Preheat oven to 400 degrees F.
In a saute pan over high heat, melt butter. Stir in flour and cook, stirring constantly for 1 minute. Then whisk in milk, a little at a time. season with salt and pepper. Bring liquid to boil and then reduce heat to medium-low. Simmer liquid for 4 to 6 minutes. Remove from heat and stir in 1/2 cup of the cheese.
In a bowl combine the oysters, shrimp and crawfish, and season with salt and pepper. Now stir in the milk mixture, season, and mix thoroughly. Lightly grease 12 individual pie tins. Spoon mixture into each pie tin. Sprinkle each with remaining cheese. Place in oven and bake for about 8 to 10 minutes or until bubbly. Remove from oven and serve warm.