The bit about the 400lb blue catfish. The information about fisheries management and Rafanesque-Shmaltz's biography are easy enough to find. (Thanks for getting me to look him up, he's really interesting.)
I said 250-300.
I got those numbers from the Planet Catfish article on blue cats. Most of Rafinesque's works are in French, which I cannot read. PCF is compiled by better minds than me, namely Julian Dignall and Dr. Heok Hee Ng. If they report it, I tend to believe it.
The exact text:
This is North America's largest native fish. Recent sports fishing records show this fish weighing well over 100 pounds, with a world record as of June 2011 of 143 pounds and 57 inches in length. In recent times, the fish is seriously overfished, records from before the year 1900 range from 200 to 300 pounds. Rafinesque, a noted naturalist, claimed to have seen a specimen at 250 pounds.
Link:
https://www.planetcatfish.com/common/species.php?species_id=261