Dear Crabby Has All the Answers!
Dear Crabby: I was on vacation in Florida last week and saw a sign in a fish market advertising "Fresh Local Oysters" in big bold letters. I thought to myself, 'What are these people, crazy? Everybody knows shellfish is poisonous in months without an r in it.' When I asked them about it, they looked kind of embarrassed. So, are they crazy? What gives? Signed, Still Sunburned in Scranton
Dear Sunburned: To answer your first question, yes, there are crazy folks down here (and as the late, great Dixie Carter once said on Designing Women, "This is the South and we're proud of our crazy people. We don't hide them up in the attic, we bring them right down to the living room and show them off!"), but no, the folks in the fish market aren't crazy at all, because oysters and other shellfish aren't poisonous in months without r's.
Here's what gives: before refrigeration, seafood was hazardous to eat in May, June, July, and August (i.e., the hot months); you could get quite ill from badly-stored seafood and possibly even die. Makes sense, right? Question answered, right?
But it doesn't quite answer why they would be embarrassed by your query, does it?
There is, unfortunately, more to the story. Not to go into great detail about this, but the summer months are the mating season for oysters. Oysters in winter are firm and flavorful; in summer, though they can be watery, comparatively tasteless, and as they say here in South Carolina, slack. This is a polite euphemism. You see, oysters are immobile (if you were imagining two oysters rolling around in the surf like Burt Lancaster and Deborah Kerr in From Here to Eternity, I'm sorry to disappoint you), so they have to, ahem, broadcast the, ahem, fruits of their loins, and . . . oh, never mind. You don't want to know all the sordid details.
So no, oysters are not poisonous in summer. If stored properly, they are just fine. Still, if you want to enjoy them between the end of April and the beginning of September, try not to think too much about how oysters spend their summer vacation.