I got to spend three weeks in Japan this summer after winning the JETS Fan Fund to send a European SF fan to the World Science Fiction convention in Yokohama. While I was there I got to the fish market one morning around 9am, and there was still *plenty* to see ... the wholesale market (which is offlimits to tourists) was closed, but they were still using bandsaws on fish and the little bikes and vehicles were still zooming around.
And there are little local "cafe-style" sushi shops right there with the best sushi I've ever tasted at a very reasonable price (about $20 for 8 different pieces, which were *superb*)
I also took several hundred photos of the fish market which will be going up with the rest of the trip report sometime in the next few weeks. I'll try to get some up tonight/tomorrow if I can.
http://www.flickr.com/photos/the_magician/