These were likely taken in the American South – perhaps Mississippi or Louisiana. The man in the boat is holding an unbaited trot line. Paddlefish swim the waters with their mouths agape as they filter-feed on zooplankton. They sometimes are caught on bare, set hooks. Passive or accidental snagging was never a reliable fishing method and the fact that these photos were taken shows he thought the catch was worthy of recording.
Sport fishing with treble hooks (trolling or snagging for paddlefish) probably doesn’t pre-date the 1950s. Paddlefish were a common food fish in the Mississippi/Missouri river systems and were obtained by nets before that.
As we noted in Damming the Osage, adult paddlefish can survive, even thrive, in a variety of modified riverine situations, including reservoirs. But the construction of reservoirs destroyed paddlefish spawning grounds, which means they no longer regularly reproduce in the wild. In Missouri, populations are maintained through artificial reproduction at Blind Pony Hatchery.