Not sure about every brand (there's over 2000 caviar farms apparently) but a few I found:
https://www.greatbritishchefs.com/features/ethical-caviar-fa...
https://californiacaviar.com/pages/our-story
https://www.finedininglovers.com/article/meet-frances-no-kil...
Not killing the fish is an obvious way to increase the farm's yield so I imagine most producers are interested in it. Sturgeon meat isn't particularly demanded either...