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A previous Ferrebeekeeper post described the largest living bivalve mollusk–the magnificent giant clam which is indigenous to the South Pacific. However there are other large bivalve mollusks out there which are nearly as remarkable (and possibly even stranger looking).  One of these creatures, the geoduck clam (Panopea generosa), causes a unique amount of controversy, pride, consternation, and outright greed along the Northwest coast of North America where it lives

Geoduck Clam (Panopea generosa)

Geoducks are the largest burrowing clams in the world.  Specimens weighing up to three pounds (0.5–1.5 kg) are widely known and 15 kilogram monsters are alleged to exist.  Although the clams’ shells can grow quite large–sometimes exceeding 20 cm (8 inches) in length–the outstanding features of geoducks are their obscene siphons/necks which regularly reach 1 metre (3.3 ft) long (and can reputedly grow to twice that length).  Thanks to these long necks, geoducks can bury themselves deep in the coastal sands while still filtering huge amounts of plankton rich water through their digestive system. .  Geoduck (which is apparently pronounced “gooey duck”) is a word from the Lushootseed language, a tongue spoken by the Nisqually tribe.  It means “dig deep” although the Chinese name for the clams “xiàngbábàng” (which means “elephant-trunk clams”) seems equally apt.

Geoducks of Wasshington and British Colombia do not have many natural enemies (although apparently in Alaskan waters they are preyed on by sea otters and dogfish).  If left undisturbed, the bivalves can live to the fabulous age of a century-and-a-half.  Lately however, the geoducks, which dwell in giant cold-water colonies beneath Puget Sound, are being gobbled up en masse by humankind.  Although Anglo-Saxon settlers to the Pacific Northwest found the suggestive sight of the clams to be unbearable, the mollusks are hugely popular in China and Asia, where price can exceed US$168/lb (US$370/kg). Chinese diners believe that the geoduck’s…manly shape indicates that the unpreposessing mollusk will act as an aphrodisiac for those who consume its flesh. Price has shot upwards as China’s economy has grown.

Wow--Puget Sound is Beautiful.

In order to cash in on this bonanza, aquaculturists are attempting to stake out larger and larger swaths of coastline as geoduck farms. Such use of the tidelands causes consternation to real estate developers. Not only do developers object to the unaesthetic appearance of PVC pipes used as nurseries for juvenile geoducks, but the interests of both parties are entirely opposite.  Coastal land development involves bulkheaded beachfronts, deforested land, and nitrogen waste from gardens and septic systems—all of which are inimical to successful geoduck beds.

As the conflict rages on, some people (figuratively!) embrace the geoduck and its strange appearance for non-financial reasons. The Evergreen State College of Olympia, Washington has adopted the remarkable burrowing clam as a mascot.  Although the school’s official seal features a conifer tree, the unofficial coat of arms features a geoduck rampant d’or on a rondel azure (or however you say that in heraldry speak).  Additionally the school’s teams are all named the geoducks and they actually have a guy dressed up like a giant filter feeding clam to root for them.

"Speedy" the Geoduck--don't even ask about the fight song....

The Zebra Mussel (Dreissena polymorpha)

Since 2011 is already shaping up rather grimly as the year of mass animal die-offs, it is time to revile the black-hearted invasive species which caused some of the the worst mass bird die-off in recent history.  I’m talking about the detested zebra mussel  an inch-long filter feeding bivalve mollusk with a pattern of brown zigzags on its shell.  The freshwater zebra mussel isn’t really that closely related to the marine mussels but shares many features with the Venus clams.

I am not too surprised if you feel ripped off that this dangerous invasive animal is a tiny shellfish.  But don’t dismiss the zebra mussel because of its diminutive size.  Zebra mussels are believed to be the source of deadly avian botulism poisoning that has killed immense numbers of birds in the Great Lakes since the late 1990s.  Additionally US powerplants and boat owners spend half a billion dollars a year scraping the creatures off water intakes for power plants and other underwater equipment.  The mollusks are also rather sharp and can injure wader’s feet–which necessitates wearing shoes in affected waterways.

Originally natives of the Black Sea and Caspian Sea, Zebra mussels spread via canal to the rest of continental Europe and then stowed away in fresh-water ballast and on anchor chains of ocean going boats to travel across the ocean to Great Britain, Ireland, Canada and the United States. The Great Lakes are being hit especially hard by them.  Whenever they spread to a new location the native freshwater mollusks are gravely impacted.

Zebra mussels on a Lake Erie beach (photo from Great Lakes Environmental Research Lab).

Of course the mussels’ impact is not entirely negative.  To quote the National Atlas of the United States (which, by-the-way is an interesting geography resource):

Zebra mussels do have a positive impact on some native species. Many native fish, birds, and other animals eat young and adult zebra mussels. Migratory ducks have changed their flight patterns in response to zebra mussel colonies. Lake sturgeon feed heavily on zebra mussels, as do yellow perch, freshwater drum, catfish, and sunfish. The increase in aquatic plants due to increased water clarity provides excellent nursery areas for young fish and other animals, leading to increases in smallmouth bass populations in Lake St. Clair and the Huron River. However, these native species do not feed heavily enough on zebra mussels to keep the populations under control.

We might as well enjoy the smallmouth bass and the clear water.  Nothing people have done has halted or even impacted the spread of the zebra mussels so it looks like we’ll have to learn to live with them.

Ye Olde Ferrebeekeeper Archives

July 2021