Preheat oven to 350 degrees.
Par-boil northern fillets wrapped in cheesecloth for about 5 minutes.
Lie fillets in large baking dish. Cover with sliced carrots and then onions.
Mix sour cream, celery soup and bread crumbs in separate bowl and pour over fish, carrots and onions.
Sprinkle with paprika and bake for 35-45 minutes or until all liquid is bubbling through fish.