Place fillets in a 13-in. x 9-in. baking dish coated with cooking spray; sprinkle with 1/2 teaspoon salt and pepper. In a saucepan, combine the V8 juice, celery, onion, green pepper, lemon juice, sugar and remaining salt; bring to a boil. Cook over medium-low heat for 5-6 minutes or until vegetables are tender. Pour over fish; dot with butter.
Bake, uncovered, at 350° for 10-15 minutes or until fish flakes easily with a fork. Serve with rice if desired.