Heat 2 tablespoons olive oil in a grill pan or skillet over medium-high heat. Season arctic char with kosher salt and black pepper. Cook fillets on grill pan skin side up until lightly browned, 3 to 4 minutes. Flip fillets and continue to cook until fish flakes easily with a fork, 3 to 4 minutes more. Pour lemon juice over fish; remove from heat.
Divide salad greens over two plates and arrange mango, strawberries, and pecans on top; season with salt and black pepper. Carefully place an arctic char fillet on each portion and drizzle pan juices and remaining 2 teaspoon olive oil over salads.
