And why does it say to avoid Sea-Cage farmed Salmon??? Would have thought that would be a good sustainable way to eat fish...
I didn't know either, but have a read of http://goodfishbadfish.com.au/?page_id=1092
Most of the farmed fish are large, predatory species (Tuna, Kingies, Atlantic Salmon, etc). These fish need protein to grow / survive, so to supply this to the fish, they use wild caught fish (such as sardines) ground up into fish meal to feed to the caged fish.
So even though these table fish are farmed, they're being fed vast amounts of (processed) wild caught fish, which means the impact of this farming feed method is just as "bad" as if they were wild caught (so therefore not sustainable?).
That page does talk about alternate protein sources for use in the fish feed, but its an interesting aspect which I honestly had not considered before. Each slice of farmed salmon is really many, many baitfish.
But yeah, I don't know about subbing marlin with LJ or tuna with whiting.... doesn't sound right to me.