Not all sturgeons live on farms

Not all sturgeon species are farmed in aquaculture. The most common species farmed are the Siberian sturgeon, sterlet, and a hybrid of the Russian and Siberian sturgeon. Russian sturgeon and bester (a hybrid of beluga and sterlet) are a little less common. Beluga, ship sturgeon, and stellate sturgeon are not farmed. For example, for a beluga (the largest of the sturgeons) to produce caviar, it must be up to 17 years old, which is the period of sexual maturity. Waiting so long for aquaculture is a real luxury!
Beluga are not farmed in aquaculture farms. Caviar from these fish is most likely the work of poachers