Sadly, causing occasional damage to a fish is just going to happen from time to time and there's only so much that one might do to prevent or avoid it. I remember refusing to use treble-hook baits of any kind while bass fishing (for many years) after accidentally putting a four-pound bass's eye out... when (apparently) this particular bass elected to just "slap" at my crankbait (instead of biting it) and was hooked on the outside of its head and through one of its eyes. I always practice catch and release when it comes to bass fishing. I know it seems like a relatively small thing to some, but it caused me much anxiety and even sadness every time I would think of such a magnificent predatory creature having to live out the rest of its life blinded in one eye because of me. Since that time, I've caught several others that were missing an eye... I'm guessing for the same reasons as the one I snagged. It's always a sad thing to see for sure.