Maybe 10 minutes later, the fish was upside down on the surface, and I managed to bring it close enough for Pierce to grab the leader. So, technically, it was a “caught” fish. But Pierce wanted to get control of it long enough to take a DNA swab from its cheek — a Guindon project at the Florida Fish and Wildlife Research Institute in St. Petersburg. As he gently pulled the leader closer to the boat, the fish seemed to wake up and get really angry, and with a strength I can’t even imagine, it once again dashed away, taking another 100 feet of line with it.

At this point, I had absolutely no faith that line and leader were going to hold up long enough for us to subdue this fish. But I kept pumping and reeling, and the fish rolled upside down again as I slowly brought it closer to the boat.

Just as Pierce touched the leader, the fish dived and the battle renewed.

“Don’t you ever quit?” I muttered unhappily as I sweated and reeled.

Finally, the third time was the charm; with the fish upside down and floating toward the boat, Pierce grabbed it by the jaw and rubbed a rough sponge several times across the cheek. Then he removed the hook from its jaw, and held the fish overboard so that water would flow through its gills. Amazingly, less than a minute after a 45-minute brawl in 84-degree water, the tarpon flicked its powerful tail against his grip and charged away.

Exhausted, we both shook our heads as the skiff drifted north.

Pierce put the sponge with the DNA cells into a vial and capped it, and said he’d send it off — along with other DNA samples he has collected — in the next few days. He has been sampling tarpon for about a year in Sebastian and Key West. Guindon and her staff use the DNA data like noninvasive tags; if someone catches a previously sampled fish and takes another genetic swab, scientists learn the fish’s movements between its capture and recapture.

Pierce said he wanted to help gather information about an important Florida gamefish.

“The lion’s share of my charters are tarpon,” he said. “I’ve basically made my living for 40 years on them.”

I was just very, very glad our giant silver test subject didn’t get away prematurely.