In an average pond, can water get too warm and make fish stop spawning? I'm sure under controlled conditions one could get the water to warm, heck you could boil fish. A friend of mine ask the question and I couldn't tell him.

Depending on the species - yes , and it can also slow their eating down to a minimum and eventually cause death (aka thermal max).

I sample the discharge bay of a nuclear plant for larval fish. The water temps in the top 3-4 feet can get up over 100F during the summer. We usually catch similar species in the discharge compared to other area but their numbers are greatly reduced.

I would have to say yes in the fact that water could get to hot like ewest said and slow eating down. I have expierenced this first hand this year on my pond. Even to hot maybe to kill some sensative type fish also. From what I been reading thats another reason why you need to be careful when you start to circulate or airate your pond as the water temps in the different levels of the pond could effect your fish as well once you start to mixing it all together.

RC51

Chris, anyone put blue tilapia in the discharge at the lake you sample on with the nuclear plant?

Not that I know of. The water still gets cold in the winter. The lake is on the Arknasas River so there is a lot of flowthrough and the entire lake doesn't have time to heat up.

Chris have there been samples in winter to see how many fish crowd into the warm space?

Not that I know of. My roommate says the threadfins stack in there. I have to take water temps all throughout the year so I will see how much of a difference there is with the water temps.

The lake I fish that has a nuclear plant on it is the only one in the area that can support TFS. If 45 degrees in the lethal temp for blue tilapia, I'd think they might be able to survive in that lake as well. Not much lethal temp difference between blue tilapia and TFS. Or am I wrong on that?

Lake Fairfield in Texas is also a power plant lake and has some pretty impressive tilapia that make it just fine in the winter.

We have warm water discharge power plants on our Great Lakes up here and they definitely are magnets in the winter time for salmonids and other species. of course warm is a relative term and the water is not really that warm in winter once it starts to mix with the frigid water, but warmer than the surrounding water.

About 10 degrees difference in lower lethal temp for TShad (low 40s)and most tilapia ( low 50s)(Blues a little less).