[sup]Just to cover all bases there have been reports of it raining fish (&frogs).[/sup]
In FL where I live the game fish and wildlife department adds fish to man-made body’s of water. This it’s to combat mosquitoes. Canals, lakes and man made body’s off water are common here. They build long rows of channels of water with rows of soil. The fish eat the insect eggs and naturally controls the insects.
The Northern Snakehead, a predatory Asian fish that has expanded into the Potomac, the Hudson Bay, Arkansas and other locations in the US. Per the US Geological Survey conclusions:
https://www2.usgs.gov/faq/categories/9787/3000%20
Blame the gods!
I wouldn’t rule it out so quickly - in general, birds have a pretty fast digestive transit - which is why so many plants use them successfully to distribute seeds.
Now, fish eggs are not seeds of course, but there are examples of fish eggs that are quite tolerant of other difficult conditions such as dehydration. Like the colonisation of islands by animals surviving on floating debris - It only has to succeed once in a million cases, against the odds, to still be a reality.
Indeed … fish are complete extinct in the State of Oregon …
Mayhaps he’s changed his mind in the 13 years since he posted that. 
OK. I wouldn’t rule it out so slowly.
Dammit zombie threads.
I once had this large plastic container that I used to mix up soil for carnivorous plants, and over time it filled with rain water. I glanced in it once and noticed it moving around and somehow it had been colonized by ostrocods. Don’t know if the eggs were in one or the soil components or were brought in by birds.
Nope, still haven’t changed my mind. You have to keep in mind that seeds are specifically adapted to pass through a given animals digestive system and the conditions encountered there; so they may have physical characteristics making them difficult to mechanically crush and thick “skins” resistant to acid and digestive enzymes for example.
While there are some species of fish whose eggs are hardier than others, they are typically adapted to be resistant to environmental conditions encountered where they evolved. Those eggs may be resistant to desiccation, higher salinity, or limited amounts of freezing or low oxygen environments. I’m not aware of any fish species whose eggs are adapted to resist the mechanical grinding of a birds crop and the chemical digestive process they’d be exposed to after being eaten.
Many species of animals seek out fish eggs as a food source because they are so nutritious and digestible. Resistance or toughness in fish eggs is usually with respect to a few parameters, not all of them.
The idea that I have heard isn’t that it comes from birds swallowing them and pooping them out but simply because the eggs can stick to their feet, bodies or beak and then get redeposited in another place.
I stand by my original statement as well. In the Deep South, you can dig something like a brand new farm pond in a pasture that isn’t connected to anything else and you WILL have fish in it within a few months to a year. Many of them aren’t the types of fish that people stock either. They range from small minnows to sunfish. Bass and catfish (including undesirable mudcats) will show up a little later along with frogs and snakes. Something is putting them there and birds are one of the only explanations that makes sense.
I’m not saying that I think it’s likely, or anywhere near the most common scenario - but I do think it’s probably just about possible under the freakishly right combination of circumstances (which could, I suppose, include such things as health factors in the bird, preventing its digestion from working optimally). Given enough variables and enough rolls of the dice, even the most unlikely outcomes can occasionally pop up.
There’s a lot of quite sensible discussion on the topic here, including a reference to a published paper which claims to have observed viable fish eggs collected from bird feces
How do fish get into man-made lakes?
“Practice, man, practice.”