[Powerful Catch Spawn Rules]

While fishing, certain kinds of fish and rare subspecies will appear as powerful catches.

[Powerful Catch Battle Tutorial]

Powerful Catches have a red Excitement Gauge. Reel the powerful catch to deplete its Excitement.
Once Excitement is depleted, the powerful catch will enter a Weakened state for 4s.
While the powerful catch is Weakened, repeatedly press to eliminate a large amount of stamina.