Bruce,
I'm shooting for the mid 70's.
Below is from the NRAC "White Paper" on Yellow Perch. I've highlighted pertinent info.
http://ag.ansc.purdue.edu/aquanic/ncrac/wpapers/YellowPerch11-21-03.htm Grow-out Methods
One of the most important factors for the successful grow out of any fish species is the availability of water at the temperature needed to promote good growth. It has long been established that the optimum temperature for the growth of yellow perch is 73-77°F (23-25°C).
Yellow Perch show little or no growth at temperatures below 50 F. (10 C) At temperatures above 79°F (26°C) they show signs of stress and reduced growth, disease, and mortalities can be expected under conventional aquaculture conditions. Yellow perch reared unconfined in ponds seem able to tolerate temperatures up to 79°F (26°C), provided that other water quality parameters are acceptable. Under higher density conditions such as in net-pens and tanks, however, stress and/or disease problems frequently become apparent at temperatures above 70-72°F (21-22°C). These facts greatly impact the four feasible methods for raising yellow perch to market size: (1) flow-through systems, (2) water recirculation systems, (3) net-pens, and (4) open pond culture. As of 2003, one major study funded by NCRAC has as its goal to document production parameters and real costs for raising yellow perch to market size in different production systems.
