Combine the whitefish, capers, dill and onions in a large bowl. Whisk together the mayonnaise, sour cream, lemon juice, goat cheese, paprika and some pepper in a small bowl. Gently fold the mayo mixture into the whitefish. Taste for seasoning and adjust if necessary. Serve with radishes and crackers, if desired.
The dip can be made and refrigerated for up to 3 days.