Overfishing goes back 1000 years

"We are discovering that human pressure on marine life was much earlier, much larger and much more significant than previously thought," says Poul Holm, an environmental historian at Trinity College Dublin in Ireland. "We now know that there was major commercial exploitation of fisheries, doing huge damage to fish populations, back in medieval times and even before. The idea that it is only modern fishing technology that has done damage turns out to be completely wrong."
Human fishing spree goes back 1000 years

The sea has long been exploited, but not to the degree previously imagined. These are the findings being discussed at The Oceans Past II conference in Vancouver, Canada, part of the decade-long Census of Marine Life, due to be completed next year.

One particular quote I like from the NewScientist story quoted above:

…in 1153 a Moroccan geographer called al-Idris wrote that the north Atlantic Ocean contained "animals of such great size that the inhabitants of islands use the bones and vertebrae in place of wood to build houses".