Rinse the perch with cold water and pat dry. Season with pepper inside and out and brush with the lemon juice. Rinse the herbs, shake dry and place in the abdominal cavity of the fish. Preheat the oven to 210°C (approximately 400°F).
Mix the egg whites and salt lightly until a moldable mixture is formed, adding some water, if necessary. Place about half the salt mixture on a baking sheet and spread to about the size of the fish, then top with the prepared perch and cover with the remaining salt mixture. With moistened hands, press the salt mixture slightly to adhere to the fish body.
Bake the salt-crusted perch for about 30 minutes in the preheated oven. Carefully tap and remove the salt crust. Remove the fish skin and lift the fish meat from the bones. Serve with side dishes and sauce to taste (such as boiled potatoes and white wine sauce).