In looking at the title of the original post "Your longest fish fight...", it offers two interpretations. As most of the respondents have assumed, this could well mean the longest amount of time (minutes) for which you fought a fish. For me, I am not sure. I have fought yellowfin and bluefin tuna off the Virginia coast for 45 to 60 mins with stand-up tackle while fishing on friend's boats.
In 2003, I hooked a 170-lb tarpon near Boca Grande. This was day 2 of our fishing with that guide. He had instructed the mate at the end of day 1 to respool the reel with fresh line. The mate was careless and bypassed the first (largest) guide on the 7' heavy spinning rod. I ended up fighting that huge fish with only the outer half of the rod. After nearly an hour, I had a big blister on my hand, and could not get the fish all the way in. It would come to the surface and gulp air to reoxygenate itself, then blast out again. Eventually I got it close enough to touch the leader before the fish broke loose.
When fighting a large fish from a kayak, I am concentrating on doing things right and don't pay much attention to the elapsed time as the adrenaline flows. In 2019, I caught a 100-lb tarpon in Biscayne Bay. That fish pulled me half a mile and made several jumps before I got it in. The fight could have been 20, 30, or 60 mins -- I don't really know.
Last April, I was pedaling a kayak two miles out in the ocean off of Boynton Beach when I hooked a sailfish. The guide had set the drag loose and did not want me loosening it. That was a long and physically tiring fight. We estimated the sailfish at 80 lbs.
Having given those examples, I go back to the title and realize that it could equally well be interpreted as how long (in inches) was the largest fish you ever fought. Again, I don't know for sure. The tarpon described above was estimated at 5'8", the sailfish at 6'6", and my largest lemon shark at about 5'. When fishing in a kayak, it is not easy or prudent to bring such large fish into the kayak to get an accurate measurement. I rely on the guide's estimate of length.
On that same trip, I hooked a spinner shark that was probably more than 6' long. It tore off at least 75 yards in a few seconds, leaped into the air and spun around before splashing, and nearly spooled me. I could not slow that fish down -- it soon broke off.
Probably the longest fish I ever had on the line was a sturgeon. I hired a guide to fish in the Fraser River in British Columbia. We spent a long day on the river with only a single bite. The fish took the bait and moved off slowly. I felt the weight for 10 seconds, then the fish was gone. That fish could have been 7' or more -- I'll never know.
With the prolonged cold weather, I have not been fishing at all this month, and probably will not get back on the water until some time in February. Reminiscing about the good fishing trips I made over the years (such as the ones described above) help to keep me looking ahead to warmer times.