I have an idea for raising fish but it requires a few implemented ideas first
Ponds - Ponds are built using various materials and would typically take a 3x3 to 5x5 plot of land. The purpose of a pond would be to raise some fish. Spawning pools along rivers and lakes could be scraped and placed in buckets of water and them placed in a filled pond. After a time the fish would be swimming about the pond.
Fish could eat a variety of foods, most obviously worms and bread crumbs. The pond would have to be tended to with new fresh water. Otherwise the fish will become diseased or die from asphyxiation.
In this manner, water could gain quality as fish gain quality. It would allow people to maintain a steady flow of water, by adding even quality 10 water, it would allow it to improve in time, and people could harvest and barrel away the pure quality water.
It would understandably take a fair amount of time to develop quality water with the tug of war required in raising fish but once it is attained it could be lucrative. Being able to raise fish and ultimately have better quality fish meat would also serve to better the game economy.
With the introduction of caviar we would also have more recipes for foods, as well as strictly low level int and psyche foods of varying qualities.