try this...
The pecan crusted fish recipe, it is good w/mahi mahi too..
http://2coolfishing.com/ttmbforum/showthread.php?t=61680
or try this for something quicker..
I used grouper for it, but mahi mahi would be good too (used filet w/skin on)
marinate fish w/fresh lemon juice, olive oil and seasonings for 30 minutes or so
seasonings - tony chachere, garlic powder, dry or finely chopped parsley, fresh ground pepper
Heat a little olive oil in a skillet (one that can go into the oven) on medium high heat, sear fish to slightly blackened, turn over and pour marinated juices over fish and pop into a 375 oven for about 10 - 15 minutes until flakey...don't over cook or it will be too dry.