Are Exotic fish a danger to small pond?

[Lurker Too]

I had my son at a small pond yesterday, and noticed a 24" coy swimming the bank. With the goldfish looking fish in the muddy water I saw 2 more black fish. Are these carp a danger to the native fish? Could they spawn and if they do wouldn't the fry compete with bluegill for food? I have caught small bass on bottom tight lining worms, and have seen large (bluegill?) nests in 3-5' water, though the last couple of years the drought has seem to reduce the number viewed.

[cricket george]

The koi stick out like a sore thumb and, most likely, the bas will gobble up any spawn. That being said it is best to get them out of the pond