We suffocate them to kill them when we pull them from the sea. That's quite mean. Few people would advocate the humanity of killing a cow in the same way.

Fair enough. How much more would it cost / how much more would one have to pay for humanely slaughtered tuna and salmon, I wonder? Would there be a market? After all, we have certified-organic, fair trade, halal and kosher....

Just to call out - halal and kosher are _less_ humane than simply killing an animal in the usual industrial way

Or freeze them live into a block of ice.

Are you aware of how cows are actually killed?

I am. It's not very nice. Arguably nicer than suffocating though.