i learned today that they are fed here with heat treated herring meal.
That
the salmon enhancement program suspect the feed to contain hormones ,
because they bought some feed from a farm when running out their own
feed to
raise young  wild salmons. They observed an anormal growth spurt in a
few
week of using it.
The wild salmons eat lot of very small crustaceans and little fishs (
they
have an herring feast here in the spring) they themselves are predated
a lot
by seal, orcas, otters, eagles, bears and human . More they eat
shrimps more
they are red fleshed and .fatter( the sockeye salmon  is a delicacy)
Looking for more information.
jean-claude