1. Combine first 9 ingredients in a small bowl; toss gently to combine. Cover and chill until ready to serve.
2. Heat a large heavy skillet over medium-high heat. Sprinkle fish with salt and pepper. Coat pan with cooking spray. Add fish to pan; cook 4 minutes on each side or until desired degree of doneness. Place 1 fillet on each of 4 plates; top each serving with about 1/4 cup relish.