Paleoichthyology

It’s a real word, referring to the study of fish in the past, as detailed in a recent Atlantic article:

The Medieval Practices that Reshaped Europe’s Fish

In Europe, aquatic animals have been traded at least since the days of the Roman Empire. But it was during the early Middle Ages, with the arrival of widespread Christianity, that the animals became a popular source of protein. That’s partially due to the roughly 130 days a yearwhen the faithful were exhorted not to eat meat, because fish didn’t count in that category.

At the same time, expanding agrarian populations were cutting down forests to create fields and diverting rivers to fill defensive moats around castles and towns, Hoffmann writes in one paper. From the ninth century a.d. to the 11th, the number of grain mills built along rivers in England exploded from about 200 to 5,624. Species that came into fresh water to spawn, such as salmon and sturgeon, began declining. New regulations, such as King Philip’s, were put into place to manage fish populations. A Scottish statute from 1214 required all dams to include an opening for fish and barrier nets to be lifted every Saturday, for instance. Soon highly sophisticated aquaculture ponds stocked with carp also provided regular access to fish for the landed elite.

This decline in freshwater populations coincided with a sudden, commercial-scale boom in sea fishing, which began around a.d. 1000 and is known as the “fish event horizon.” In one study, archaeologists collected cod bones in London from 95 Roman, medieval, and postmedieval sites. The number of bones jumped circa the year 1000, and isotopic sampling showed that in the following centuries, fish came from farther and farther away, indicating long-distance trade. In the southern English town of Southampton, the remains of marine species (such as cod) began to outnumber freshwater species (such as eel) by 1030.

That “fish event horizon” could have been caused by a number of forces. It came at a time of population growth, urbanism, new ship technology, and increased trade, says the archaeologist James Barrett, from the University of Cambridge. But, he adds, “I’ve argued consistently that this must also be about human impacts on freshwater and migratory fishes. The degree of vulnerability of fishes depends on how bounded the ecosystem they occupy is.”

In other words, because their habitat was smaller, freshwater fish were more likely to respond to human pressures sooner. When the reliable stocks of freshwater fish began dwindling, hungry Europeans turned to the much larger oceans. And while those populations had larger ranges, humans still had an impact.