Mexican Ceviche Tacos

Name: Mexican Ceviche Tacos
Ingredients: 1 1/4 pounds very fresh (sushi-grade) fish fillets (such as tuna, hamachi, barramundi, or mahi-mahi), cut into 1/2-inch cubes; Fine sea salt; Freshly ground black pepper; 3 tablespoons fresh lime juice; 2 tablespoons fresh lemon juice; 2 teaspoons sugar; 1 cup chopped seeded tomatoes; 3/4 cup chopped red onion; 2 tablespoons sliced pickled jalapeño chiles from jar plus 1 tablespoon liquid from jar; 1 tablespoon olive oil; 1/2 large head of romaine lettuce, very thinly sliced crosswise (3 to 4 cups); 1 large avocado, peeled, pitted, diced; 3 tablespoons chopped fresh cilantro; 12 purchased crisp taco shells; Purchased salsa