I think we generally do our best to take care of the fish we catch. Still, there are lots of theories on how best to do it, and it can get pretty confusing.
Should we use ice or not? Should we add products to the water in the livewell? Is it better to lip the fish or hold them with two hands? I’m not a biologist, but through simple trial and error and observations over the course of my career I believe I have some ways to keep fish healthier.
It all starts with the hook set. There are some baits that fish are more prone to swallow, and others that are almost guaranteed to get the hook in the lip of the fish. There's not much we can do about it, but whenever possible early hook sets are better for the fish. If we allow a fish to choke a Carolina rig down to the gullet then set the hook, that fish is more apt to be injured. Although there’s no way to keep this from happening, just understanding that early hook sets help is a good start.
Landing the fish is when most of the damage is done. Keep the fish off the carpet of your boat at all costs. For fish that are big or tough to handle, I do my best to land them on a large sticker that I have in the center of my front deck. This sticker is plastic which is much better for the fish than carpet, especially hot, dry carpet.
When I swing a fish in the boat, I often catch the line and keep the fish from landing on the carpet. Most of the time I like to reach down and boat the fish by hand, thereby eliminating a lot of stress on the fish.
Once you have the fish in the boat, get the hook removed as fast and as non-invasively as possible. I like to hold the fish just about where the head and the body meet on the back while I remove the hook(s). I use my thumb, first and middle fingers and with a little pressure you can immobilize the fish while you hold them. You must have wet hands. As an alternative, lipping them isn't a bad way to hold them, and for bigger fish it's the only option. Then get the fish back in the water or into the livewell as quickly as you can.