1. Soak plank in water 1 hour; drain.
2. Preheat grill to medium heat.
3. Combine syrup and mustard; stir well, and divide between 2 small bowls.
4. Place plank on grill rack; grill 10 minutes or until lightly charred. Turn plank over; place fish, skin side down, on charred side. Sprinkle fish with salt and pepper; brush with half of syrup mixture.
5. Cover and grill 35 minutes or until desired degree of doneness. Remove from grill; spread remaining syrup mixture over fish. Cut fillet into 4 equal portions.