The best way to tell “fresh” among live lobsters is to look for the liveliest. They get lethargic as they go along. In fact, lobsters that are held in tanks for a long time after they’re caught may move so little that they have moss growing on their shells. Do not accept a mossy lobster. Be sure the antennae of all — or most of — the lobsters in the tank are long and pointed. Lobsters are cannibals and will eat whatever parts of their companions they can get a hold of, so the more chewed they look, the longer they’ve been together. It’s also important to choose a market with a big turnover: the more they sell, the likelier it is that the ones you see have come in recently.
As you know, no market lobster can compare with one that’s straight from the wharf. If you have roadside peddlers near you who appear on a regular basis, it’s worth shopping for one who buys right off the boat.