I used to be a skeptic about birds transferring fish or fish eggs to other ponds but I am now a believer. Why? Because a friend and manager of one branch of the largest ornamental fish farms in the country says it not only happens, but he has evidence of it. (Ozark Valley Fisheries)
In their 200 ponds in Martinsville, Indiana they grow out some unusual gold fish and koi varities that ARE NOT sold locally. Furthermore these fish are aquarium fish that are too expensive to be planted into outdoor ponds even if they were available locally. But yet they are showing up in nearby private ponds up to several miles away. He maintains that since the eggs are quite sticky and the farm gets visted by hundered of herons and ducks a year, he believes the eggs may be sticking to the webbed feed of visiting birds and transferred to nearby ponds. He admits the odds are against it but considering the birds fold up their webbed feet, or even tuck them in as with ducks that may keep the eggs moist albeit for a short amount of time. It wouldn't be a stretch to assume at least one egg could make it to a nearby pond alive. After the fish become established in that pond the same process could take them to another and so forth.
Considering the high fecundity of the carp family, and it only takes one egg to produce one ifsh and two to potentially produce a male and female I'm a believer. As far as other species I really don't know.
Some of you many not be aware of this but you can ship trout eggs fertilized or unfertilized without any water as long as you keep them cool and moist. Why would other fish eggs be any different?
