Heat oven to 375°F. Cut salmon fillet into eight 1-oz pieces; dry on paper towels.
Heat 10-inch nonstick skillet over medium heat. Add spinach and mushrooms. Cook, stirring occasionally, until spinach wilts and mushrooms are tender. Place in strainer to drain, pressing out as much liquid as possible. Place spinach mixture on cutting board; finely chop. Return chopped mixture to strainer.
Separate dough into 8 triangles. For each puff, sprinkle 1 teaspoon bread crumbs on dough triangle. Place 1 piece salmon on bread crumbs; sprinkle with 1/8 teaspoon salt. Spoon 1 firmly packed tablespoon spinach mixture on top of salmon. Top with 1/4 teaspoon lemon peel. Wrap dough around salmon, sealing well so mixture is completely covered. Place on ungreased cookie sheet.
Bake 17 to 19 minutes or until golden brown. Cool 10 minutes. Serve warm.