Q.Freshwater Trout & Hatches
What is a hatch and why does it matter for fly fishing?
A.
A hatch is the mass emergence of aquatic insects (mayflies, caddisflies, stoneflies) from their underwater larval stage to airborne adult form. Trout feed selectively on whatever's hatching, often ignoring other food entirely during peak emergence. "Matching the hatch" — using a fly that imitates the active insect — is the foundation of dry-fly fishing.
Hatches are temperature- and photoperiod-driven, repeating in roughly the same window each year. Sulphur, blue-winged olive, green drake, hendrickson, and various caddisflies have predictable hatch windows. Hatch calendar pages cover specific rivers and species.