Can you get mercury poisoning from too much sushi?

We posed this to Karen Kidd from the University of New Brunswick:

Mercury has been very well studied and we know a lot about its effects on human health. There's some great advice available on the web in terms of the types of fish that are safer to eat. For example, we know that fresh tuna has a lot more mercury in it than canned tuna, swordfish is another one that's high in mercury. We know that bigger, older fish are higher in mercury, so what I would recommend that everyone do, is take a look at that advice on the web and choose fish that we know are lower in mercury.

The Food Standards Agency have some advice online here.