1.Tightly wrap each piece of fish, separately, in plastic wrap; freeze about 1 hour or until slightly firm.
2.Unwrap each piece of fish, slice as thinly as possible; arrange slices on separate serving platters. Drizzle tuna with lime juice; drizzle kingfish and salmon with lemon juice. Cover; refrigerate 1 hour.
3.Meanwhile, combine ginger and sauce in small jug; stand while fish is under refrigeration. Finely chop enough fennel leaves to make 1 level tablespoon; discard remaining leaves. Finely chop fennel bulb.
4.Drain excess juice from platters. To serve, divide fish among serving plates: drizzle tuna with strained sauce mixture; sprinkle kingfish with chopped fennel, leaves and half of the oil; sprinkle salmon with capers, onion, dill and remaining oil.