The diversity of fish species in America is in serious decline, according to new research published in today’s issue of the journal Science. Small populations of native fish have gone extinct while popular food and game fish have been spread by humans, leading fish populations across the country to become less diverse. In recent years, government-sanctioned introductions of game fish have declined, but illegal and inadvertent introductions have continued. For example, the Eurasian goldfish is not native to the U.S., but it is now found in lakes and streams of 42 states thanks to people who decided they no longer wanted the fish as pets and released them into the wild.