The giant Salmonflies of the Western mountains are legendary for their proclivity to elicit consistent dry-fly action and ferocious strikes.
Kurt said it concisely. Nothing anthropomorphic there -even non-human animals show aggression and hunger. In between -during the spawning act- they are preoccupied , simply busy. I think we can understand that too.
I'll add this web page this thread as well, since their is a lot of good info on brown spawning in it:
http://canadianangling.com/hatchery-river-restoration/
I wonder. Were the Browns that were introduced to other continents and countries, inner bred as much as the Browns of N. America?