Preheat oven to 400°.
Combine the first 10 ingredients in a large bowl; gently fold in salmon.
Place 1 phyllo sheet on a large cutting board or work surface (cover remaining phyllo dough with a damp towel to prevent drying); lightly coat with cooking spray. Sprinkle about 1 1/2 teaspoons breadcrumbs evenly over the phyllo. Repeat layers with the remaining phyllo, cooking spray, and breadcrumbs, ending with phyllo.
Spoon salmon mixture along 1 long edge of phyllo, leaving a 2-inch border. Fold over the short edges of phyllo to cover 2 inches of salmon mixture on each end. Starting at long edge, roll up jelly-roll fashion.
Place strudel, seam side down, on a baking sheet coated with cooking spray. Brush butter over top of strudel. Cut 4 diagonal slits into top of strudel using a serrated knife. Bake at 400° for 25 minutes or until golden. Let stand 5 minutes. Cut strudel into 4 portions using a serrated knife.