In a small bowl, mix vinegar, olive oil, cilantro, garlic, cumin seed, chilies, cayenne pepper and salt to taste.
Rinse fish and pat dry. In a large, heavy zip-lock plastic bag, combine fish and 1/4 cup of the vinegar mixture; let stand, turning occasionally, for about 15 minutes.
Preheat grill.
In a large bowl, combine cabbage, onion and 1/4 cup of the vinegar mixture. Add salt to taste.
Lift fish from marinade (discard marinade) and place on a preheated, oiled grill over high heat; close lid on gas grill.
Cook fish, turning once, until barely opaque but still moist in center (about 6 to 8 minutes).
Mound cilantro-chili slaw equally on four dinner plates. Top each with a piece of the grilled fish; drizzle remaining marinade equally over fish.