Geoduck Aquaculture: A Brief Review


Sara Thompson

There are 65 miles of waterfront on the Key Peninsula. Less than 2 miles are currently farmed. Statewide, about 60 percent of tideland is privately owned. Those who own tideland can apply for geoduck farming permits. The permit approval process requires multiple levels of review and takes two to five years, including appeals.

The density of native geoducks in south Puget Sound varies from 0-22 per square meter, with an average of 1.7. The density in geoduck farms is about ten per square meter. They are harvested in about five years. In nature geoducks can live up to 150 years.

The basics of farming:

—Geoduck seed is planted in tubes placed at a density of about one per square foot.

—Solid PVC tubes have mesh rubber banded over the top or a net canopy to protect the young geoducks. Mesh tubes do not need to be covered.

—Tubes are removed after about two years when the geoduck is deep enough to be safe from predators.

—Geoducks are harvested after about five years using high-flow, low-pressure hoses.

Aesthetic concerns:

—Tubes and netting: Present for the first two years and visible during the summer months about 20 percent of the time (low tide) from the beach.

—Gear that floats away: Noted as a problem especially in the early to mid-2000s. The recent use of mesh tubes has reduced loss. Companies are required to monitor farms closely, and to have their gear tagged.

—Work on the farms and harvesting is usually accessed from the water and there are requirements to minimize noise and light impact on neighbors.

Environmental concerns:

—Concerns have been raised about the use of PVC tubes, the effects of monoculture, loss of eelgrass, disruption of native species at the time of planting, and geochemical effects.

—PVC tubes appear to be safe. The material is inert, and sediment near the tubes has not shown any evidence of micro plastics, according to experts testifying on behalf of Longbranch Shellfish at the Shoreline Hearing Board appeal in 2014. There is no evidence that the tubes or debris from the tubes, which sinks to the bottom of the sound, would harm fish or birds.

—Sea Grant, a collaboration between the University of Washington and the federal government, commissioned a research program to explore these issues starting in 2007, and results were published in 2013. Although there were some shifts in the distribution of various species, the overall animal community did not differ significantly between geoduck farms and adjacent beaches.

At one site in Samish Bay, eelgrass (an important salmon habitat) was affected by both the presence of protective gear and harvesting. It recolonized over the course of a year, but it is unknown what might happen with the replanting and harvesting that would occur on a farm.

Geoduck farming leads to a small accumulation of nitrogen and phosphorous in the sediment, which is released at harvest. However, researchers noted this amounts to about 0.001 percent of the daily load from streams or wastewater plants.

What remains unanswered is the question of cumulative effect. Geoduck farming is still new and the impact of continued planting and harvest is uncertain.

In an interview with the KP News in December 2014, P. Sean McDonald, Ph.D., a UW researcher working with the Sea Grant program, said, "The Puget Sound shore is a hard place for the animals that live there. Storms, surf and flooding may be as disruptive to their environment as geoduck farming. But we need to understand if there is a tipping point, where the effects over time or due to increased extent are causing harm to our beaches."