Fish Chowder a la Arizona

2 potatoes, peeled and diced
1 onion, diced
1 (6 1/2 ounce) can tuna, drained
1 (6 1/2 ounce) can minced clams, with juice
1 (4 1/4 ounce) can shrimp, with juice
1 (16 1/2 ounce) can creamed corn
2 tablespoons butter
1 (16 ounce) can evaporated milk or 2 cups fresh milk
1/2 teaspoon white pepper
1/4 teaspoon nutmeg

Saut