Catfish have very sharp bones in their top and side fins that they can literally lock in place, for small ones keep the belly to your palm and hold under and over the locked spines for a sure grip, with big ones hold like a little kid with both hands wrapped around them under the spines belly to belly (don't be afraid to give it a kiss while your there) With Northern Pike and Muskie watch out for the teeth and aggressive nature, long handled needle nose pliers do the trick for them (and a small club if keeping) I lay them down and gently kneel on them to keep from flopping and biting when removing the hook, hold them across the back of the head using the gill openings as a handle and support the weight with the other hand if your releasing them, same goes to other fish with teeth.