Dear EarthTalk: What exactly are Asian carp, and why are they such a big problem lately? Introduced in the southeast to help control weeds and parasites in aquaculture operations, these fish soon spread up the Mississippi River system where they have been crowding out native fish populations not used to competing with such aggressive invaders. Asian carp are hardy, lay hundreds of thousands of eggs at a time and spread into new habitat quickly and easily. To wit, they can jump over barriers such as low dams. Also, flooding has united states asian carp invasive species the fish expand into previously unattainable water bodies.