Here are some photos of a tarpon caught in Lake Pontchartrain off the Mandeville lakefront. Apparently it happened often enough that people weren't that surprised, but it did happen rarely enough that it merited a photograph in the newspaper.
And here is a photo of a man with two tarpons, one being 125 lbs, that was caught in the Tchefuncte River near Covington.
Tarpon caught in mouth of Tchefuncte River in 1940 (above)
Here's a photo of the Mandeville Inn and some local folks and visitors, showing off a tarpon that had just been caught in Lake Pontchartrain.