They lack gills, they give birth to live babies (not eggs).
An animal that can give birth is a female organism. Males can't give birth because they don't have the appropriate organs.
Fish are animals that have gills.
A fawn.
Horse
Boy animals do not give birth. The only animal that can even closely do that is the male seahorse, but it technically does not give birth. It just stores the eggs in its pouch.
Gills
Like all dogs it gives birth to a live animal
Gills allow animals to breath underwater.
It means that the animal will give birth to live young. Mammals are live-bearing. If an animal gives birth to eggs, it is not.
Fish.
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