Whisk together yogurt, ginger, garlic, lime juice, lime zest, honey, oil, salt and pepper in a small bowl. Place salmon in a shallow glass dish and pour the marinade over it, turning the salmon to coat on all sides. Cover and marinate in the refrigerator for 20 to 30 minutes, turning once or twice.
Meanwhile, prepare a charcoal fire or preheat a gas grill. (Do not use a grill pan—salmon will stick.)
Oil the grill rack (see tip). Place the salmon, skin-side up, on the grill. Cook for 5 minutes. Using 2 metal spatulas, carefully turn the salmon pieces over and cook just until opaque in the center, 4 to 6 minutes longer. Remove the salmon from the grill. Slip off the skin.
Toss Watercress & Pickled Ginger Salad with dressing and divide among 4 plates. Top with a piece of grilled salmon. Garnish with lime wedges. Serve immediately.
Fish on foil: Fish that flakes easily requires a delicate touch to flip on the grill. If you want to skip turning it over when grilling, measure a piece of foil large enough to hold the fish and coat it with cooking spray. Grill the fish on the foil (without turning) until it flakes easily and reaches an internal temperature of 145°F.