Yes, point defense and sensors.
I always build frigates full of only PDCs, to fend off the enemy fighters.
Also, on the fighter's strategy, make sure it says "Target first: Fighters", so your fighters engage the enemy fighters first, instead of going for the Capital ships.
And build tons of fighters yourself. You don't need shipyard facilities for that.
Everytime you a planet with an orbiting moon, put the moon to work full time on fighters, which will be placed on the big planet when the moon storage its full. I even have a moon called "FighterTown".
[ April 02, 2004, 20:15: Message edited by: Yef ]