Preheat oven to 375 degrees. Line a baking sheet with parchment paper.
Cut fish into ~2 inch pieces. Dip each one individually in whisked egg, then in breading (breadcrumbs mixed with harissa seasoning). Place on lined baking sheet.
Bake for 8-10 minutes (as low as 5 minutes depending on thickness of fish), or until internal temperature reaches 145 degrees F.
While fish is baking, mix together all ingredients for mango salsa.
Assemble tacos and enjoy!