In large skillet heat oil over moderate heat until hot. Add onion and cook, stirring occasionally, until golden. Add anchovies and cook, stirring, over low heat until melted. Add fennel, nuts, raisins and sardines and cook over low heat, stirring occasionally, for 5 minutes, or until heated through. In a large pot of boiling salted water cook the percatelli until al dente. Drain. Transfer to a serving bowl, add sardine mixture and bread crumbs and toss to combine.