oyster aquaculture to the 300 acres it is already farming in northern Humboldt Bay.

To prevent this development, The National Audubon Society and the California Waterfowl Association sued the Humboldt Harbor District in a lawsuit filed March 30 by Earthjustice, which represents the Audubon Society and Waterfowl Association. The action targets the environmental impact studies forming the basis for the district’s approval of Coast Seafoods’ expansion. 

The Pacific Black Brant is one of two subspecies in North America. Nathan Graff/USFWS

Coast Seafoods grows oysters on long lines strung between PVC pipes embedded in the bottom of the bay. The pipes, spaced between 2½- and 10-feet apart, curtail eelgrass growth and can damage as much as 90 percent in the beds they occupy. At high tide, the pipes are completely submerged, but when the bay waters ebb, the pipes stick out like a copse of cluttered stumps. Boats, machines, and humans involved in oyster farming add to the damage, disturbing the Least and Western sandpipers that depend on these open bay waters to avoid predators, says Anna Weinstein, Audubon California’s marine program director. What’s more, Brants won’t even go into areas with structures, she says.

Audubon and the California Waterfowl Association have been working since 2015 to meet with the project developers to discuss relocating aquaculture expansion to areas less sensitive for wildlife. Coast Seafoods’ 300-acre oyster farm operating in the north bay has completely destroyed eelgrass in some places and damaged it in others, Weinstein says. The company’s original proposal would have tripled its shellfish farm in Humboldt Bay, but when waterfowl hunters publicly protested, the Harbor Commission revised the plan.

Audubon is not opposed to aquaculture, says Weinstein, but it hopes to reduce the footprint and relocate it to parts of the bay less critical to Brants and other wildlife.

The plan the Harbor District approved would add 165 acres of long-line oyster culture with pipes spaced 10 feet apart. If the company meets a series of specific requirements designed to monitor the expansion’s environmental impacts, a second phase would allow oyster farming on another 91 acres.

Despite this tiered approach, the plan will have unacceptable effects on birds and eelgrass, said Brigid McCormack, former executive director of Audubon California. Adding 256 acres of new shellfish farming represents an “unprecedented expansion” that will dramatically increase the footprint of existing oyster operations, she said. “Humboldt Bay constitutes a delicate balance of habitat, recreational opportunities, and economic activity—and this project will turn all of that upside down.”

Eelgrass beds near oyster lines in Humboldt Bay. Anna Weinstein

According to Audubon’s case, the final report failed to analyze the cumulative effects of this and other shellfish farms approved for Humboldt Bay. In addition to the Coast Seafoods expansion recently approved, other oyster farming proposals would result in a total of 800 acres of Humboldt’s sensitive habitat being occupied, Weinstein says.

Along with birds, Audubon and Waterfowl Association officials are also concerned about Pacific herring, a foundational forage fish that spawns in the bay. A decline in herring would contribute to losses in fish, bird, and mammal species, according to the lawsuit.

For now, at least, the Brants, Wigeons, and other migrating birds can continue to feed on Humboldt’s rich bounty of eelgrass, putting on the weight they need to continue their long flights north, where they will spend the summer raising their chicks. To keep it that way, Audubon plans a vigorous legal challenge to prevent the Harbor District’s approval of the oyster farming expansion, and to ensure that any future expansion avoids the vital eelgrass habitat and other areas critical to wildlife. At stake are an ancient migratory tradition, birds, and the most significant eelgrass beds on the West Coast.

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