Ocean City toggin

Just watched a 2010 video made by Capt. Monty. May have answered my own questions in the process. Assume the ripping procedure is to validate number of previously caught fish which survive being released. I'm assuming it's a technique to prove or disprove theories about the effect releasing fish has at various depths on mortality rates. Initially I was wondering why not just tag the fish when caught the first time. My guess is ripping the fish's dorsal fin first before tagging ensures it's not double counted each time recovered. That would be my guess. Kudos to the Captain for his efforts, seems like a real class act and operation and someone who actually tries doing something for the health of the fishery as opposed to simply talking about it.