Preheat oven broiler. Place fish on rimmed baking sheet lined with parchment paper, season with salt and freshly cracked black pepper to taste, and broil until cooked through, 6 to 7 minutes. Let cool slightly, then flake flesh into large pieces and set aside.
In bowl, whisk together yogurt, olive oil, 1 Tbsp lemon juice, curry powder, and salt.
In 4 individual salad bowls, place cooked lentils and toss with remaining lemon juice. Top with radish, cucumber, and trout pieces. Drizzle on yogurt dressing and top with arugula.
Notes
Per serving: 413 calories; 42 g protein; 18 g total fat (3 g sat. fat); 25 g total carbohydrates (6 g sugars, 9 g fiber); 271 mg sodium