Because people don't know their real name. They possibly also have got mixed up between Siamese, Chinese, and Japanese. It seems that in the US of A any of those countries are used in conjunction...
Fish ova (eggs) are called roe.
caviar.
Spawning is the production or depositing of large quantities of "roe" in water.
it's caviar. these are the eggs of a sturgeon or certain other fish.