Hong Kong, Jan. 8 -- In his waders, Stefan Astner checks on the albino sturgeon: Almost two decades after they hatched, they're ready to be gutted for their white caviar to be shipped out. "The fish have already been through the ultrasound so we saw that they are full (of roe) and they will go into production soon," Astner says, dipping his net into a small pond teeming with the rare, white sturgeon.

Deemed the most expensive food in the world, demand for caviar - essentially, salted roe - has driven most sturgeon species to the brink of extinction in the wild. But fish farms like the one where Astner works in the village of Groedig, near the Austrian city of Salzburg, offer a more sustainable alternative. Walter Gruell, fish farmer and ...