In a small bowl, whisk together the maple syrup, olive oil and mustard. Sprinkle the mixture over the salmon filet. Coat the salmon with the chopped pecans, pressing to make sure it adheres to the fish. Bake the salmon for about 20-25 minutes or until almost cooked through and the nuts are lightly browned. The rule of thumb for fish is 10 minutes per inch of thickness. If the nuts start to burn, cover the salmon with a piece of foil.