As old as a human has to be to be a human.
many; carp (most course fish) rainbow trout atlantic salmon taliapia sea bream sea bass pengasius (river cobbler) and many many more
Ocean fish..There are not that many farm raised species.
Depending upon the species of fish being farmed and the expertise and equipment being used by the fish farmers, some species are spawned and fertilised naturally and others have their ova and sperm...