Bruce - In addition to what Cecil said "Only mortality I have experienced is female spawning mortality and that is very minimal and happens in wild populations too." Occassionally in, midsummer in certain ponds stocked with perch near me, we will see some late July - August mortalities of largest perch. I am not sure yet if this is due to temperature or oxygen. I think it may be primarily due to temperature-oxygen combination as the perch seek coolest water when surface temps are in the mid to high 80's or low 90's. Not all local perch ponds experience this problem and I think the strain of perch brood stock also plays a role with this topic. Smaller perch have been reported to tolerate higher temperatures than the largest and oldest individuals.
