I was curious about this as well, so I did a search. Even though I love sushi, I don't think I'd want to risk my life eating this fish- not to mention the ethical issues surrounding the harvest of Fugu.
I came upon an article on American.edu- never heard of the site, but the article says this about Fugu farming:
"The best season for fugu dishes is during the winter. Therefore,
there is a large difference in prices over the seasons. Japan has
been successful in artificial cultivation of fugu. Fishers catch
fugu in spring because it is the spawning season. Then, they
cultivate these fish in a cage in the sea. They raise fish until
the price goes up and start selling fugu in the fish market in
late fall. Fugu are sold while they are alive, therefore,
transportation for fugu is exclusively arranged. The fugu's mouth
are stitched shut because fugu tend to fight with each other in a
small space."
UGH! That really, really (no... REALLY) upsets this puffer-lover. I'm not sure how accurate this information is, but you can read the entire article here:
http://www1.american.edu/TED/blowfish.htm
Hope this helps! ~Gracie