Archaeologists and scientists have revealed that 1,000 years ago cod was traded extraordinary distances across Europe, from the Norwegian Arctic to England and the Baltic.

The research may force yet another revision of the image of the Vikings, from longship ram-raiders, to mainly traders and colonising farmers, to the fishmongers of Europe. Vikings in York were eating cod caught off the Norwegian coast.

The research, reported in this month's Journal of Archaeological Science, also shows the 1,000-year-old origins of the modern problem of declining fish stocks, as fishing grounds had to supply far more than a local market. The emergence of commercial fishing "may represent the point at which people started to have an impact on marine ecoystems," said James Barrett, of Cambridge University's archaeology department.