In Fear of a Bot Planet, the robot mayor says they have had 146000 + straight Human Hunts without finding any humans... If they are holding one every day at 5 pm. that would be something like 3000 years!? What, they used to hold more then one a day??
Well, you have to keep in mind that the length of a day and a year aren't necessarily the same on alien worlds as they are on Earth. Still, more than one a day is probably likely.
In a Fishful of Dollars Zoidberg breaks down and admits his people ate all the anchovies; they way he talks it sounds like he umm,helped some in making them extinct.
Some kind of racial memory, I suppose. Or maybe they aren't extinct on Decapod 10.