Chesapeake Oysters a Tough Nut to Crack

Restoring wild oyster population proving a challenge around Chesapeake Bay

Out on the Potomac River, oysters had a particularly rough year in 2018. Plans to build a new sanctuary were tabled due to heavy rains throughout the year that lowered the salinity of the river—something oysters don’t like. Even at the mouth of the Potomac, where the normal salinity range in the winter is about 15 to 20 parts per thousand, it has dropped to about 7 ppt. That’s devastating for the bivalves.

Oysters don't like a salinity of 7, but they'll live, and grow, if slowly. Below about 3 is lethal, though. Those low salinities got pushed a long way down the Potomac, as well as the mainstem Bay this year.

Martin Gary heads the Potomac River Fisheries Commission, which regulates all recreational and commercial fishing, crabbing, oystering and clamming in the main stem of the Potomac River for Maryland and Virginia. He said a majority of oysters died in one sanctuary above the U.S. 301 bridge, an area where they normally tolerate some heavy rains. Even Special Management Areas planted with wild baby oysters and harvested on a rotational basis had “extremely high levels of mortality” and showed no signs of reproduction.

And so far this year, the precipitation hasn’t let up.

“It’s not like we’re catching a break,” said Gary, who isn’t sure conditions will change enough to be able to plant oyster seed later in the year. “Unless we go into a full-out drought, we’re not going to have conditions conducive to planting.”

Comparisons to the amount of rainfall in 2018 are being made to Hurricane Agnes in 1972, which contributed to a smothering dead zone the following year that devastated the remaining wild oyster population in the Potomac.

“The difference,” Gary said, “is that Agnes came in one fell swoop and this has been staggered throughout the year, so it’s almost worse. Late 1972, the salinities came back up. They’ve not come up in the Potomac.”

To add insult to injury, once the government shut down, so did access to data from NOAA buoys, including water salinity information, so he’s unable to keep an eye on it.

I don't see why they shut off data from the buoys, except as spite. They report autonomously, and are posted on the web without human intervention. Unless the buoy choose that moment to die, that is.

We'll see how much damage last year's rains did. All over the bay, salinities were well below normal, and that will affect a number of things.

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