Preheat oven to 220 degrees. Line a large baking tray with non stick baking paper.
Wash the clean & gutted fish. Wipe the inside & outside with a paper towel. Use poultry scissors to trip the side fins, to cut off the dorsal (at the back) and the belly fins & trim the tails to a v shape. Use a sharp knife to cut 2 slashes, about 1cm deep, in the thickest part of the flesh on both sides.
To make the stuffing, combine the pecans, breadcrumbs, mushrooms, chives, parsley, egg, parmesan, olive oil and lemon juice in a medium bowl and mix well.
Spoon the stuffing into the fish cavities, pressing in firmly. Place the fish on the lined baking paper & brush each side with olive oil.
Bake in a preheated oven for 12-15 minutes or until fish is cooked through and the flesh flakes when tested with a fork in the thickest part.