Cut the mahimahi into 16 equal slices, 2 to 3 oz/57 to 85 g each, and season with salt as needed.
Gently combine the vegetable oil, lime juice, chili powder, cumin, coriander, and garlic with the fish. Allow the fish to marinate for about 30 minutes.
Grill the fish over high heat until well marked and cooked through, about 1 minute on each side.