Uninvited guests The Hudson River has been invaded...by fish. These non-native species are either unwanted guests or purposeful introductions from other parts of the world. The common carp, introduced from Asia, has been in the river for over a hundred years. Carp can uproot vegetation, muddy the water, and eat native fish eggs. Goldfish released from aquariums can now be found in the Hudson. Other invasive plants and animals, such as the water chestnut and the zebra mussel, have disrupted the river’s ecology and cost lots of money to control.