Heat 90ml of oil in a large frying pan and fry fennel, onions, fennel seeds, and chillies for 20 minutes until soft.
Stir in half the sardines, all raisins, and pine nuts, then cook for 10 minutes until sardines disintegrate.
Add wine and 175ml water, simmer until reduced by half, then cook until thickened and season with salt and pepper.
Lay remaining sardine fillets skin-side up on the sauce and drizzle with 30ml olive oil.
Cover the pan and cook over low heat for 10 minutes until the fillets are cooked through.
Boil linguine in salted water until al dente, then drain well.
Toss the pasta with the sauce, whole fillets, and remaining 30ml olive oil.
Serve with lemon juice, zest, and reserved fennel fronds.