Triploid Oysters, For the Months Without 'R's

A pretty good article on the use of triploid oysters in aquaculture here in the Bay.

Aquaculture endeavor aims to produce a more-sterile oyster

...the triploid oyster, a virtually sterile creature that grows faster and is more disease-resistant than wild or domesticated diploid oysters and, just as important, can be eaten in summer without the loss of taste and texture that afflicts bivalves tied to spawning cycles. The triploid might just put to rest the adage that oysters should be consumed only in months with an "R" in their name. Without question, the triploid increasingly is the go-to oyster of Chesapeake watermen.

Historically, oysters were not consumed months without Rs (May, June, July, August) for two reasons.  First, oysters spawn in the summer months, and are rather thin and watery as a result.  They're perfectly edible but they are not the plump oysters of fall and winter, which are accumulating the material to produce eggs (essentially all legal size oysters are females, since they change sex from male to female as they grow).  Triploid oysters are sterile from the extra chromosomes (being unable to match the chromosomes into pairs for meiosis. Hence, they don't spawn, and continue to accumulate the good stuff all summer long.  Hence edible all year long!

The second historical reason for the 'R' months rule was lack of refrigeration.  Oysters don't keep or ship too well at high temperatures, and so before refrigeration was widespread, oysters could only be held for long periods at low temperatures during cooler months (unless somebody was saving ice and snow from winter, which was done).

The months with 'R's rule has also been applied to mussels and other shellfish in various places, including the West Coast.  The reason there (refrigeration aside) is that summer months are usually when the toxic red tides bloom, and ordinary edible mussels can become deadly toxic. At least in the Bay, that has not become a problem.