You can ask in advance if the chef will cook up a fillet for you. I did that and had a GREAT dinner for the wife and myself. I took a Dorado into the kitchen, gave 1/2 to the chef for his personla use, and ate the other half. The looks from the other guestst in the dining room were priceless when the chef personally delivered a sizzling platter of dorado with lemon, butter and garlic . Tipped him $20 and the head waiter $10. Well worth it.
Should add that we got incredible service in the resort after that!