The reality is that the Gulf only supplies a very small percentage of US seafood – well below 5%, maybe 2%-3% if memory serves. And maybe 6% of all US shrimp.
Most of the shrimp – even in New Orleans – comes from Asia. A lot of the fish – and 100% of catfish – come from farms that aren’t actually in the Gulf itself (although in the region). And a lot of fish come from Asian fish farms as well.
I don’t know about crabs and oysters… I think most of New Orleans’ supply of these is local, so I’d think a decent amount comes from the Gulf itself.
My point is that if you sit down at Galatoire’s and order a seafood platter (which I suggest, by the way), a relatively small percentage of what shows up on your plate will actually be from the Gulf of Mexico.