This year, Idaho Fish and Game is stocking 1.6 million catchable rainbow trout between 10 and 12 inches, which are stocked strictly for anglers to catch.
Idaho rainbows are typically stocked where they are easily accessible to anglers and there’s high probability they will get caught.
The agency stocks rainbow trout year round, but expands its operations as more waters open in March and become suitable for trout. Typically, ponds are the first places, followed by small lakes and reservoirs, then larger reservoirs and streams.
Steelhead are also available in the spring, and Chinook salmon start arriving in Idaho in April. At some lower elevations, warmwater fishing gets started in March and typically improves into spring.
Idaho Spring Fishing Tips
Watch the weather: Fishing is typically better when temperatures are warming and the barometer is stable. A temperature drop or a storm typically slows fishing.
Take it slow: Fish can be sluggish in cold water. Air temperature warms much faster than water, so even on a warm, spring day, the water is probably chilly. Bait is a good option, and if you’re using lures or flies, a slow retrieve usually works better.
Don’t overlook warmwater fish: They become active sooner than you might think, but expect subtle strikes, and the fish to be in different places than where you found them last summer. Bass fishing can be good. Catch rates tend to be low, but the biggest fish are often the first to become active.
Smaller, shallower waters typically warm faster than larger bodies of water. Ponds and small reservoirs are good options. Same goes for shallow coves, bays and flats in larger lakes and reservoirs.
Check Fish and Game stocking reports at http://fishandgame.idaho.gov/public/fish/stocking/ for good places to catch rainbow trout and other fish.
Watch for hatches: Fly anglers can find good early season bug hatches, which are typically chironomids (midges) or baetis (blue-wing olives). There are usually trout feeding on them.
Spring is a good time of year to explore local ponds and reservoirs, especially if unfavorable weather or water conditions could impact longer trips.
source: Idaho Fish and Game