Short answers, pulled from the story.
Thomas Aquinas requested fresh herring to regain his strength while lying on his deathbed at the monastery of Fossanova south of Rome in 1274. This specific request highlights how deeply the fish was woven into the fabric of European life, even reaching the highest echelons of religious thought.
The herring industry in Scotland reached its peak in the late 19th century when Shetland and its town Lerwick became known as the herring capital of Europe. Historical records from 1792 describe a wager where three men ate 60 red herrings with three half-gallon loaves and drank six gallons of beer, illustrating the cultural significance of the fish.
Females may deposit between 20,000 and 40,000 eggs which sink to the sea bed and stick in layers to gravel, seaweed, or stones via a mucous coating. If these egg layers become too thick, they suffer from oxygen depletion and die, entangled in a maze of mucus, requiring substantial water microturbulence provided by wave action or coastal currents to survive.
Predators of herring include seabirds, marine mammals such as dolphins, porpoises, whales, seals, and sea lions, as well as predatory fish like sharks, billfish, tuna, salmon, striped bass, cod, and halibut. Thresher sharks use their long tails to stun the shoaling fish, compacting their prey school by swimming around them and splashing the water with their tails, often in pairs or small groups.
Baltic herrings larger than 25 centimeters are eaten twice a month, while herrings smaller than 17 centimeters can be eaten freely. The contaminant levels depend on the age of the fish, which can be inferred from their size, with large Baltic herring slightly exceeding recommended limits with respect to PCB and dioxin.