I'm sure this must be a known issue, but worthy of visiting: Even when using the Large Butterfly Net or Lasso to engage, reducing the target below 20% health and stopping all damage, the animals frequently simply fail to be captured properly. I would propose giving the items a click that only lands if the target is under 20% and perma-rooting the fish underwater so that it won't end up impossible to cast on. This mechanic has never worked properly and adds massive additional timesink due to simply not working properly.
Its always had a "chance to fail" since it was introduced, I believe it or the animals were modified somewhat several years ago due to the increased in dps output to stop them getting instant killed, could be wrong though, its been a while
I've never had an issue with capture using these steps: - Click off all damage shields - Equip capture stick in primary, shield in secondary - Pull with a low damage spell (I used Flame Lick) - Leave autoattack turned off and face away from the mob so you don't riposte it to death - Cast a weak damage shield and wait for the mob to drop under 20%. Monitor carefully, add damage shields if progress is too slow, click them all off again before dropping to 15% - Stay facing away, do not change weapons, and wait. It may take 30 seconds or longer, but you should get the captured item on your cursor
