To claim that fishing on a commercial scale for any wild species of marine animal is sustainable is at best optimistic and at worse misleading.
There is NO accurate way of measuring the stock of a commercial species and in most cases scientific data provided by Governments will err on the side of optimism.
The links below provide three different sources of information about the 'sustainability' of Atlantic swordfish. If you take time to absorb the information you will realise that, whilst well meaning, it is innacurate, confusing, and smacks of guesswork.
Sustainability is the current buzzword, but to truly ensure that a wild species will survive, refuse to eat it.