“There were a hell of a lot fewer autistic kids when people (many people, at least) ate fish on Fridays.”
True.
But not just any fish. That was wild-caught fish.
Omega-3 is developed in animals when they eat grasses. This is true for fish when they eat kelp and sea grass and for land animals when they graze on grass, such as grass-fed beef.
The problem is that alot of the fish in the store is farm-raised and on those farms they fed the fish a grain-based diet. Grass-fed beef or chicken has more omega-3 than farm-raised fish.
Wild tuna and wild salmon are carnivores.