I found these in my pond last week and don't know if they are koi fry or something else. In addition to my koi, I have two oscars and several plecostomuses (plecostomi?) in the pond. Out of my dozen koi, most are male and three or four female. A couple of the females look egg heavy (wide belly/hip area), but they haven't seemed to get suddenly thinner, and I've seen no eggs.
https://youtu.be/4_sL0dgmN9c