Could it be possible.........these fish are a victim of their own success?
Follow along with my thinking process and see if the logic makes sense.
What if the fish were simply too fat, the fat stiffened up in extremely cold weather, and the fish muscles couldn't move so the fish suffocated?
Not saying this is the case. Just a hypothesis from a non expert.
but here is some info on the process.
The ability of a fish to alter its lipid composition when placed in colder water is one factor that determines survival. The death of these fish is thought to be a result of the fat that the goldfish consume or produce (Mitchell 1990). Goldfish with high concentrations of saturated body fat are less tolerant of temperature change than fish with high concentrations of unsaturated body fat. Similarly, rainbow trout Oncorhynhcus mykiss that have been fed diets high in saturated fats stiffen and die when placed in cold water (Mitchell 1990). In these fish, the fat apparently hardens in the colder water, causing the fat-impregnated muscles to stiffen and the fish to become exhausted and lose movement. This differs between species and likely between BG and CNBG.
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