Preheat the oven and a large flat oven tray to 220°C fan forced. Place the sweet potato into a bowl. Drizzle over 2 tablespoons oil and season with salt and pepper. Toss well to coat. Spread the chips in a single layer onto the hot tray. Roast for 20-25 minutes, turning once, until tender and golden.
For the salsa, whisk oil, lemon juice, sugar and salt and pepper in a medium bowl until well combined. Cut, peel and dice the mango, add to the dressing with the tomatoes, green onions, jalapeño and coriander. Toss gently to coat.
Ten minutes before the chips are ready, season the fish with salt and pepper. Heat half the remaining oil in a frying pan over a medium high heat. Add two pieces fish, skin side down. Cook for 1-2 minutes until golden, turn fish over and cook for 1 minute. Transfer to a baking tray, skin side up. Repeat with remaining fish. Place the fish into the oven, under the sweet potato and cook for 6-8 minutes or until cooked through.