How do I pick bait or lure size for trout?
Match the dominant prey, then adjust for temperature and ambition. Baseline: stream insects run tiny, so size 12–18 flies and 4–7 cm (1.5–3 in) spinners and spoons cover most rainbow and brook trout situations; lake trout eating 15–25 cm (6–10 in) cisco justify lures in that class. Cold water shrinks the target — a trout at 4 °C (39 °F) will not chase, so downsize and slow down; warm-but-legal water and fall urgency justify sizing up. The ambition adjustment is the big-fish rule from the diet ladder: a large offering filters out small fish and speaks directly to the minnow-eaters, at the price of fewer takes. If fish flash at your lure but refuse, drop one size before you change anything else — size is the variable trout care about most.
The full story
This answer is one piece of a longer lesson — setups, diagrams and the reasoning behind it.
More questions about Diet
Same topic, other species
- What do crappie eat at night versus during the day? — Crappie
- How does largemouth forage shift through the seasons? — Largemouth Bass
- Do muskie really eat ducks and muskrats? — Muskellunge (Muskie)
- What do the big jumbos eat that the small fish do not? — Yellow Perch
- What is the gorge-and-fast cycle, and how do I fish around it? — Northern Pike
- Why do smaller baits often outfish big ones for smallmouth? — Smallmouth Bass
- Do walleye eat crayfish and gobies? — Walleye