If a pond freezes solid, and it has fish in it, do the fish freeze, and then in the spring come alive again, or do they die because the have frozen?

shayla wrote:

If a pond freezes solid, and it has fish in it, do the fish freeze, and then in the spring come alive again, or do they die because the have frozen?

Most fish would die.  However, in a climate like ours, few ponds of a size large enough to hold a permernant popultion of fish will freeze entirely.  Water is an odd substance, in that when frozen, it's actually less dense than when liquid.  As such, when water freezes, the ice covers the top first.  This then ges some way to insulating the water below, meaning most large ponds will remain liquid at the bottom, and the fish can survive.

Last edited by Peter Falkingham (26th Feb 2008 14:41:22)

So in that situation if a pond stayed frozen for many weeks (unlikely in UK I know) how do the fish survive? They have poor thermoregulation and as their core body temperature gets close the freezing they must become very slow and eat little but what about oxygen - at some point does that become a limiting factor?

Last edited by David Wynick (27th Feb 2008 08:45:59)

As the fish become less active their requirement for oxygen decreases, which reduces the problem. Also, colder water holds more oxygen in solution, so any oxygen trapped under the ice is more readily available to the fish (who don't need as much...).