Deep hooked fish can be released.

[willcfish]

I have found if the line is cut close the fish will dissolve the hook most of the time.
https://www.youtube.com/watch?v=x6XlGPMEwao

[jessemorris]

It is usually better than pulling his guts out to get the hook out but, he may not survive still. But, some chance is better than none. I have a caught red fish with fishing line trailing from the anus. There was a jig in the fish’s stomach and the hook was nearly dissolved. The lead head would have passed eventually.