Goldfish ‘Brew’ Alcohol To Make It Through The Winter Without Oxygen

Goldfish 'Brew' Alcohol To Make It Through The Winter Without Oxygen

Goldfish have the rather peculiar ability to make their own alcohol to help them survive harsh winters, but how do they do it in the first place? That question was answered earlier this week by a team of researchers from the Universities of Oslo and Liverpool.

As pointed out by, most vertebrates, humans included, could die if left without oxygen even for a few minutes. But goldfish and crucian carp are unique, as both species of fish are capable of lasting days, or even months in some cases, at the oxygen-free bottom of icy ponds during the winter months. And once the alcohol is created, blood alcohol levels can exceed 50 mg per 100 milliliters, which the researchers observed is far greater than most countries’ thresholds for impaired driving.

The multinational team of researchers discovered that goldfish make alcohol by transforming anaerobically-produced (or oxygen-free) lactic acid into ethanol. This substance then spreads across the fish’s gills and into the water, and prevents lactic acid from building up in their bodies.

In simpler terms, one can interpret this as goldfish getting drunk to survive. And while that might sound preposterous, or like something out of a cartoon, study co-author Michael Berenbrink from the University of Liverpool told Gizmodo that the behavior of goldfish does seem to change after they “brew” their alcohol, though it isn’t sure whether these changes are due to the alcohol or part of a survival strategy.

“Under the ice they try to minimize the energy expenditure. In a way the behavior changes because they’re just sitting there.”

As further noted by, the researchers were able to discover the molecular features that drive the peculiar ability of crucian carp and goldfish to make alcohol. Both species don’t just have one, but rather two sets of proteins that are typically used to help break down carbohydrates within a cell’s mitochondria. One of these sets has a lot in common with the protein sets found in other species, but the second set works whenever there is a lack of oxygen, and features a mutation that allows for the creation of ethanol outside the mitochondria.

Based on genetic analysis performed on the protein sets, this unusual feature came about as a result of a “genome duplication event” that took place about 8 million years ago in a common ancestor of goldfish and crucian carp.

In a statement, lead author Cathrine Elisabeth Fagernes from the University of Oslo said that the ability of crucian carp and goldfish to produce alcohol helps them emerge as sole survivors in harsh winter environments. That allows them to avoid competition with other fish species, and the threat of being preyed upon by these creatures.

“It’s no wonder then that the crucian carp’s cousin, the goldfish, is arguably one of the most resilient pets under human care,” Fagernes added.

[Featured Image by dien/Shutterstock]