Ikejime; an ice pick looking device into the brain, then a specialized, long wire, pushed into the spinal canal the length of the fish to stop involuntary muscle twitching, then into the ice brine. I have never done this but I'm curious. It is said to preserve the just caught taste by preventing the build up of lactic acid in the fish as it dies slowly when just tossed into a cooler.
As for smoking a jack, you can smoke almost anything and it will taste ok. Not necessarily like fish, but like the smoke off the wood and all the crap you rub on the fish. I love smoking salmon. I think I'll pass on the jacks.
Fresh water, its white perch (crappie, socalait, etc.), white bass, cat fish (not going to make a distinction and start that debate), various sunfish, spotted bass. If big blue gill had more meat and fewer bones, they'd be #1. Very sweet tasting fish. I have kept spots to eat in the past, but not anymore. Whites are just too easy and too numerous. Like keeping a few trout but releasing the reds.