H20,
with the help of some guides and pictures from this forum I felt pretty comfortable sexing perch especially in the late fall when the egg sac helps confirm females. This link used to show good diagrams and pictures of what the urogenital pore looked like. But photobucket has taken our pictures hostage and added a watermark so sadly the pictures are distorted. There probably are other threads in the archives with better pictures of YP anatomy but with wintertime YP you should be able to confidently separate male from female.

Your YP look very healthy and happy. I'm curious what is in their stomachs if you decide to release to the grease.

see this link:

https://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=375752