Well, from can be seen around, 95%-99% of TSN in our trade are farm refuse, low quality, poor genes, slower-growing and smaller-growing Pseudoplatystoma fasciatum, often even deformed. They all fall short of 36", usually not exceeding 30", which is still a moot point to the OP but thought I'd share my current conviction.
I am always wary of claims like "Wild caught TSN for sale" unless it comes from a vendor with a bulletproof reputation, honest to the bone and/or verifiable or accountable like our MFK vendors. It's just too easy and too tempting to take a farm cull and label it w/c for 3x-5x higher markup at any point of the collection-export-import-transshipping-sales chain.
It seems almost no vendor wants to mess with w/c TSN when the farm culls abound by millions a dime a dozen literally.