ive seen some strange behaviour from fish in my pond, more so over winter.
2 years ago i had probebly 4-5 inches of ice on my pond, i did have a airstone going to keep a small corner ice free, however i was totally gutted to see one of my prize koi on its side on the bottom looking dead. it was far under the ice and i couldnt get my net through the small hole, so rather than smash the ice to get it out, and spook all the other fish, i thought id leave it a few days as we were due some warmer weather.
well 3 or 4 days later when the ice was thin enuff (and the fish still on its side in the same spot!) i broke a small hole (enuff to get my arm in) i reached down to grab the fish and as i touched it it swam away!! i shit myself i can tell you!
its still swimming around happy as i type!
weird!