Oysters

In Scotland we used to enjoy foraging; wild fungi, blaeberries, blackberries, sloes and so on. We haven't found too much here except for the oysters which cover the rocks around the inlet.
A lot of people pick and eat them straight away, which appears to have happened to these ones. I haven't tried to collect any yet, something at the back of my mind says you only eat them if there is an 'R' in the month. Or is that only in the northern hemisphere, or does it apply to pork, or......