Heat grill to medium high. Remove skin from salmon. In a small bowl, combine chili powder, oregano, salt and pepper. Generously dust fillets with spice mixture. Set aside. Drain beans of almost all liquid, keeping about 2 tablespoons of the liquid to cook beans in. Heat beans in saucepan for about 3-4 minutes until they bubble. Using a spatula, smash beans until they thicken. Season to taste with salt and pepper. Remove and set aside. Shuck the corn, brush with canola oil and grill for a total of 5-7 minutes, turning to cook all sides evenly. Remove from heat and use a knife or corn stripper to remover corn from cob. Set aside. In a small bowl, mix avocado, mango, red onion, red pepper, cilantro jalapeño and lime juice. Set aside. Cook salmon. Heat 1/2 the canola oil large non-stick pan over high. Sear salmon for 30 seconds and turn to medium low. Cook about 4 minutes. Turn fillets and cook about 3 minutes more, or until still a little pink in the center. Heat remaining oil in a medium sauté pan over medium-high heat. Fry tortillas, one at a time until golden and crispy. Remove from heat and place on a paper towel. Layer the tostadas. Spread beans on fried tortillas, then sprinkle grilled corn over the beans. Add romaine, then salmon. Top with the mango avocado salsa and serve.