Steps
1. Preheat grill to medium-high heat.
2. In a small bowl, combine soy sauce, fish sauce, grated ginger, garlic powder, and sugar.
3. Rub the mackerel fillet with the marinade, and let it sit for 10 minutes.
4. Heat a large cast iron skillet or grill pan over medium-high heat with the oil.
5. Grill the mackerel on each side for 3-4 minutes, or until the skin is crispy.
6. Serve warm, either as is or with a side of rice.