Cook pasta in boiling water according to pack instructions, drain.
Heat 1 Tbsp olive oil in a frying pan over medium-low heat, add the fennel and cook for 3-4 minutes, stirring occasionally until softened.
Add capers and the zest and juice from the lemon half. Flake the smoked trout and add to the pan. Add most of the parsley to the pan and the fronds from the fennel. Stir to combine, heat through and season to taste.
Gently toss the trout mixture through the pasta and sprinkle with remaining parsley.