Another option is to design ships that will have the advantage against the Pirate fleet. If they are missile users add missile defense and hit them with weapons they don't have defenses for.
If that’s not an option, since its a tiny map, build a military starbase or two and load it up with all sorts of enhancers. You might have half their numbers, but with the proper assists you'll take them out with little to no loss.
If you can’t outnumber them, consider over powering them.
