You touch it too much
Poking at your fish will cause its crunchy outer layer of skin, which traps delicious juices inside the fish, to fall apart as it cooks. Keep flipping to a minimum, and never use tongs. “Use one or two rubber or metal spatulas, or even a spoon, to flip it,” says Tentori. If fish is ready to be flipped, you will be able to easily slide a spatula underneath it. If you try prying it off too early, its crispy layer will stick to the pan.