Why does the system permit sea fish but ban tilapia and mullet — all of which are fish?
Sea fish vs farm-raised fish
What the system says
The system distinguishes by what the fish ate during its life: sea fish eat smaller fish and natural marine creatures, while farm-raised fish are fed industrial pellets that may contain additives and hormones. Hence tilapia and mullet are classified among the "industrial" foods.
What science says
Scientifically: wild fish generally have more omega-3 because they eat omega-rich smaller fish, but regulated farm-raised fish remain a good and economical protein source. It's a quality gradient, not a binary. More important than wild/farm is avoiding high-mercury fish (large tuna, swordfish).
Smaller sea fish (sardines, mackerel, anchovies) are the optimal choice nutritionally and economically. Farm-raised fish from reputable sources are not "dangerous."