my question is just that…
do they sink or float?
my guess is that once they die they stop breathing and so they sink!
what say?
From my experience with goldfish, they always float. The same applies by human bodies, I believe. Maybe it’s because of the empty space inside the various organs?
- YT
They end up floating, due to gases created as a by-product of the decomposition process. Eventually, I’m sure they sink once the gases are released.
Sua
It depends on why they died. Most fish (e.g., not sharks) have a swim bladder, which is an internal organ that is filled with air, and is regulated by the fish to give it neutral buoyancy. In other word, without the swim bladder, the fish is probably heavier than water. So if the fish dies suddenly, and the swim bladder is unaffected at first, it will retain neutral buoyancy until . . . until something changes. Then the fish will either sink or float, depending on the nature of the internal change. Even a fish that sinks at first (i.e., almost all of them, in my thousands of hours of aquarium experience), will eventually succumb to decomposition, which may also effect the fish’s buoyancy. At which point it may float.
In general, they don’t have time to develop enough gas inside to float. They enter the food chain very quickly.
In all my underwater hours, I have never seen a floating dead fish - although I am sure they exist.
I have seen pieces and remnants on the bottom, as well as sick and hurt fish being savaged.
Something large like a whale or a whale shark would float because it couldn’t be eaten quickly. I have seen a report of a boat damaged by a collision with a dead whale.
I have a goldfish that has an unusual problem: He or she keeps floating to the top of the tank. This fish has to exert energy in order to keep from floating, and when it is at rest, it has no choice but to float, upside down, at the top of the tank. The first time I saw this, I thought the fish was surely dying, but it’s been a few months now so he or she is apparently healthy aside from this quirk! I wonder what causes this and how rare it is. Any fish folks know the answer?
lissener and Diver are right. Depending on how they die, they can float to the surface or sink to the bottom, and, in general, it’s not too long before something else decides to make dinner out of a dead fish in nature. It’s easy for other critters to find and eat dead fish in the water unless something dramatic, like hypoxia or toxic blooms have killed lots of fish and all sorts of other animals in the water.
Here is an example of a fish kill seen from the surface
Here is another example of a fish kill, seen below the surface
Another interesting fact: Whale carcasses are massive resources for benthic critters in the sea; with whole communities based on the carbon and nutrients brought in by dead whales sinking to the bottom. Dead whales have also been known to float and sometimes wash ashore.
Dave,
try slipping a little Bean-o into the fish flakes? I think you just have a weird fish 
As far as dead fish, in all my fishing time, I’ve never seen a dead fish floating on a lake. I assume some do float, but are immediately picked up by birds and/or other fish. Same reason you don’t find many dead animals in the forests. They instantly become a buffet lunch.
He’s probably got a blockage or an infection in his swim bladder; possibly both.
Don’t feed him for 3 or 4 days (don’t worry; it would take approximately 4-6 months for him to starve to death) and then feed him NOTHING but canned peas for a couple weeks: one a day, popped between your fingers, and dropped into the bowl.
And then from now on, only feed him sinking pellets instead of floating pellets or flakes: goldfish tend to gulp air when eating at the surface, which can exacerbate the problem.
And only feed him 2 or 3 times a week from now on: a goldfish’s stomach is about the same size as his eyeball, and his metabolic needs are much, much lower than a warmblooded animal’s. Keep him lean and hungry, and he’ll live a lot longer (the record, last I heard, was 43 years).
What happens to fish when they die? It’s offically known in the fish world as " Sleepin’ wit da mobsters."
As for the floating fish : a friend of mine has a 12 year old gold fish, yes you read that right, 12 year old gold fish that has always floated upside down at the top of the bowl.
Once again, I have nothing of gray matter to contribute.
Carry on.
All I know is they don’t go to heaven.
Fish don’t have souls. Didn’t you go to sunday school?
I remember from the phisteria (sp?) outbreaks amonst fish in the Chesepeake Bay that dead fish float, at least for news reports.
Almost all of my pet fish that died rose to the top initially. But if they died while I was away, they’d decompose and/or be partially eaten, and sink to the bottom.
The notable exception was my wife’s pleco. He was about 30 cm long. When he died, he just lay on the bottom like he normally did. It was tough to tell that he’d died until his eyes started to cloud over. Then I gently nudged him, and yep, he was dead.
He was probably designed not to float, being a bottom-feeder. He looked awfully lean as fish go.
And I thought they all just went to fishy heaven via the toilet bowl.
Guess I was mistaken.
They go to fishy heaven.
If they have a sole.
They become angel fish.
When my town’s river had a toxic spill that killed 117 tons of fish, the gummint hired contractors to rake off and haul away all the dead fish. After a few days, the effort was temporarily called off. The DNR explained that a cold snap had caused all the carcasses to sink to the bottom. When the weather eased, the fish floated again, and the fish-gathering resumed.
Working at a fish hatchery, I remove dead fish from tanks on a daily basis. In the wild, as has already been mentioned, any dead fish is usually eaten up before it can decide to sink or float as long as enough predators are around to eat them. In tanks with nothing to eat them, it depends. Usually fish sink when they die as they are heavier than water. As bacteria start breaking them down, the ones inside the body create gases that cause the fish to start floating; as the fish starts disintegrating on the surface, the bubbles come out, and little bits of fish start falling off and sinking, depending on what bits they are. In warmer (and dirtier) water like aquariums or goldfish bowls, the bacterial activity proceeds faster, and fish start floating sooner; so you might miss seeing them on the bottom (unless the snails start eating them first). In cold water, the whole process is slower, and it takes days for them to start floating (we work at 1 to 15 degrees C). 99% of all the dead fish I pull out of tanks are from the bottom; if we leave them in the water long enough to start floating, someone usually catches %$#@!
Occasionaly if they have a bacterial infection, a dead fish will float as soon as it expires as the little bugs already have a head start.
Johnny L.A. that pun deserves to be scaled, beheaded and gutted.