Fish (or veg) Tostadas with corn and black bean salsa

• 1 tbsp extra virgin olive oil
• 300 g snapper, cut into 1inch thick strips
• 2 tsp paprika
• 1 tsp cumin
• 6 corn tortillas
• 400 g tin black beans
• 1 corn cob
• 1 large tomato, diced
• .5 red onion, finely diced
• .25 cup coriander (cilantro), finely chopped
• 1 avocado, mashed
• 1 lime, cut into wedges