It's too easy to catch great tasting fish in the ocean. I'm sure someone has a method for cleaning tarpon as well, but why?
I've eaten Tarpon balls (not the organ, but a method of cooking, fried chunks of meat) in Costa Rica. They were made from Tarpon that died from being line wrapped, or hit by sharks. They were actually quite good.
As far as Jack Crevalle goes, well - maybe. If I was starving, adrift in a lifeboat. Even THEN, Maybe, just Maybe! - UGH. NASTY!