Lobster Salad Rolls with Shaved Fennel and Citrus

INGREDIENTS

• 3 cups coarsely chopped cooked lobster meat (about 3 [1 1/4-pound] lobsters)
• 3 tablespoons canola mayonnaise
• 2 teaspoons chopped fresh tarragon
• 1/2 teaspoon kosher salt, divided
• 2 cups thinly sliced fennel bulb (about 1 medium)
• 1/2 teaspoon grated orange rind
• 1 tablespoon fresh orange juice
• 1 tablespoon fresh lemon juice
• 1 tablespoon rice wine vinegar
• 2 teaspoons extra-virgin olive oil
• 1/4 teaspoon freshly ground black pepper
• Cooking spray
• 6 (1 1/2-ounce) hot dog buns