Groundbreaking Research on One of the World’s Largest Burrowing Clams

Written by on December 20, 2013 in Marine Life, Other Marine Life

A new report released last month by Washington Sea Grant (WSG) on geoduck aquaculture increases understanding of how industry operations might affect Puget Sound and Strait of Juan de Fuca environments. The findings help answer key questions, identify data gaps, and prioritize future research. It also examined the impact that geoduck farming has on wild geoducks, intertidal ecosystems, and other local species.

Adult geoduck. Photo courtesy of Washington Sea Grant.

Adult geoduck. Photo courtesy of Washington Sea Grant.

The Pacific geoduck (Panopea generosa) is one of the world’s largest burrowing clams. The average geoduck weighs between one and three pounds and its shell can reach up to 10 inches in length. They’re siphons can extend about three feet, a feature that allows them to burrow beyond the reach of most predators.

Geoduck harvesting is an $80 million industry in British Columbia and Washington State, which provides nearly half of the world’s supply of geoduck meat. Commercial harvesting of wild geoducks dates to the 1970s. Initially, geoduck farming began due to concerns that the wild stock was being overharvested because it was difficult to monitor and there was a growing black market for geoducks.

“The idea had been that if we figured out a way to grow these things in a farm setting, it would take pressure off wild geoducks and allow the population to stabilize,” Sean McDonald, one of the primary investigators, explained to MST over the phone.

Lately, geoduck farming has expanded greatly. Farming in Washington has several benefits: geoducks are a local species and don’t require a huge input of energy, they reach market-size in only four to seven years, and they look better than wild geoducks.

“Farms are able to grow clams that are better for the market…they have characteristics that are prized in the restaurant world,” McDonald said. “And growers get a good price for the product.” They can get up to $100 per pound overseas.

Juvenile geoducks. Photo courtesy of Washington Sea Grant.

Juvenile geoducks. Photo courtesy of Washington Sea Grant.

In 2007, due to the increasing interest in farming, the Washington State Legislature asked WSG to review existing literature and initiate original research to learn more about geoduck aquaculture.

Overall, shellfish farming is much more stable than farming finfish, like salmon, which require a huge input of energy (in terms of food) and have been associated with major disease problems. On the contrary, shellfish farms can actually benefit the local ecosystem by removing nitrogen and other nutrients.

In this case, McDonald told MST that the concern and the reason for the study “is more with the practice than the shellfish themselves.”

Here’s how geoduck farming works:
Baby clams are planted in the beach in high densities and then covered with PVC tubes and nets for protection. They remain covered for one to two years and then the nets are removed. After four to seven years, the market-sized clams are removed individually by hand, using a jet of low pressure water to displace the sand, allowing a person to gently pull them out.

Aquaculture structures. Photo courtesy of Washington Sea Grant.

Aquaculture structures. Photo courtesy of Washington Sea Grant.

The potential problem is a series of small disturbances, most of which are social, rather than environmental, McDonald explained.

“The beach itself is disturbed – the farm changes the structure quite a bit,” he said. So a beach that was once available to the public becomes unusable.

Harvesting geoducks at low tide. Photo courtesy of Washington Sea Grant.

Harvesting geoducks at low tide. Photo courtesy of Washington Sea Grant.

“There is also concern about the high density when they’re grown. But what probably causes the most issues is the harvest, stirring up sand and flushing a lot of small animals out of the beach and sand,” McDonald said.

Most of these effects are short-term. The long-term effects of continued farming in one location are a topic for future research.

WSG also released a review of more than 420 peer-reviewed papers on shellfish aquaculture. The report and the review provide recommendations for future research and monitoring approaches to support sustainable geoduck aquaculture in Puget Sound and the Strait of Juan de Fuca.

“Overall, the effects are fairly minimal. Some of the critters are affected negatively, some positively,” McDonald said.

A beach is already “a tough neighborhood.” Those animals have to deal with exposure and being constantly pummeled with waves. The kind of disturbance from geoduck aquaculture is pretty minimal compared to that.

You can read the final report here: Geoduck Aquaculture Research Program.

Copyright © 2013 by Marine Science Today, a publication of Marine Science Today LLC.

About the Author

About the Author: Emily Tripp is the Publisher and Editor of MarineScienceToday.com. She holds marine science and biology degrees from the University of Miami's Rosenstiel School of Marine and Atmospheric Science and a Master of Advanced Studies degree in Marine Biodiversity and Conservation from Scripps Institution of Oceanography. When she's not writing about marine science, she's probably running around outside or playing with her dog. .

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