Oysters and the “R” month rule of thumb- a moment of science

Storm Team 2

After a summer break, shellfish season is back open again! But why is that break June through September necessary?

There’s two main reasons for that. One is for human health concerns and the other is for ecological concerns with the biology of the oyster. Human health- there’s bacteria in the water that proliferates during the warmer months and it can also reside in the oysters.

Ben Dyer, South Carolina Department of Natural Resources

This is where that oft-repeated rule of thumb of “only eating oysters in months that have the letter r in them comes from.”

This rule doesn’t hold as much truth today.

Shellfish is shipped from cooler climates during those warmer months, advanced refrigeration keeps food fresh longer, and shellfish is farmed commercially. Even locally, wild shellfish is safer now as popular fishing spots are checked regularly by DHEC.

The Department of Health and Environmental Control shellfish sanitation program monitors water quality monthly at over 450 stations in South Carolina to make sure that recreational shellfishing sites meet health standards. These areas still may be closed temporarily, even during a shellfish season month with the letter R, as a result of a pollution event such as a tropical system increasing bacteria concentrations to unsafe levels due to runoff. 

But health and human safety is only one side of the coin when it comes to the summer hiatus there’s a biological reason too. Here’s Ben Dyer again,

“in the summer months when the water gets warmer, oysters start to spawn. They release larvae, or baby oysters, into the water. Those will settle out and land on other oysters or other hard substrates and grow new oysters. While that’s going on in the summer months we really don’t want people out there harvesting more of the substrate that new oysters could attach to.”

This is also why oyster recycling programs are so important- which I’ll focus on in another Moment of Science in the near future. Until then, now that the season has begun, maybe you’d want to grab your own oysters for dinner- first you’ll want to purchase a saltwater fishing license- available from SCDNR’s website. On that site you can see a map of which areas you can gather shellfish in the Lowcountry. Those maps also include areas to avoid based on DHEC’s monitoring as bacteria levels may be high. In the end, it’s a joint effort between SCDNR and DHEC to make sure that the shellfish we love to enjoy here in the Lowcountry is both sustainable and safe. 

Storm Team 2 Meteorologist David Dickson

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