7. Farm-raised fish had its birth during the medieval period
During the medieval period the very wealthy, those living in castles or on landed estates, often left the fish swimming in the streams and lakes nearby for the use of their tenants and wandering vagrants. They used ponds, sometimes building them, on their estates to raise fish of their own, sometimes stocking fish not indigenous to local waters. Though by no means the fish farms which emerged as part of the commercial food industry in the twentieth century, they were early versions of the same concept. Fresh fish was thus always available for their tables, and salted or dried fish was available for trade, or even sale to the peasantry.
Eel was also widely popular, as it is today for those with a taste for it, and was eaten fresh, pickled, or dried. Eel was so common in the waters of Europe that fishing nets intended for other fish often became clogged with the creatures. Since eel was so common, it came to be regarded as being for the common people. Well into the twentieth-century eel, especially in England, was regarded as a food for the urban poor, and eels were harvested in the Thames River in the center of London. They were also popular in the German provinces, as well as in France and the Scandinavian countries.