The last Boto outside South America died on the 21.12.2020 in Duisburg, Germany. It was the last Boto of a group of 5 that came to Duisburg in 1975
According to zoochat, it seems, that there is only one Boto in captivity in an Zoo in Peru left. There was a breeding group in a Zoo in Venezuela that died a couple of years ago.
There were more than 70 river dolphins imported to US Zoos in the 60s and 70s. The last one died in the early 2000s.
All in all, the husbandry of Botos was a disaster. A few of them survived for a long time (usually after their group died), but most of them died after a few months in captivity. A lot of the dolphins died because of rather easily avoidable mistakes like to big group sizes (which resulted in stress and even the dead of some smaller group members in fights), the import of already sick, injured or old animals (which died rather quickly) and inadequate habitats (eg many Botos didn't have a shallow part to sleep on)
It really is a shame how this fascinating and unique animal was treated by us humans