The Managed World: Non-native oysters in the Chesapeake

There is no place on earth, no matter how remote, untouched by humans. We are mighty: we can trawl the deep, explore the South Pole, and fish every single island in the South Pacific. But as every young nerdling knows, with great power comes great responsibility. The Managed World series in the Oyster’s Garter explores the hard choices that come from a human-dominated world.

It’s been a long time since we had a Managed World entry, and it seems appropriate to start again with our namesake, the mighty oyster. Atlantic oysters (Crassostrea virginica) aren’t so mighty in Chesapeake Bay these days. They’re down to less than 1% of their historic populations due to overfishing, disease, and pollution.

A lack of oysters not only means that we are denied sweet fried goodness, but that the Chesapeake has lost the ability to clean itself. In the mid-1800s, it’s estimated that oysters filtered all the water in the Chesapeake in 3.3 days. Now there are only enough oysters to filter the water once each year. No oysters means too much phytoplankton which means hypoxia and more oyster death. And despite a $58 million attempt (a somewhat half-hearted attempt, but a lot of money nonetheless) at oyster restoration, populations have not rebounded.

Now the Army Core of Engineers and Maryland Department of Natural Resources is proposing to introduce the Suminoe oyster (Crassostrea ariakensis) to the Chesapeake. The Suminoe oyster is native to Asia, and theoretically resistant to the diseases that have decimated Atlantic oysters. The idea is that sterile (triploid) Suminoe oysters will be introduced to the Bay to filter their little patooties off, thus improving water quality and paving the way for a native oyster recovery. Unfortunately, a small percentage of sterile triploid oysters have the power to revert to fertile diploidy, meaning that the Suminoe oysters could likely establish themselves permanently in the Bay.

Non-native bivalve species do not have a particularly dignified history. Zebra mussels certainly have improved water quality in the Great Lakes, but at the cost of $5 billion a year and significant loss of native species. Atlantic oysters introduced to the West Coast brought along a whole passle of invasive species that grew on and around their shells, including tunicates and snails. And Asian clams accidentally brought to San Francisco Bay may cause selenium poisoning in the wildlife that eats them.

So the Suminoe oyster introduction could have unforseen consequences to the Chesapeake’s tattered ecology. However, this project could be an expensive boondoggle even without the potential for invasion. Suminoe oysters are not resistant to hypoxia (low oxygen). And the Chesapeake tends to go hypoxic every summer. So Maryland could spend a lot of money outplanting expensive new oysters to have them all keel over a year later.

It seems ludicrous to me to introduce a new species before getting pollution and overfishing under control. Water quality is poor because the last housing boom wrecked the last of the intact watersheds and fertilizer and chicken poop still run off right into the Bay. Hypoxia and disease are just going to keep getting worse unless the water gets better. And the Bay’s fabled watermen are fishing their way to self-destruction. Blue crabs are overfished to functional extinction – 60% of all the crabs in the Bay are removed every year, including reproducing females. And oysters are still harvested even as their populations reach historical lows.

If you care about the future of oysters in the Chesapeake, now’s the time to make your feelings known. The Proposed Environmental Impact Statement on introducing non-native Suminoe oysters is open for public comment until December 17th. Managers are going to read every single comment (as they are required to by law) and then choose their favorite plan, or as it’s termed, “preferred alternative.” Here’s the plans (“alternatives”) they are considering. NOAA’s Chesapeake Office has even more information. I’ll be telling them to stop fooling about with species introductions and to concentrate on water quality and Alternative 3 – closing the oyster fishery and compensating watermen.