Are you into animals?  Do you like fish?
Several varieties are recognized by Japan.
What do you mean?  Kinds of fish?  Like koi fish?
They come in many colors such as white, black, red, and blue.
What kinds of things do they eat?  Can they live in saltwater?
Carp's ability to survive and adapt to many water conditions allowed them to travel to Japan.
So, what I'm gathering is that koi fish are descendants of carp?  How are they similar?
Carp were originally bred for color mutations in China.
So Koi are like Japanese Carp.
Color mutations of Carp have occurred across all populations.