Baby fish are initially called larvae, then fry and finally fingerlings before they mature into adult fish. Larvae are totally dependent on their yolk sac, while fry are able to feed themselves. Fingerlings have functional fins and scales that are comparable to adult fish anatomy, unlike fry.
Larval fish, eggs and fry are also known as ichthyoplankton, which literally means "drifting fish," because they are largely incapable of directing their own motion. Instead, they drift in the current until they develop fins. Fingerlings are the juvenile stage that is roughly the size of a human finger in the case of moderately-sized fish such as salmon, hence their name.