I have a 12v rapala that clips to the boat battery. I mostly use it for catfish but have used it on bass and crappie. For catfish, I skin the fish first, then filet both sides off and trim the ribs out. For bass and crappie, I take both sides all the way off and then hold the tail end down with a fork and use a regular straight fillet knife to take off the skin and trim out the ribs. The electric knife is so much faster cutting through the ribs!
My electric knife has been going strong for about 6 years, but has developed a quirk. When it is connected to the battery, it is on. The on/off switch doesn't do anything. May be time for a new knife, think I will take it apart first and see if I can figure something out. I am fairly sure it happened after getting submerged.
You can find the kitchen electric knives for next to nothing at thrift stores like Goodwill if you want to try one. I think I saw some for about $2.