Choosing fresh shellfish is easy — if it’s alive, then it is fresh. However, shellfish can also be bought cooked. Once again, as with frozen fish, I would strongly advise against buying cooked shellfish. I have heard of cases where they have not been completely cooked; not only that, but whoever cooked it probably didn’t take as much care over the court bouillon as you would, assuming, of course, that a court bouillon was used at all, which is very doubtful. More than likely, the shellfish were only cooked in plain boiling water and, therefore, their flavour must be affected.