digging deep

Walking along Puget Sound’s miles of sandy coastlines, one can expect to find a vast array of sea-dwelling creatures exposed by the ebbing tide. Marvels and oddities abound, prompting tentative pokes and prods from beachcombers and animals alike. But perhaps the most curious creature of them all lies directly underfoot, buried three feet beneath the sand.

The geoduck does not advertise with garish colors or flashy displays; nor does it deviously track down prey or snap menacingly at passerby. In fact, the geoduck (Panopea generosa) does little to betray its presence at all, save for leaving a quarter-sized dimple on the beach at low tide.  It simply stays put, and eats, and reproduces. For a long, long time.

The geoduck is the world’s largest burrowing clam, a bivalve behemoth that can weigh more than ten pounds and measure nearly five feet from shell to siphon. Native to the Pacific Northwest, the geoduck is most abundant in the subtidal regions of Puget Sound and British Columbia. The clam’s distinctive name is derived from the Nisqually word gweduc, meaning “dig deep”.

The shell itself is large but unremarkable; oblong and opaque-white with concentric rings, it can be seven to nine inches long. The mantle and siphon, however, are sights to behold. In all bivalves, the mantle is a membrane that encases the animal’s innards within the shell. A geoduck’s mantle is so thick that the shell cannot fully close, giving the clam a grotesque, bloated appearance.

Bivalves use siphons to both filter plankton from the water for food and excrete waste back out. The siphon of the geoduck is perhaps its most distinguishing feature. Creamy-brown and undeniably phallic, it can stretch nearly four feet from a burrowed geoduck to the seafloor.

Geoducks reach sexual maturity at around three years old. From late April to July each year, females will release more than seven million eggs into the water for males to fertilize. The larvae go through several planktonic stages in the water column before settling on the seafloor after 40 to 60 days. Developing geoducks will burrow down into the sediment at an average of a foot a year, stopping their descent at around three feet.  And that’s it—job’s done.  For the next century or so, the geoduck will remain in this spot, filtering diatoms and other phytoplankton out of the water and growing at about an inch a year. Once the shell reaches its maximum length after ten to fifteen years, the clam continues to widen and put on weight.

The oldest recorded geoduck lived to be a ripe 168 years old. This kind of longevity can be attributed to a life of doing, well, next to nothing. Also, geoducks have few natural predators aside from the occasional sea otter or dogfish wily enough to pry one out. Nothing really bothers to mess with geoducks except humans, of course.

The geoduck has become something akin to a cultural icon in the Pacific Northwest. Shellfish enthusiasts insist that the arduous task of excavating a geoduck is a rite of passage for Washingtonians. The beloved bivalve is Evergreen State College’s official mascot; the school’s Latin motto, Omnia Extares, meaning “let it all hang out”, is a tongue-in-cheek nod to the clam’s phallic appearance.

Geoducks are also a commodity in the shellfish industry, especially overseas. In China and Japan, geoduck siphon, a delicacy prized for its texture and flavor, commands a $30-per-pound price tag.  Since the 1970s, Washington and British Columbia have seen a steady increase in the number of geoduck farms popping up to supply the demand. Geoduck farms feature rows of “predator exclusion devices”, which are basically PVC tubes stuck into the sand to shelter developing clams. These farms have caused considerable tension between shellfish entrepreneurs and Puget Sound residents in regards to shoreline aesthetics and alleged ecological disturbance. Advocates of geoduck farming claim that the clams help clean the water by removing algae diatoms from the water column. The clams ingest the diatoms and are eventually harvested, resulting in a net removal of nitrogen from the marine ecosystem. Less nitrogen means less food for the algae to consume and propagate with. The opposition states that the geoducks’ algae-reducing effects are negligible, and that the diatoms they’re consuming are also the food source of other native bivalves. Also, the rows of PVC pipe on the beach are an eyesore to residents during low tides. The Washington State Shellfish Aquaculture Regulatory Committee has convened with industry leaders and citizen representatives to discuss a regulation agreement.

As all of this controversy roils on the surface, the geoducks lie three feet below, blissfully unaware. One might say they’ve got their heads in the sand—but since they don’t actually have heads, no one really says that.

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