Misto Sugo

Yes, you find things like this in Italian fish markets too: a mixture of chopped and whole fish including salmon, prawns, squid, mussels, white fish, and (I expect) whatever else the fishmonger had on hand that wasn't bony. Preparation is simple; assuming you want to serve 4 you'll need:

A pound (500 g) misto sugo
A small onion, chopped
A small bunch of parsley, chopped
2-3 tablespoons each olive oil and unsalted butter
A cup tomato sauce, or to taste
Salt and pepper (or hot pepper) to taste
1/2 teaspoon oregano, preferably fresh, chopped (optional)
1 pound (400 g) spaghetti or linguine
A few fresh basil leaves, if in season

Set pasta water to boil.
Heat the oil and butter in a fairly large skillet, and when the butter has melted add the chopped herbs. Sauté, stirring, until the onion has become translucent gold, and then add the fish, first the squid and larger chunks, and then the prawns and such, and finally the mussels and such. Sauté briefly, add the tomato sauce, check seasoning, and simmer the sauce over a gentle flame while the pasta cooks. When the pasta is just shy of being done drain it, give it one shake, and upend the colander into the sauce. Turn the heat to high and cook, stirring, for about a minute. Garnish with the basil and serve at once. Grated cheese will not be necessary.

Fish Mixtures on About:
Maccheroni alla Diaz
Spaghetti allo Scoglio, Reef Spaghetti

How to Select Fresh Fish
Other Fish Recipes