When a fish takes a fly, you seldom have more than two or three seconds to hook it before it ejects the fake food. You must react quickly to make the point of the hook penetrate the fish's mouth. We call this setting the hook. Smaller and barbless hooks require less energy to hook most fish.
Larger hooks require more energy or power even for the smaller fish.
Smaller hooks also require less energy to penetrate a fish's mouth skin. Small-hook strike and set procedure 1. Angler detects fish strike by feeling it on line or by seeing it. The high tip position absorbs some of the excess energy to prevent breakoffs 3a. As the rod is lifted up and the tip rotated, allow a few inches of slack fly line to slip from your line hand.