The best way to find out if a pirate xerj fleet has scourge with it, since they do not show up in fleet makeup, would be to send one weak small craft at it, like a broodling or fighter or coursair. You will lose a point and the ship but you will also get a accurate idea of whats in the xerj pirate fleet and if there are scourge attached to it. Better to lose a cheep ship, then part of your attack fleet because the pirate fleet was packing 100+ scourge and you hit it blind.