It is true that in coastal areas of New England, lobster used to be very abundant and was considered “poor people’s food.” Being cheap it was an obvious choice to be fed to prisoners, and a legend developed over the years that prisoners rioted to demand that they be served lobster less often. This story claims that lobster was so plentiful and detested that it was seen as cruel and unusual punishment to serve it too frequently.
Cute story, particularly given today’s astronomical lobster prices! But alas, there is no evidence supporting it. Experts have examined colonial historical and food records and there is no mention of prisoners ever rioting or even petitioning over lobster. They surely got it now and then, but apparently not too often!