Oysters: the ecological danger behind the plate

By Envision Magazine on May 4, 2014

 

Story by Barbara Marty and Virginia Werner
Contributed reporting by Paula Wright
Photography by Sian Joan Kavanagh

  

Along the Pacific Coast, oyster populations have plummeted over the past two centuries, destabilizing formerly rich and complex marine ecosystems. Its national success among seafood lovers hides a more preoccupying reality. The preservation of wild populations like the Olympias is now at stake and the fight for an oyster rebirth combines the efforts of environmentalists, oyster farmers, and restaurant owners of the Pacific Northwest.

Native oyster supplies began to dwindle in the mid-1800s. Having exhausted oyster beds in the Bay Area, shipments were ordered from farther north along the coast. But other issues, such as siltation and habitat degradation combined with heavy harvests, plagued the oysters. Commercial expeditions and fisheries recorded dwindling yields at the turn of the 19th century. Unable to turn a profit because of the low yields, harvests dwindled and fishing pressure reduced.

A variety of factors that disrupt the productivity and scope of oyster grounds have been to blame for the lack of recovery in oyster populations. Aside from overharvest, other limiting factors such as habitat degradation from rising siltation levels, competition from other species, and predation by invasives have challenged the oysters’ ability to restore populations to pre-settlement levels.

  

  

The global demand for oysters continues to rise while wild oyster populations have sharply declined. Once a vital player in estuarine ecosystems and abundant from Baja California to Southeast Alaska, native oysters have diminished to “functionally extinct” levels and are believed to no longer play a crucial role in their own ecosystem in the wild.

In the food world, each type of oyster is marked by a different flavor profile, depending on its environment, its age, the season, and the way the oyster has been raised: in the wild or artificially. Gabriel Drake, an oyster shucker at the Dan & Louis Oyster Bar in Portland, Oregon, explains that some varieties are sweeter than others because of their age. The Hama Hama Farm supplies the oyster bar with a sweet, Sea Cow variety which, unlike most oysters, is grown for five to six years before harvest.

Located directly next to the Hamma Hamma river in Washington, the Hama Hama commercial farm and distributor mainly operates out of the Hood Canal, where they annually harvest hundreds of thousands of oysters. Hama Hama ships to restaurants and other clients local and nationwide.

  

While commercial farms like Hama Hama depend on their farmed populations to produce natural larvae sets in order to preserve genetic diversity, both farms and conservation projects import oyster seedlings from commercial hatcheries. But for some oyster growers, viable estuarine habitats have been so scarce and of such variable water quality that some oyster farms have had orders for oyster seedlings unfilled. 2005 marked a change in estuarine viability for a number of oyster growers.

 

  

That year, the Whiskey Creek Shellfish Hatchery in Netarts Bay, Oregon, experienced a near 85 percent loss of total oyster larvae yield. This and other hatcheries struggled in succeeding years to produce oyster seed for commercial operations.

In 2009, in partnership with researchers at Oregon State University, Whiskey Creek discovered that lower pH levels in the ocean water that supplied hatchery tanks was to blame. Commercial oyster farmers began to realize that they were experiencing the effects of ocean acidification first-hand.

Then, OSU researchers discovered that acidified water affects oysters at the larval stage by impeding proper shell formation. This in turn leads to a shorter lifespan for the oysters.

With advanced equipment, oyster hatcheries are now able to monitor ocean acidification levels and turn off water pumps when the pH becomes too low. Other commercial oyster farms attempt to offset acidification by using additives to restore the pH levels in hatchery tanks.

Monitoring of pH is not the only route oyster breeders have taken to address the issue.  Commercial operations like the Hama Hama Farm rely on a complex system in order to thwart natural threats to the young oysters. “We are creating a current that allows us to grow them in densities that we wouldn’t be able to achieve outside of the farms,” says Adam James, the Operations Manager at Hama Hama.

Hama Hama uses a “combination of organic shapes and grid lines” to plan out planting and harvesting, explains James. Once the young oysters have grown past the stage in which they are the most susceptible to ocean acidification, they are attached to discarded oyster shells and hung on ropes off docks along the Hood Canal to allow them to grow in nurseries for protection against predation. Mature oysters are then transferred to sites throughout the area. Oysters with seedlings attached on the outer shell (cultch shells) are then planted in the bay area. The oysters’ growth process is monitored to ensure they develop without exposure to stressful environments.

Clean water means healthy shellfish, which in turn means happy customers. For hesitant consumers, the word “farmed” often resonates with artificial and unhealthy products linked with the food-processing industry. However, while farm-raised fish are often exposed to antibiotics and other chemical treatments, farm-raised oysters have proved to be a  viable ecological alternative to their wild peers.

With this being the case, oyster farms have advocated for the Clean Water Act, for low environmental impact development, sewage improvement, and owners have been members of conservation boards.The farm provides a well rounded ecosystem, where not only oysters but seals, seagulls, small crabs, and fish thrive.

Unlike farm-raised fish, oysters do not need to be fed by the farmers. Instead, oysters filter minerals and nutrients from the water they grow in and thus improve marine ecosystem water quality.

This is why farmers like Hama Hama do not use any chemicals during the whole production process and are engaged in the protection of the coastal ecosystem.

In the future, the farm hopes to expand as it deals with the changing ocean conditions. “We want to create a product that is iconic and sustainable,” says James. “People will rally for the food they eat. The human connection to plants and animals is a powerful force.”