This is what researchers at the University of Gothenburg, among others, who have studied old fish bones from archaeological excavations in countries around the Baltic Sea, report Science Radio.
Through DNA analyzes of archaeological finds of fish bones, the researchers have seen that the genetic variation of the herring has been lower during certain periods, which could be a sign of overfishing.
Since the 1970s, however, it is estimated that herring have declined by 80 percent in the Baltic Sea, largely due to fishing.