The popular Tsukiji fish market, in its current incarnation, still has a couple of months left until it packs up and moves to Toyosu on October 11, 2018. Along with a general rise in tourist numbers, the drawn-out saga of the fish market's relocation (which includes anything from 'will-it-move-actually-it-isn't-actually-it-is' to more mouldy tales) seems to have spurred visitor numbers to new heights. As such, the Tokyo Metropolitan Government has decided to push back the time that non-buyers/visitors can enter the inner market from 10am to 11am effective June 15, 2018, the Asahi Shimbun reported.
Friction between vendors and visitors has existed for quite some time now, and it's not the first time the market has had to clamp down: the famed tuna auction was completely off-limits to tourists for at least a month or two in the winter of 2008 and 2009 due to visitors trying to touch the tuna; one drunk British tourist even tried to lick one. The inner market, with its maze of vendors and trolleys zigzagging along at high speeds, has had a no-visitor-before-9am policy for years, which was upped to 10am in 2010.
Between 8am and 10am is considered the busiest period for vendors; by the time visitors are allowed in, most businesses would have winded down. Note that the tuna auction is not affected, although there is still the cap of 120 visitors for that one.
So for the inner market, please stick to the new 11am time starting June 15. But that shouldn't affect you much, because all the food, snacks and souvenirs (especially the sushi restaurants) are all located in the outer market. This means you can still head to the (outer) market for an early ready-to-eat snack and breakfast.