What does a stream rainbow actually eat day to day?

Mostly things you never see: roughly 80–90 percent of a drift-feeding rainbow's diet is taken underwater — mayfly and stonefly nymphs, caddis larvae and pupae, midge larvae, scuds — delivered by the current as "drift," which peaks at dawn and dusk when invertebrates lose their grip or migrate. The dramatic surface rise that defines trout fishing in the popular imagination is the visible 10–20 percent. Seasonal riders join the menu: terrestrials (ants, beetles, grasshoppers) in late summer when meadow banks feed the river, eggs behind fall spawners, and minnows year-round for larger fish. The practical rule follows directly: when nothing rises, nothing is wrong — fish subsurface, because that is where the eating almost always is.

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