I am no expert on mussels, but this is the first time I have ever heard that they are available frozen. I would be interested to know who might be serving frozen mussels.

New Zealand mussels are usually sold frozen on the half shell. I've never heard of the black ones being frozen though.

I'm no expert either, but I was told that new zealand mussels come here frozen and not fresh. Maybe I'm wrong...

If they were whole shell mussels that had been frozen they would not open when they were cooked since they would already be dead.

I took it from the posters description that he or she was referring to whole shell mussels being procured fresh not frozen. The article that you linked to appears to be describing the frozen mussels as being either half shell green mussels, or ones that have been shelled prior to being frozen.

not true. the inductor muscle is a protein that melts at a certain temperature. it just wont spring open like the very fresh variety.