The warm water (20 degrees Celsius) can help grow and mature the fish so that it can be harvested at six years old. The wild sturgeon, also threatened by extinction, can take 20 years before reproduction. The water, which is too warm to discharge into the Kander River is also used to heat a tropical greenhouse. The Tropenhaus farm’s branded 101 Oona caviar sells at about 60 per cent of the price of Beluga caviar from the Caspian Sea.
