From all the research I have found on cold tolerance, Blues handle the lowest temps, followed closely by Hybrid Reds, and then about 5 degree higher is the nile. The red hybrid of blue and nile has the most marketable meat but slower growth than the fastest growing nile but still not as fast as the blue and not as cold tolerant as the blue.
This was the reason I chose to go with the Blues to raise as pond forage--although not as rapid growth as the nile, it is close and the lower cold tolerance could increase the life expectancy in colder waters by a month or more.
