Well, what about the system I mentioned? Just have the up and down arrows be little bot detection boxes. My understanding is that all those “I am not a robot” check boxes detect mouse speed, precise click locations, hesitation times, etc. and do a quick calculation on the odds that your clicking behavior was human or robot. I’m probably underestimating what it takes to implement that but on the user side it’s just a click just like any other click.
I mean, you are correct, it was not two fish. But is 64 fish some sort of good sample size?
Follow up question: does this type of thing accumulate in small fish and then concentrate in larger and larger fish?