burgerm - once the water temps drop below 55 and especially 50F, warmwater fish growth is very slow, if it even occurs. ML can verify this by measuring his GGs next spring. And at 39-40F growth, for all practical purposes essentially stops. However fish will definately feed in these cold water temps. Amount of feeding will be temperature dependant. The intake of food will be substantially less than during periods of warmer water. Keep in mind that fish are cold blooded animals and all the basic rules of poikilotherm metabolism apply to them. The intake of food at these lower temps is basically used to maintain body condition and or fat reserves.
Heavy feeding of warm water fish at water temperatures below 45F have been known to cause fish deaths in northern waters due to the fish having difficulty of digesting lots of dry, artificial feed. One fish farmer told me the deaths were due to the food developing bacterial spoilage in the stomach before it could be digested in the cold temperatures. I feed my fish (moist food) including some of those in a cage very lightly in cold water and I have never observed problems of feeding and cold-water deaths. I do not know if moist or dry food has any affect regarding fish feeding and mortalities in cold water.
Bruce Condello (posted in Cecil Envy) is currently feeding yellow perch fairly high amounts of dry food in cold water of around 52F-55F. He has not observed any mortality so far. Bruce thinks the yellow perch are even showing signs of growth. Keep in mind that yellow perch are classed as cool water fish and not warm water fish. Yellow perch undergo a lot of egg development & sexual maturation during winter. They feed actively during winter at 39-40F. They spawn soon after ice out at water temps of 48-54F.
