Sea run browns feed more on small fish like bullys and whitebait. They often feed during a outgoing tide at night, the smaller baitfish move closer to the bank where the current is slower making it easier for the trout to catch them.
River browns mainly eat nymphs with the occasional terrestrial insect and the odd small fish. Due to the lower food value of the insects trout would feed for much longer.They also often feed more strongly when the water is warm, maybe due to more insects are hatching at that time.
Searunners tend to come closer to shore at night to chase smelt into the shallows to feed. Good flys to use for them are yellow rabbit and hopes silvery. Searunners feed on nymphs and drys further upstream aswell.
Resident browns do feed on smelt aswell in the lower reaches of rivers but tend to stick to mayfly and stonefly nymphs upstream