Quote Originally Posted by fishingtim View Post
Question for Craig,

When a fish dies in a lake instead of by fillet knife, what determines if the fish will sink to the bottom of the lake or float to the top and wash up to shore? You always see a fish or two dead up along the shoreline, but alot more fish just have to die from old age than the one or two dead ones you see. My best guess was that the fish that die naturally sink to the bottom and never are seen but the fish that die from sickness end up along the shore line blotted.

This came up talking to a buddy about the twenty some pound bass in California "Dottie" that was found on the shoreline a year or so ago. And the white bass fish kill that Cheney or Marion had several years back where fish were scattered on the shoreline.
fishingtim,

Some diseases do cause a fish to "float" at the top of the water as the disease can effect the air bladder of the fish, but not all diseased fish will float and not all fish that die of natural causes will sink.

A big factor in this float/sink question is the temperature, both of the air and the water. At warmer temperatures, decomposition occurs more quickly and will cause a fish carcass to bloat up and come to the service where they are visible. At cold temperatures, decomposition takes place much more slowly and not enough gases may be produced to float the fish to the surface. This is seen in winter roadkills vs. summer roadkills. A roadkill deer will bloat up in a matter of hours in summer but will take days in winter.

Scavengers must also be taken in to consideration as they can clean up dead fish very quickly. Even if they scavengers cannot eat the fish whole, they may make a hole in the skin of the fish which releases the gases floating the fish and the fish will sink. In the summer time fish decompose VERY rapidly and a 5 to 10lb fish is reduced to "soup" in a matter of days.

Easy meals don't last long in the fish world. Sick or dying individuals are picked off quickly by fish or other predators/scavengers. Large scale fish kills produce many easily seen dead individuals, but there are also large numbers that are not easily seen.