DO-AHEAD TIP: If using bamboo skewers, soak them in water for 30 minutes before grilling, to prevent burning.
Preheat outdoor or indoor grill or oven broiler.
Place fish and bell pepper chunks in a shallow dish; drizzle with pesto and vinegar and toss to coat. Let stand for 5 minutes then alternately thread them onto each skewer; sprinkle evenly with salt.
Place skewers on a grilling rack (if using outdoor grill) or on a jelly-roll pan (if using broiler) coated with a little olive oil.
Grill/broil until kabobs reach desired degree of doneness, turning once.