Of course, they don't do it by drinking Scotch.
Humans are known to toss back a strong tipple on a cold day to feel warmer—though those positive effects are actually a bit of a myth. However, a new study suggests that for goldfish, alcohol really is the magic elixir that can help them survive freezing waters—to the point where these household pets and their wild counterparts produce legally-intoxicating levels of alcohol in their bodies to stay alive.
Scientists have known for some time that goldfish can produce their own alcohol, but specifics of how and why were still a bit of a mystery. A recently published study with the intense title of “Extreme anoxia tolerance in crucian carp and goldfish through neofunctionalization of duplicated genes creating a new ethanol-producing pyruvate decarboxylase pathway” has a very simple explanation: Goldfish can get themselves drunk to live. The actual science, however, is far more complex. In frozen water conditions, oxygen levels drop below the point where most vertebrates would be able to survive: Consuming carbohydrates without oxygen creates lactic acid, the buildup of which can be deadly. But goldfish and crucian carp have developed a second set of proteins that allows them to process this lactic acid into alcohol which, though intoxicating, isn’t toxic to the point of killing them.
“The second pathway is only activated through lack of oxygen,” the University of Liverpool’s Michael Berenbrink, one of the study’s authors, told the BBC. “The ice cover closes them off from the air, so when the pond is ice-covered the fish consumes all the oxygen and then it switches over to the alcohol.” The longer they are in these oxygen-less conditions, the higher those alcohol levels become. “If you measure them in the field the blood alcohol goes up above 50mg per 100 milliliters, which is the [drunk driving] limit in Scotland and northern European countries,” Berenbrink continued. “So they are really 'under the influence.’”
Though totally impractical, Berenbrink even calculated how long it would take to make a sort of “goldfish beer” using this natural process. “If you put them in a beer glass and closed them off, it would take 200 days to get it up to 4%,” he said. “In nature, it just would not happen,” he unfortunately added—but don’t let that stop you from dreaming of some sort of mythical carp-filled lake of booze! And in the meantime, there's lobster beer and fried chicken beer to tide you over.