Lobsters are always considered a luxury food, and it’s unlikely that you’ll eat them often. However the Marine Conservation Society advises avoiding American lobsters from Southern New England as they are a vulnerable source.
Lobsters are available both live, cooked and frozen if you know where to buy them (cooked are often the easiest to manage and the flesh can be removed from the shell with only a limited amount of expertise). Lobsters can grow to be 4.5kg/10lb, but are best eaten at about 500g-1.4kg/1lb-3lb. In general, the smaller the lobster, the more tender it will be. Coldwater lobsters from more northern seas are considered to be the finest quality.