Peruvian Marinated Shrimp (Seviche de Camarones)

1 to 1 1/2 pounds cooked shrimp, peeled and deveined
1/2 cup each lemon juice, lime juice, orange juice
1 small onion, finely chopped
1 scallion (spring onion) green and white parts, finely chopped
1 tomato, peeled, seeded, and chopped
1/4 cup chopped cilantro or parsley
Finely chopped red or green hot chile pepper, to taste
Salt and freshly-ground pepper, to taste
2 to 3 avocados, halved and pitted (optional)

Combine all the ingredients except the avocados in a glass or ceramic bowl and stir to combine thoroughly. Chill for at least 1 hour before serving.

Serve mounded on the avocado halves, or on a bed of lettuce.

Serves 4 to 6.