Whisk together the lime juice, olive oil, mustard, ginger, garlic, cayenne pepper, and black pepper in a bowl, and pour into a resealable plastic bag. Add the salmon steaks, coat with the marinade, squeeze out excess air, and seal the bag. Marinate in the refrigerator for 1 hour.
Preheat an outdoor grill for medium heat, and lightly oil grate. Remove the salmon from marinade, and shake off excess. Discard remaining marinade.
Grill until the fish flakes easily with a fork, 5 to 10 minutes per side depending on thickness.
