This is just horrific. I always used to look for the "sustainably caught" label when buying tinned fish, but after a while almost all the tinned fish in the shops was being described as "sustainably caught". Then as a consumer you start to get lazy because you get used to it being described in this way.
After reading your post I checked one of the tins in my mum's cupboard, and the label had a circle with an illustration vaguely resembing a dolphin with the word "safe" above it. That could mean just about anything.