The Deep Dive on Geoducks

This post was originally published on SEATOR social media on October 1, 2018.

We receive many shellfish samples at the SEATOR lab, but one of the most remarkable is definitely the geoduck. If you’re not familiar with this species, you may find them quite strange-looking, and not know that they are pronounced “gooey duck.” However, there is much more to geoducks than their interesting appearance; their story becomes even more fascinating the deeper you dive in.

Geoducks (Panopea generosa) are the world’s largest species of burrowing clams, and they are native to the west coast of North America, from California all the way up to Southeast Alaska.  They are found in muddy or sandy sediments, through which they can burrow as deep as 1.3 meters below the surface, with their long siphon stretching up to the seafloor.  Accordingly, the name geoduck is believed to come from the Nisqually Indian word gweduc, meaning “dig deep.”  Beds of geoducks can be found in shallow waters, or in water as deep as 100 meters.  Like other clams, they are filter feeders, and their siphon brings seawater and the floating particles of food and oxygen it contains down to their home in the substrate and expels filtered sea water through the other side.  These clams also have a very long lifespan, as they can live to be over 150 years old. 

In addition to their impressive biology and lifestyle, geoducks are also revered for their taste. In Asian markets, the geoduck’s exotic appearance and delicate texture has made it a delicacy.[1] In China in particular, where geoducks are known as ‘elephant trunk clams,’ ordering an impressive and expensive food like the geoduck is seen as a status symbol.[2] Customers in Chinese restaurants will thus pay $150 per pound of geoduck, and the growing middle class creates rising demand for such prestigious foods.[3] In Southeast Alaska, British Columbia, and Washington, a lucrative commercial harvesting industry has developed to meet the growing demand, with 90% of harvested geoducks being exported to Asia.[4] To harvest the geoducks, fishermen scuba dive to the seafloor, loosening the clams with a spray hose and collecting them by hand; the clams are also commercially farmed on tidelands.[5] The landed value of geoducks is $10/lb. and the average adult geoduck weighs 1-3 lbs. with some individuals weighing up to 6 or 7 lbs.., so a skilled geoduck diver can collect a harvest worth thousands of dollars in only a few hours.[6]

Geoduck fisheries are highly regulated, yet given the opportunity for such immense profits, poaching and illegal harvesting activities is a real threat.[7] While fish and wildlife officers enforce strict legal harvest limits, the ways to skirt these rules abound: harvests can be underreported with false records, extra clams collected can be hidden in boat hulls, and clams can be taken at times or places where harvest is prohibited, such as during the night or in polluted areas.[8] Monitoring for poaching and illegal activities is extremely difficult and remains an ongoing challenge.[9]

In Alaska, another significant risk associated with geoducks are that they have been found to have high levels of toxins that can cause Paralytic Shellfish Poisoning, or PSP.[10] This creates a serious public health concern as well as considerable challenges for commercial geoduck fisheries in Alaska, which experience significant uncertainty in the face of high variability in toxin levels and substantial economic losses when they must close or delay harvest due to PSP toxin levels that are too high. That’s what brought these geoducks to the Sitka Tribe of Alaska Environmental Research Lab (STAERL). We are testing the clams for PSP toxins as part of an ongoing research project that aims to provide scientific information on the distribution and life cycle dynamics of Alexandrium, the phytoplankton that produces these toxins. With increased understanding of the relationship between these phytoplankton and the toxicity of geoducks, the aim is to provide resource managers with knowledge that will allow them to improve and adapt geoduck management and harvesting practices to better protect public health and enhance economic stability for the industry.

Research Partners: University of Alaska Fairbanks (UAF), Sitka Tribe of Alaska (STA), and industry partners (SARDFA).

Geoducks are truly a treasure of the Pacific Northwest coast. Learning more about how harmful algal blooms create conditions of toxicity is one necessary step towards reducing the vulnerability of the geoduck fishery, with benefits to both harvesters and consumers. It won’t solve all the threats to the geoducks, including maintaining sustainable and ecologically sound management when there is tremendous incentive for illicit activity to profit from the geoducks’ culinary celebrity, but it will significantly help geoduck managers and divers bring safe seafood to market—and who wouldn’t want to want one of these beautiful creatures on their plate?


Sources:

[1] https://www.bbc.com/news/magazine-33261666

[2] https://www.bbc.com/news/magazine-33261666

[3] https://www.bbc.com/news/magazine-33261666

[4] https://www.smithsonianmag.com/science-nature/geoducks-happy-as-clams-52966346/, https://www.bbc.com/news/magazine-33261666, https://www.pbs.org/newshour/science/demand-super-sized-clams-keeps-poachers-cops-busy

[5] https://www.smithsonianmag.com/science-nature/geoducks-happy-as-clams-52966346/, https://www.pbs.org/newshour/science/demand-super-sized-clams-keeps-poachers-cops-busy

[6] https://www.bbc.com/news/magazine-33261666, https://www.pbs.org/newshour/science/demand-super-sized-clams-keeps-poachers-cops-busy, http://www.adfg.alaska.gov/index.cfm?adfg=geoduck.main

[7] https://www.smithsonianmag.com/science-nature/geoducks-happy-as-clams-52966346/, https://www.pbs.org/newshour/science/demand-super-sized-clams-keeps-poachers-cops-busy

[8] https://www.smithsonianmag.com/science-nature/geoducks-happy-as-clams-52966346/

[9] https://www.pbs.org/newshour/science/demand-super-sized-clams-keeps-poachers-cops-busy

[10] http://www.adfg.alaska.gov/index.cfm?adfg=geoduck.main

Image Sources:

https://www.todayonline.com/lifestyle/food/geoduck-farming-takes-demand-clams-grows-asia

http://www.geoduck.org/

https://www.opb.org/news/article/geoduck-farming-heddy/

https://www.pbs.org/newshour/science/demand-super-sized-clams-keeps-poachers-cops-busy

http://o.seattletimes.nwsource.com/html/localnews/2018041537_geoduck22m.html

https://www.seattleaquarium.org/blog/all-about-geoducks

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