I FOUND A AMAZING STRATEGY FOR DEFEATING GASBAGS!Get a wyvern and start flying,which will force the gas bags to deflate because they will try to attack you.When they deflate from flying,they have a stunned cooldown to inflate,meaning that they can't attack!
They are believed to be part of the Tardigrada phylum, a group of extremophile microgranisims that can survive literally any environment, from extreme cold to extreme radiation, these guys are the hardiest of animals.
They have a damage resistance when inflated, so use a snow owl to freeze and deflate. After latest update, they can no longer be picked up or hit with bola. Heavily suggested to clear area of hostiles before KO. If timed right, you can keep gasbag in same area while tranqing by alternating freezing and shooting.