You'd almost need to invent a technology to efficiently separate them from their shells, not to mention harvesting them in the first place. They glue themselve

You'd almost need to invent a technology to efficiently separate them from their shells, not to mention harvesting them in the first place. They glue themselves to their substrate quite strongly, and my experience is that rather than pull off, any attempt to grab them instead pulls them apart. Zebra mussels (and quagga) aren't huge, either... most of the ones I see are the size of a thumbnail.