I am needed ideas for what might have killed hundreds of fry's in our local city pond... It had plenty of O2 has bass, bluegill and bullhead cats. Went fishing today and saw hundred's fry's along the banks dead. However the problem is that they were almost eaten and spit out. There was nothing left but a tail and scales. Any Idea's thanks

Strange...sometimes bass will gourge themselves on fry like bullheads and regurgitate some from overeating presumably....but you're seeing hundreds?

If it were chemicals or O2 you would see larger fish, older fish taking the hit.

Can you identify them or are they too far gone?

Maybe it's just because I'm in the management business, but I think that "chemicals" get a bad name. Looking at Wikipedia, a "chemical" is something that is pure or that is of a known chemical composition. So from the O2 that we breath to the H2O that we drink, they are all chemicals, but I digress.
Fish are effected by materials that are in solution on a gram per milligram basis. With Toxins small fish are effected first, this is because even though the toxins may have reached the same concentration over the water body but because smaller fish have fewer grams of body weight it takes fewer milligrams of the toxin to kill that fish. Larger fish have larger body mass and therefore require a longer exposure time for the toxin to accumulate in their body, not all toxins will accumulate and some are processed faster than they can build-up, this could be the reason that bigger fish are often not effected when smaller fish are.
When it comes to Oxygen the same thing is true but in reverse. Larger fish require a higher volume of oxygen to fuel their larger bodies and are typically the first to die when the O2 levels dip. So it's highly unlikely that a O2 shortage caused the fry to float up but there's no real way to determine the cause of death so I would just keep an eye out and see if you notice any more over the next week or so before you get too worried about it.

they are too far gone. Even since seeing them dead I havent see any fry's in the water. I have told the park mgmnt about it however they have no clue and will be calling out a lake dr. to figure out what is going on and how to stop it.