This is Italia Coppola's father's dish, made in Naples using seafood from the Mediterranean.
When Italia cooked mussels, she likely had to trim their long seaweed beards and scrub off, if possible, the barnacles who had attached themselves to the shells. Advances in shellfish cultivation has changed everything and made it much easier for home cooks to both get good mussels and prepare them.
This classic Neapolitan fish stew has about as many versions of cooks as there are in Napoli. Italia's version includes a bounty of seafood and you do not need to use all of it; just use what you like and what is freshest wherever you are.