Place the fish in a stainless-steel or other nonreactive bowl. Add the lime juice and gently stir to coat the fish. Cover the bowl with plastic wrap and refrigerate until the fish is opaque, about 3 hours.
In a small bowl, stir together the tomato juice, olive oil, and oregano. Season to taste with salt, cover, and refrigerate.
Just before serving, drain the fish and stir in the onion, tomatoes, chiles, olives, cilantro, and the tomato juice mixture. Taste for seasoning and add sugar and salt as needed. Add the avocado and toss gently. Serve with tortilla chips or crackers.
