Combine
lobster, shrimp, crab, tuna, capers, chives and parsley in a bowl and
toss together lightly with a fork. Blend sour cream, mayonnaise,
mustard, caper juice, salt and pepper and add to seafood. Toss again
lightly with a fork. Cover and chill well. Serve over wedges of avocado
set on lettuce or, if you have small avocados, fill a half for each
serving.