Combine the lime juice, orange juice, olive oil, jalapeño, celery, 1/4 cup of the sliced red onion, 1/4 cup of the chopped cilantro, and the salt in a blender and puree until completely smooth.
Place the fish in a bowl, add the pureed mixture, and toss well. Cover and let marinate for 20 to 25 minutes outside the refrigerator before serving, stirring from time to time. If marinating for more than 25 minutes, cover and refrigerate.
When ready to serve, add the rest of the onion and cilantro, the mango, avocado, tomatillo and cacao nibs if using. Toss well, taste for salt and add more as needed. Serve with tortilla chips (totopos) or tostadas.