Its growth/metabolism related. From the other post.

http://www.pondboss.com/cgi-bin/ubbcgi/ultimatebb.cgi?ubb=get_topic;f=20;t=003602


I did some checking. HSB growth in cool water starts (like most warmwater fish) at a point a few degrees higher than when their eating starts to increase. HSB growth slows in fall and starts to increase in spring at 55F+- . That would indicate that solid feeding to support growth would continue down to 50F+- and some feeding to support equilibrium status (maintenance) below that would continue. I have left out the upper (warmer) temps on growth and feeding as they are not applicable to this thread. IIRC this is a few degrees colder than LMB ( 60F growth and 55F feeding for growth). This is of course subject to local genetic conditioning.