In Medieval Europe, it was also typical for monasteries and castles (small, partly self-sufficient communities) to have a fish pond.
[1] Those with access to fish ponds had a controlled source of food, not unlike pastures for cattle and sheep, for use on days when it was not permitted to eat meat.
They provide a source of food and income from the sale of fish for small farmers and can also supply irrigation needs and water for livestock.
[2] The ecosystem and production services offered by carp farming in fish ponds have immense societal and economic advantages.
For example, per production cycle, common carp aquaculture in the whole Central and Eastern Europe fishponds offer at least 579 million € worth of services, some of which are realized while a larger part is intangible.