Mix the strained fish stock, the vegetable stock, and the pea soup in a saucepan and stir well. Season with salt and peppercorns. Simmer for 15 minutes, and before serving add pieces of cooked fish, cooked roe, and the vinegar. When the soup is poured into the tureen add the sour cream and thin strips of lemon peel. Serve with croûtons of fried bread.