Fish
Crucian Carp
Carassius carassius
Under the ice of a winter pond with no oxygen left in the water, a crucian carp lies almost motionless, alive on a chemistry trick few other vertebrates can manage.
Overview
The crucian carp, Carassius carassius, is a Least Concern carp of small, weedy ponds and slow waters across central and northern Europe and into Asia. Its lack of barbels, its deep golden body, and its ability to live without oxygen make it one of the toughest pond fish in the world.
A fish that brews its own antifreeze
By turning lactic acid into ethanol and releasing it across its gills, the crucian carp avoids the poisoning that would kill most animals in the same water.
Status
Least Concern, though pure populations have declined in places.
Crucian Carp: common questions
How can you tell a crucian carp from a common carp?
It has no barbels around its mouth, and a deeper, rounder body with a convex dorsal fin.
How does a crucian carp survive under ice?
In oxygen-free water it converts lactic acid into ethanol, which it releases across its gills, so it can survive for months.
Does the crucian carp change shape?
Yes, where predators such as pike are present, it grows a deeper body, which makes it harder to swallow.
Where is the crucian carp found?
It lives in small ponds, lakes, and slow waters across central and northern Europe and into Asia.