Wow, I never knew.  This is a great article, and for the more science minded, read the entire research paper.  Both article and research links provided below. 
 
"Every winter, the northern European crucian carp gets frozen into the ice, and receives no oxygen. Every spring, when the ice melts, a seeming miracle occurs: the fish emerges from the ice and resumes normal life....

Or, not quite. When they thaw from their winter freeze, the crucian carp's brain is not quite the same, according to new research. But the same researchers also found that the fish can recover from its months of anoxia."
 
Article form Science Alert - https://www.sciencealert.com/fish-can-recover-brain-damage-frozen-withou...
 
Research paper from Journal of Experimental Biology: Re-oxygenation after anoxia induces brain cell death and memory loss in the anoxia-tolerant crucian carp  https://journals.biologists.com/jeb/article/220/21/3883/33753/Re-oxygena...