Fish was an essential element in the medieval diet, especially as the Church forbade the eating of meat during the six weeks of Lent, on Fridays and Saturdays throughout the year, and on important festivals.
Large numbers of fresh-water and coastal fisheries are described in Domesday Book, though eccentricities in their distribution reveal that not all have been recorded. In some circuits few fisheries are recorded, and in some counties - Cornwall, Leicester, Wiltshire - none at all. Renders were often very substantial, but frequently commuted for money payments.
Among freshwater fish, eels were the most common and occur in the greatest numbers, in many cases in excess of 10,000 from single manors. Salmon are recorded fairly often in western districts, and one manor in Surrey rendered 1,000 lampreys (SUR 8,14).
Herrings - 'the potato of the middle ages' - were far and away the most common salt-water variety, renders sometimes being in tens of thousands. Sandwich, for instance, paid 40,000 herring; Southease, 38,500. On two occasions, the render of a porpoise is recorded, perhaps for its exotic rather than its nutritional appeal: one of the two manors paid '20s, an ounce of gold, and a porpoise' (KEN 4,2), the other commuted its obligation for £4 (SUS 7,1).
For the importance of fish, see Medieval fish, fisheries, and fishponds in England, edited by Michael A. Aston (1988); and Christopher C. Dyer, Everyday life in medieval England (2000).
See also fishponds.