It is with the help of DNA technology in combination with archaeological studies that researchers have been able to determine that herring from the Baltic Sea were caught in one place but eaten in other places. By collecting fish bones from various excavations around the Baltic Sea, the researchers can see where it was swimming when it was caught.
9th-century fish bones found in the medieval town of Truso, in present-day Poland, were probably fished in the Danish Belts, close to a hundred miles from Truso, showing that herring was an early commodity exported over long distances. Even further south in Poland, archaeologists have found herring bones coming from the western Baltic Sea.
The fish was not only for household needs
– We have sequenced the complete DNA of 40 herrings from the 8th to the 17th century, where the age has been determined based on various archaeological excavations. In the fish’s DNA, we can determine which herring stock the bones come from, among other things based on genes for the fish’s tolerance to brackish water, says Carl André, evolutionary biologist at the University of Gothenburg.
– So the fishing was not just for household needs. In the past, herring were fished when they were spawning and could be landed relatively easily with the boats and gear of the time. Ideally, you should avoid fishing for herring during the spawning period to protect the regrowth, says Carl André.
Overfishing in the 13th century
Although the fishermen of the Middle Ages lacked today’s modern trawls, fishing could be very intensive even in the past.
In the analyzed fish, there are signs that certain herring stocks in the Baltic Sea were overfished, the researchers write in the study published in the scientific journal PNAS, Proceedings National Academy of Science.
KLIPP: Despite warnings from researchers – earlier this autumn the political majority said yes to increased herring fishing in the Baltic Sea