Bring large pot of water to a boil and boil pasta. Meanwhile prepare the ingredients: Coarsely chopping the mussels, sardines, capers and parsley and adding them to the bottom of a mixing bowl. Add lemon juice and olive oil and season to taste with salt and crushed red pepper.
When pasta is done, drain and shake dry and add to the bowl; toss with scallions, reserving some for garnish. Serve warm.