The “strike” in fly fishing is the moment when the angler sets the hook, usually by lifting the rod tip.
Lifting the rod tip is the best way to strike in dry fly fishing for trout.
But saltwater fishing, the angler usually needs to “strip strike” by ripping the line back with the hand they use to retrieve the line.
Trout anglers fishing in the salt for the first time often lift the rod tip (dubbed a “trout strike” by saltwater fly fishers) resulting in the hook failing to penetrate the more boney mouth of saltwater species.
Some times – say when you are fishing with wet flies and streamers or fishing to targets with hard boney jaws – you need to strip strike in freshwater fishing too.