1.Blend or process ginger, garlic, coriander root and stem mixture, chilli, spices, juice, coconut and oils until chopped finely.
2.Score fish three times both sides through thickest part of flesh; place fish in large shallow dish. Fill cavity of fish with lemon slices. Rub coconut mixture all over fish; season. Cover; refrigerate 1 hour.
3.Heat covered barbecue. Transfer fish to oiled fish grill and cook covered using indirect heat for about 45 minutes or until cooked.
4.Serve fish with lemon wedges and fresh coriander leaves.