Preheat oven to 350 degrees F. Coat a 9- x 13-inch baking dish with cooking spray. In a large skillet over medium heat, melt 6 tablespoons butter. Add celery, onion, carrot, garlic, salt, and pepper and saute 5 minutes, or until vegetables are soft.
Remove from heat and stir in bread crumbs and bacon. Evenly spoon mixture onto fish fillets, roll up jelly roll-style, and place seam side down in prepared baking dish. Brush with remaining butter and sprinkle with paprika. Bake 30 to 35 minutes, or until fish flakes easily with a fork. Serve immediately.