Bruce,

Makes perfect sense to me. I have literature (The Yellow Perch Culture Guide NCRAC Culture Series # 103 October 2006) that says, "Yellow perch are more tolerant to low dissolved oxygen than sunfish. Reports have indicated dissolved oxygen levels as low as 3.5 mg/l (ppm) for 67 days will not be detrimental to perch growth."

But when it comes to temps it says, "Yellow Perch are deemed a cool water fish and show a preference for water temps between 21-24 C. (70 to 75); they have a physiological optimum temp of 22 to 24 C. (72 to 75 F.). Upper lethal temperatures for yellow perch have been reported as 26 - 30 C. (79-86 F.)."

My big pond that I have grown out some big ones in gets up into the low 80's in really hot weather. (Apparently the low 70 degree water that flows in does do some modification of temps.) With good mixing by the diffusers it only drops to 79 at about 9 feet. When the water gets that warm I don't see any perch feeding (rarely did anyway), and when I did catch them in deep water, if I handled them by just pressing slightly on the gill covers their gills would hemmorage. That tells me they were stressed and probably seek out cooler pockets on the bottom an wait out the heat. I've seen literature here that say at the upper temp limits they can't take any handling whatsoever.

http://www.thefishsite.com/articles/241/species-profile-yellow-perch-perca-flavescens



Here's your solution: Dig a small steep sided 1/10th acre pond upstream of your dad's pond. pump 45 gpms into that pond and over flow that into your dad's pond like I do, to keep temps in the low 70's. But if you went this route you may want to drain your dad's pond and make sure that it too is steep sided with no shallow areas to allow the pond to warm up fast.

This would give you a great excuse to have a trout pond! \:D

See there's a silver lining to everything! \:D

If pigs could fly bacon would be harder to come by and there would be a lot of damaged trees.