A percentage of grass carp do reproduce. When they create they "sterile" version, some do not actually get the extra set of chromosomes to make them sterile. Thats why there are Diploid ( fertile) and tripliod (strerile) strains. Either thru temperature shock or Uv lighting, the fertilized egg is believed to have been sterilized but there is no way of telling untill the fish is hatched. By then they are all mixed up so there is a small perentage that are capable of breeding. The news guys are not technically wrong for calling them "Asian carp " really. They are from The Armur River basin in East Asia and that is where they get their name "White Amur". I believe they just used "Asian " as an attention grabber.