When using a starvation-ranching pacu design, when the player is watching an asteroid, each pacu on that asteroid will produce one egg over its lifetime even if completely unfed. This allows keeping a stable population of pacus in a single tile of water, producing pacu filets whenever a pacu dies for an infinite source. However, when watching another asteroid (in my case the superconductive asteroid) the population of pacus will decline. I think this has something to do with automation of unfocused asteroids, but I'm not sure if this is an issue with the reproduction rate changing relative to the death age of the pacus, or an issue with pacus just being straight-up deleted for being too many in a tile.
I started this save before the Sweet Dreams update, and I didn't notice the issue happening before Sweet Dreams, but I'm not 100% certain that it's a new issue, I just might not have noticed.
1. Place many domesticated pacus in a single tile of water with lifespans that do not synchronize exactly
2. Wait for 25-50 cycles and see the population stays roughly the same (there will be some increase because of the period between laying an egg and dying, but population should not decrease below initial)
3. Switch to viewing another asteroid besides the one with the pacus and wait 5-10 cycles
4. Return to the original asteroid and observe the population decreased