Place vinegar, orange juice, honey and 1/2 cup of the stock in a pot and bring to a boil. Mix remaining stock with cornstarch, and then whisk into the pot. Bring back to boil and cook until sauce lightly thickens. Add blueberries and chives and season to taste. Reserve on low-heat until salmon is cooked.
Preheat grill to medium high heat. Brush salmon with oil. Season with salt and pepper. Grill 3-4 minutes per side, or until cooked through. Serve salmon on a pool of sauce.