Cecil, I think we may lose some perch to natural mortality during spawning time. A few years back, we brought some perch into the lab for spawning studies, and stocked a big female with several males in each aquarium. Several of those big females died after spawning, which has always stuck in my mind. That may be a stressful time when we lose some of the older fish to natural mortality? Perch are a fish that can exhibit high natural mortality rates, even when not harvested by anglers.
Absolutely Dave. I have found stressed or dead females that apparently died in the spawning process or thereafter. I've seen some that appeared have tried to pass their eggs, but the eggs just didn't seem to want to come out completely. It appeared as if they partially were extruded and became water swelled, inhibiting the internal eggs from coming out.
I also think there may be in some cases, an attempt to reabsorb their eggs for whatever reason (in my case no males or few males present may be one reason), or perhaps a sudden drop in water temps. That is quite stressful also. At least I know it is with rainbow trout that reabsorb their eggs due to a lack of the correct spawning conditions.
