General Question

buster's avatar

Why do dead fish float?

Asked by buster (10269points) May 1st, 2008
Observing members: 0 Composing members: 0

13 Answers

Response moderated
brownlemur's avatar

Gas buildup.

Alina1235's avatar

its funny and sad at the same time. But same reason why dead human float too

MrKnowItAll's avatar

MrKnowItAll would like to know why the moderators are being so heavy handed. I saw the above posting and I declare it to be ok.

Please use a little better judgment next time.

brownlemur's avatar

[moderator says]: the quip was removed for unnecessary obscenity and for not actually answering the question. Your advice is duly noted but I am disinclined to acquiesce to your request.

delirium's avatar

(I had a POTC moment reading your second response, lemur.)

And brownlemur’s first response is totally correct. Its the same reason, actually, that a body dumped in a body (ha) of water will surface later.

If you want to test this, take the dead fish and split it down the middle. If you’ve split it right, it will sink.

delirium's avatar

Alina, I hadn’t seen that you said the same thing above me. Sorry to repeat.

akeil's avatar

Bacteria that feed on dead flesh produce lots of gas (bacterial farts, in a sense, and usually stinky gases, like methane). When those gases can’t escape the fish it floats because it bloats and becomes less dense than the water.

MrKnowItAll's avatar

MrKnowItAll finds the sorting of obscenities as necessary or unnecessary to be an interesting concept.

Alina1235's avatar

delirium…. I read up on the article you posted about human flesh. I’m very interested in thing like that. Especially in your line of work.
Ps. Thanks for the piece of knowledge!

El_Cadejo's avatar

Not all dead fish float. The floating is actually caused by their swim bladder. This is what is used to control the depth at which the fish is swimming. When fish dive deeper oxygen is being diffused into the blood of the fish and then out the gills. Where as when a fish rises oxygen is being taken into the bladder. Obviously when a fish dies it has no more control over this(thats not saying he did before(its a chemical response depending on the pressure surrounding the fish)) So depending on the amount of oxygen in the bladder at the time of death the fish will either A. float immediately to the top(lots of oxygen) or B. sink to the bottom and wait for the gases to build up(little oxygen). This also explains why the fish are usually found floating belly up.

Del it has nothing to do with perfectly cutting the fish in half you just have to hit the bladder. I occasionally have this problem with fish that i feed to my shrimp just give them a little squeeze to pop the bladder and then it will sink right to the bottom.

delirium's avatar

Interesting! That’s what I get for assuming dead things are similar to each other.

zaid's avatar

cause if not they’d drown?

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