what happens to the fish when the river/lake freezes over?

Question

do fish hibernate?

the thing is here where I work there is a larg "man made pond" with a largish gold fish. well the weather has taken us all by serprise and although it isn't fully frozzen I't soon will be... should I be looking for a net and a bowl ice pick?

Answer 1

Good answers so far, but one thing nobody has mentioned yet is oxygen depravation. Unless the pond is extremely shallow - Ice will only form a top layer a few feet thick. This layer however effectively seals off the water from the air interface - preventing oxygen exchange. Amphibians and some turtles will hibernate, but invertebrates and fish will remain active throughout the year.

The fish should live initially, but if there are a lot of fish in your pond, or other animals for that matter, and the ice forms and remains for too long - the available oxygen in the water may be depleted - resulting in a noticable fish kill when the ice melts next spring. Photosynthesis by algae and rooted plants may continue to provide some oxygen as long as the ice is transparent enough to let light through, but thick ice covered with snow pretty much shuts down this process.

This does happen very rarely in small northern lakes and ponds (I'm talking northern Minnesota or Canada here). One trick often used by fisheries agencies is to dump loads of coal dust ontop of the ice. The black dust helps to melt the snow and ice quicker in the spring on suspect lakes.

Answer 2

the fish will swim under the frozen lake/river...a few unfortunate ones will probably be in the wrong place at the wrong time, but for most they will go on w/their normal routines. Except for those few that ice fish, they are safer when the surface is solid.

One of the advantages to all life that is commonly taken for granted is the simple chemistry of ice vs. water. Luckily for us ice is less dense than water. Which means ice floats and does not sink. When the H-o-H freezes air pockets are created b/c of the "frozen state," the molecules stop moving.

Now imagine if frozen water sunk the rivers and seas? What would happen? Remember to consider the depth of the ocean and how much sunlight penetrates the lower level.

Answer 3

Ice is not a good conductor of heat. When the lake freezes the top layer freezez due to outside temperature but as it becomes ice it keeps the inner temperature of the lake. The fish swim inside the lake but if they move toward top they usually feel it cold and return to the warm which is the bed of the lake.
Usually when the lake freezes all the fish move downward and if its a river then usuaully the flow becomes slow and then it becomes hard for fish to travel.

Answer 4

During the cold, only the top layer of the river/lake freezes. Fishes do not hibernate because they are cold-blooded (or adaptive to changes in external temperature) that's why they do well on any season. :)

Answer 5

Only the top layer of the river is frozen to a certain thickness, not the whole river. The fish remains ok further down in the depths.

Answer 6

Only the top freezes. Water is most dense at 4 degrees celcius, so that water keeps sinking to the bottom and the water underneath the ice keeps circulating and won't freeze.

Answer 7

Physics: lakes freeze only on the top, underneath the temperature is 2-3 degrees higher.

Answer 8

most rivers and lakes dont freeze solid , so they just swim slower ,, or like Ive seen some fish will bury them selves in mud untill the ice melts ,,goldfish can withstand really cold water ,,I would not worry about them unless the bottom of the pond is solid ,,

Answer 9

Usually, it is only the surface of the water that freezes over so the fish are okay.

As for whether fish hibernate... that is another question.

Answer 10

even if the lake/river freeze over there is life under the ice . because when the ice is created it has low mass so it flode up and it keep going and create the thick ice layer so under this layer there is water. its mother nature so fish can surrvive in winter..