Lent
Lent is a six-week period of fasting that falls between Ash Wednesday and Easter Day.
The period of Lent marks the 40 days Jesus spent in the desert being tempted by Satan (see Luke 4, 1-13; Matthew 4, 1-11; Mark 1, 12-13), and it culminates in commemoration of Jesus' crucifiction, death and resurrection.
Lent is a time for prayer, fasting and almsgiving. Prayers tend to ask for the forgiveness of sins, that God's grace might save folk from themselves.
The Lenten fast forbids eating before nones (around 3pm in spring). The fast also forbids eating meat, eggs or dairy products (butter, cheese and milk). Water (or watered ale or wine) is permitted before nones. The nones meal is the only one permitted during the days of Lent, though some communities also allow a snack before bed-time. Exceptions to the fast are made for the elderly, young, sick and very poor.
Fish was permitted, and was an important addition to the bread and water fast diet. Manors and religious houses with fishponds others with riverine fishing rights might dine on freshwater fish such as trout, salmon and eels. Coastal areas had a good supply of coldwater fish, including cod, haddock, and flatfishes. Some areas had oyster beds.
Preserved cod or haddock was expensive. Everyone else might buy salted, smoked or brined herring, a small, common forage fish that is easy to catch. Herring migrate, and are usally caught off English and Scottish shores in great numbers in autumn. The fish is oily and preserves well. King Herring ruled the Lenten period, not matter how much folk complained of the monotony of a diet of salted herring - and they certainly complained of that. Easter eggs might be derived from a pagan tradition, but they are certainly a sign of relief that the fast is over.
Frugal householders would buy salted herring or other preserved fish in autumn, when they are cheap and plentiful, rather than waiting for the start of Lent. Even more frugal households, and larger religious houses, might buy fish prepared for preserving, but do the preservation themselves - one Margaret Cressey in her will made arrangements for five cartloads of alder wood to be delivered to the nuns of Godstow, Oxfordshire, every year in October so they might dry their herring.1
Those who owned fishponds would take care to stock them in September to ensure a good supply in Lent. Durting the fast weeks, the owner of a pond might post a guard on it to prevent theft.
It's also because of this the Mardi Gras came about. The puffin was classed mistakenly as a 'fish' during this period at one stage as it could dive for food in water, so could be ate.