Pond Boss Forums MANAGING AN EXISTING POND Evaluating and adjusting fish populations Size Differences in Susceptibility to Extremes

Shorty it very well could be - see the text above on how diet effects cellular workings especially wrt cold tolerance. Also not the lower lethal temps generally for RES. Did you try to age the fish - possible old age mortality?

Redear sunfish, Lepomis microlophm'

Hill et al. (1975) Oklahoma 16.0-26.0 ( 60.8 - 78.8 F)

Still others, particularly the centrarchids, showed

occasional low thermal responsiveness. Fishes

continued to seek increased temperatures until

they succumbed due to physiological inability

to adjust to a rapid increase in temperature in

a steep gradient.

Eric, I did not age those two RES. I stocked 120 RES in the 4-6" size range in December of 2011. My best guess is that those two RES were hatched in the spring of 2010, so six years old, or possibly seven. The other possibility is that those two hatched in my pond in 2012 and were part of my feed training program and some of the select few that I overwintered in 2013-2014.

Shorty,

Did you notice how good the fins look on your two morts? That tells me their demise was quite rapid vs. a gradual one where the fish gets attacked by fungus and other issues leaving the fins in bad shape.

The fins did look in good shape, I would agree, their demise was likely quite rapid. So far those are the only two morts I have seen, I have have to wonder how many never floated.