It looks like a joke today, but it was quite helpful response back then. When shortages started to be massive, people from towns tried to find merchandise in cities, so they asked often «— Do you have a meat? — No, we don't. — You don't have a meat because you are selling something else or because of shortage? — We are selling fish. — Where I can find a meat shop? — Down the street, but they have no meat today too». (Sorry, if my English is incorrect).

Compare this dialogue to short but informative reply in the «joke» above.

Later, these responses are replaced with stickers like "No MEAT today" (it's meat shop, but we out of meat today, check us next morning) or "NO meat" (nobody saw a meat for at least two months, so don't ask us when it will be).

Maybe you understand this joke now:

Developed communism. «From each according to his ability, to each according to his needs.» Sticker at the shop: «NO need in the meat today, comrades».