1. I highly doubt he was successful in doing so (kept it for more than a year and it approached > 80% of wild size)
2. Even if it has happened, a bull shark can somewhat live in freshwater so the guy didn't have to worry about maintaining salinity.
Just cause a vendor brings it in doesn't mean that people have successfully kept it. It just means people are willing to buy it. I highly doubt the bumblebee groupers are anywhere near adult size.
Just cause someone kept it doesn't really mean much. The burden of proof lies in proving that they were kept successfully